File "misuse-of-formulas.html"
Path: /ThinkIB/chem/chemistry/page/32586/misuse-of-formulashtml
File size: 107.92 KB
MIME-type: text/html
Charset: utf-8
<!DOCTYPE html>
<html lang="en">
<head>
<!-- Google Tag Manager -->
<script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
})(window,document,'script','dataLayer','GTM-K5VSFSN');
</script>
<!-- End Google Tag Manager -->
<meta http-equiv="x-ua-compatible" content="IE=Edge">
<title>DP Chemistry: Misuse of formulas</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="robots" content="index, follow"><meta name="googlebot" content="noarchive">
<!-- Removed by WebCopy --><!--<base href="https://www.thinkib.net">--><!-- Removed by WebCopy --><meta name="keywords" content="chemistry, inthinking, IB, IBDP, IBMYP, thinkib, baccalaureate, education"><meta name="description" content="Students often use mathematical formulas to solve chemical problems in exams and sometimes arrive at the wrong answer. This page looks at why this is so and encourages students to work always from first principles rather than mindlessly "plug" values into a formula that they are unable to derive for themselves. It gives worked examples and provides some further practice questions with worked answers.Both mathematics..."><meta prefix="og: http://ogp.me/ns#" property="og:title" name="og:title" content="DP Chemistry: Misuse of formulas">
<meta prefix="og: http://ogp.me/ns#" property="og:image" content="media/ib/chemistry/images/2014 Exams/m1v1=m2v2.png">
<meta prefix="og: http://ogp.me/ns#" property="og:description" name="og:description" content="Students often use mathematical formulas to solve chemical problems in exams and sometimes arrive at the wrong answer. This page looks at why this is so and encourages students to work always from first principles rather than mindlessly "plug" values into a formula that they are unable to derive for themselves. It gives worked examples and provides some further practice questions with worked answers.Both mathematics...">
<meta prefix="og: http://ogp.me/ns#" property="og:url" name="og:url" content="https://www.thinkib.net/chemistry/page/32586/misuse-of-formulas">
<meta prefix="og: http://ogp.me/ns#" property="og:site_name" name="og:site_name" content="Subscription websites for IB teachers & their classes">
<meta prefix="og: http://ogp.me/ns#" property="og:locale" name="og:locale" content="en">
<meta prefix="og: http://ogp.me/ns#" property="og:type" name="og:type" content="website">
<meta name="description" content="Students often use mathematical formulas to solve chemical problems in exams and sometimes arrive at the wrong answer. This page looks at why this is so and encourages students to work always from first principles rather than mindlessly "plug" values into a formula that they are unable to derive for themselves. It gives worked examples and provides some further practice questions with worked answers.Both mathematics...">
<meta name="image" content="media/ib/chemistry/images/2014 Exams/m1v1=m2v2.png">
<meta name="keywords" content="Chemistry, Inthinking, IB, IBDP, IBMYP, Thinkib, Baccalaureate, Education, inthinking, thinkib, baccalaureate, education, diploma, international baccalaureate, international schools, high school degree, middle years, middle years programme, international education, IB diploma">
<meta itemprop="name" content="DP Chemistry: Misuse of formulas">
<meta itemprop="description" content="Students often use mathematical formulas to solve chemical problems in exams and sometimes arrive at the wrong answer. This page looks at why this is so and encourages students to work always from first principles rather than mindlessly "plug" values into a formula that they are unable to derive for themselves. It gives worked examples and provides some further practice questions with worked answers.Both mathematics...">
<meta itemprop="image" content="media/ib/chemistry/images/2014 Exams/m1v1=m2v2.png">
<meta name="twitter:card" content="summary_large_image">
<meta name="twitter:title" content="DP Chemistry: Misuse of formulas">
<meta name="twitter:description" content="Students often use mathematical formulas to solve chemical problems in exams and sometimes arrive at the wrong answer. This page looks at why this is so and encourages students to work always from first principles rather than mindlessly "plug" values into a formula that they are unable to derive for themselves. It gives worked examples and provides some further practice questions with worked answers.Both mathematics...">
<meta name="twitter:image" content="media/ib/chemistry/images/2014 Exams/m1v1=m2v2.png">
<meta name="twitter:creator" content="@InThinker">
<link href="../../../css/bootstrap.min-1.css" rel="stylesheet" media="screen">
<link href="../../../css/font-awesome-4.7.0/css/font-awesome.min-1.css" rel="stylesheet">
<link href="../../../css/top-nav.min-1.css?v=202211301945" rel="stylesheet" media="screen">
<link href="../../../css/style.min-1.css?v=202212191040" rel="stylesheet" media="screen">
<link href="../../../css/style-ib.min-1.css?v=202211282000" rel="stylesheet" media="screen">
<link rel="stylesheet" type="text/css" href="../../../js/jq-fancybox/jquery.fancybox.min-1.css">
<link href="../../../js/jq-fancybox/jquery.fancybox.min-1.css" type="text/css" rel="stylesheet">
<script>function inIframe () {try {return window.self !== window.top;} catch (e) {return true;}}if( inIframe() ) { window.location.href = "/mb/embed?mbtest=1&ref=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas"; }</script><link rel="stylesheet" href="../../../assets/css/ckeditor5-custom-1.css" type="text/css"><link rel="stylesheet" href="../../../css/snippets.min-1.css?v=202210181500"><link rel="stylesheet" href="../../../css/article.min-1.css?v=202212151220"><link rel="stylesheet" href="../../../css/toplevel-map-1.css"><link rel="stylesheet" href="../../../css/side-nav.min-1.css?v=20220520"><script src="../../../js/localdates.min-1.js?v=202009290900"></script><script src="../../../js/ifvisible.min-1.js"></script><script>ifvisible.setIdleDuration(300);</script><script>var tibSitename = "chemistry";</script>
<script>
const SITE_TAG = "ib"
const SITE_WEB = "ThinkIB.net"
const SITE_DOMAIN = "www.thinkib.net"
const SITE_URI = "https://thinkib.net"
const SITE_CLIENT_CODE = "TIB000001"
let imageThinker = "../../../img/header-thinker-ib.svg";
let imageStudent = "img/header-student-thinkib.svg";
</script>
<script>var userHash = "IB Docs (2) Team", userTicket = "IB Docs (2) Team";</script><script src="../../../js/user/local-stats.min-1.js?v=202102101800"></script><link rel="apple-touch-icon-precomposed" sizes="57x57" href="../../../img/favicon/thinkib/apple-touch-icon-57x57-1.png"><link rel="apple-touch-icon-precomposed" sizes="114x114" href="../../../img/favicon/thinkib/apple-touch-icon-114x114-1.png"><link rel="apple-touch-icon-precomposed" sizes="72x72" href="../../../img/favicon/thinkib/apple-touch-icon-72x72-1.png"><link rel="apple-touch-icon-precomposed" sizes="144x144" href="../../../img/favicon/thinkib/apple-touch-icon-144x144-1.png"><link rel="apple-touch-icon-precomposed" sizes="60x60" href="../../../img/favicon/thinkib/apple-touch-icon-60x60-1.png"><link rel="apple-touch-icon-precomposed" sizes="120x120" href="../../../img/favicon/thinkib/apple-touch-icon-120x120-1.png"><link rel="apple-touch-icon-precomposed" sizes="76x76" href="../../../img/favicon/thinkib/apple-touch-icon-76x76-1.png"><link rel="apple-touch-icon-precomposed" sizes="152x152" href="../../../img/favicon/thinkib/apple-touch-icon-152x152-1.png"><link rel="icon" type="image/png" href="../../../img/favicon/thinkib/favicon-196x196-1.png" sizes="196x196"><link rel="icon" type="image/png" href="../../../img/favicon/thinkib/favicon-96x96-1.png" sizes="96x96"><link rel="icon" type="image/png" href="../../../img/favicon/thinkib/favicon-32x32-1.png" sizes="32x32"><link rel="icon" type="image/png" href="../../../img/favicon/thinkib/favicon-16x16-1.png" sizes="16x16"><link rel="icon" type="image/png" href="../../../img/favicon/thinkib/favicon-128-1.png" sizes="128x128"><meta name="application-name" content=" "><meta name="msapplication-TileColor" content="#FFFFFF"><meta name="msapplication-TileImage" content="https://www.thinkib.net/img/favicon/thinkib/mstile-144x144.png"><meta name="msapplication-square70x70logo" content="https://www.thinkib.net/img/favicon/thinkib/mstile-70x70.png"><meta name="msapplication-square150x150logo" content="https://www.thinkib.net/img/favicon/thinkib/mstile-150x150.png"><meta name="msapplication-wide310x150logo" content="https://www.thinkib.net/img/favicon/thinkib/mstile-310x150.png"><meta name="msapplication-square310x310logo" content="https://www.thinkib.net/img/favicon/thinkib/mstile-310x310.png">
</head>
<body onunload="" class="">
<!-- Google Tag Manager (noscript) -->
<noscript><iframe src="https://www.googletagmanager.com/ns.html?id=GTM-K5VSFSN" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>
<!-- End Google Tag Manager (noscript) -->
<div id="header">
<div class="wmap">
<div class="layout-wrapper">
<div class="container-fluid">
<div class="pull-right visible-phone">
<a href="https://www.inthinking.net">
<img class="header-logo" src="../../../img/header-logo-1.svg" style="height: 45px; width: auto;">
</a>
</div>
<div class="visible-phone" style="clear:both;"></div>
<div class="pull-left">
<h1><a href="/chemistry"><span style="">IBDP Chemistry brought to you by the IB Docs (2) Team</span></a></h1>
<p class="slogan hidden-phone"><span class="slogan"><em>InThinking</em> Subject Sites for teachers & their classes</span></p>
<p class="hidden-phone">Website by <strong>Geoffrey Neuss</strong></p>
<p class="hidden-phone">Updated 2 JIB Docs (2) Teamary 2023</p>
</div>
<div class="visible-phone" style="clear:both;"></div>
<div class="pull-right text-right header-right">
<a class="hidden-phone" href="https://www.inthinking.net">
<img class="header-logo" src="../../../img/header-logo-1.svg" style="height: 70px; width: auto;">
</a>
<div class="search">
<a href="#" class="toggle-menu-search" data-toggle="dropdown">
<i class="fa fa-2x fa-search"></i>
</a>
</div>
</div>
</div>
</div>
</div>
</div>
<div id="topmenu">
<div class="layout-wrapper">
<div>
<nav class="top-nav"><ul class="level-0"><li class=""><a href="../../../chemistry.html"><i class="fa fa-home"></i> Home</a><ul><li class=""><a href="/subscribe"><i class="fa fa-globe fixwidth"></i> Subscribe today</a></li><li class=""><a href="chemistry/sitemap"><i class="fa fa-sitemap fixwidth"></i> Sitemap</a></li><li class=""><a href="chemistry/last-updates"><i class="fa fa-file-text-o fixwidth"></i> Latest updates</a></li><li class=""><a href="chemistry/teaching-materials"><i class="fa fa-puzzle-piece fixwidth"></i> Teaching materials</a></li><li class=""><a href="chemistry/blog"><i class="fa fa-paperclip fixwidth"></i> Blog</a></li><li class=""><a href="chemistry/twitter"><i class="fa fa-twitter fixwidth"></i> Tweets</a></li><li><a><i class="fa fa-external-link fixwidth"></i> <em>InThinking</em> sites</a><ul><li><a class="text-right" href="https://thinkib.net"><span class="pull-left"> All subjects</span> <em style="opacity: .8;">www.thinkib.net</em></a></li><li><a href="https://www.thinkib.net/biology" target="_blank">IBDP Biology</a></li><li><a href="https://www.thinkib.net/businessmanagement" target="_blank">IBDP Business Management</a></li><li><a href="https://www.thinkib.net/economics" target="_blank">IBDP Economics</a></li><li><a href="https://www.thinkib.net/englishalit" target="_blank">IBDP English A Literature</a></li><li><a href="https://www.thinkib.net/englishalanglit" target="_blank">IBDP English A: Language & Literature</a></li><li><a href="https://www.thinkib.net/englishb" target="_blank">IBDP English B</a></li><li><a href="https://www.thinkib.net/ess" target="_blank">IBDP Environmental Systems & Societies</a></li><li><a href="https://www.thinkib.net/frenchb" target="_blank">IBDP French B</a></li><li><a href="https://www.thinkib.net/geography" target="_blank">IBDP Geography</a></li><li><a href="https://www.thinkib.net/german" target="_blank">IBDP German A: Language & Literature</a></li><li><a href="https://www.thinkib.net/history" target="_blank">IBDP History</a></li><li><a href="https://www.thinkib.net/mathanalysis" target="_blank">IBDP Maths: Analysis & Approaches</a></li><li><a href="https://www.thinkib.net/mathapplications" target="_blank">IBDP Maths: Applications & Interpretation</a></li><li><a href="https://www.thinkib.net/physics" target="_blank">IBDP Physics</a></li><li><a href="https://www.thinkib.net/psychology" target="_blank">IBDP Psychology</a></li><li><a href="https://www.thinkib.net/leadership" target="_blank">IB School Leadership</a></li><li><a href="https://www.thinkib.net/spanisha" target="_blank">IBDP Spanish A</a></li><li><a href="https://www.thinkib.net/spanish-abinitio" target="_blank">IBDP Spanish Ab Initio</a></li><li><a href="https://www.thinkib.net/spanishb" target="_blank">IBDP Spanish B</a></li><li><a href="https://www.thinkib.net/teachmaths" target="_blank">teachMathematics</a></li><li><a href="https://www.thinkib.net/visualarts" target="_blank">IBDP Visual Arts</a></li><li><a href="https://www.thinkib.net/myp-englishalanglit" target="_blank">IBMYP English Language & Literature</a></li><li><a href="https://www.thinkib.net/myp-resources" target="_blank">IBMYP Resources</a></li><li><a href="https://www.thinkib.net/myp-spanishb" target="_blank">IBMYP Spanish Language Acquisition</a></li><li><a href="https://www.thinkib.net/ibcp" target="_blank">IB Career-related Programme</a></li><li><a href="https://www.thinkigcse.net" target="_blank"><strong>ThinkIGCSE</strong> - <em>Subject sites for IGCSE teachers</em></a></li></ul></li></ul><li><li><a href="../16256/start-here-1.html">Start here</a><ul class="level-1"><li><a href="../36257/how-to-navigate-the-site-1.html">How to navigate the site</a></li><li><a href="../24826/using-student-access--1.html" class="father">Using student access </a><ul class="level-2"><li><a href="../27330/creating-student-accounts--1.html">Creating student accounts </a></li><li><a href="../32806/short-cut-to-give-students-access-to-a-page-1.html">Short cut to give students access to a page</a></li><li><a href="../27328/setting-assignments-1.html">Setting assignments</a></li><li><a href="../27351/managing-student-accounts-mark-book-1.html">Managing student accounts & mark book</a></li><li><a href="../27362/using-qbank-1.html">Using qBank</a></li></ul></li><li><a href="../16257/for-teachers-new-to-ib-chemistry-1.html" class="father">For teachers new to IB Chemistry</a><ul class="level-2"><li><a href="../16258/dart-board-chemistry-1.html">'Dart board' chemistry</a></li><li><a href="../16274/essential-resources-1.html">Essential resources</a></li><li><a href="../16276/syllabus-1.html">Syllabus</a></li><li><a href="../16278/possible-teaching-schedule-1.html">Possible teaching schedule</a></li></ul></li></ul></li><li><a href="../46318/teaching-learning-resources-1.html">Teaching, learning & resources</a><ul class="level-1"><li><a href="../17394/approaches-to-teaching-1.html" class="father">Approaches to teaching</a><ul class="level-2"><li><a href="../17395/teaching-styles--1.html">Teaching styles </a></li><li><a href="../17396/teaching-skills--1.html">Teaching skills </a></li><li><a href="../17398/workshops--1.html">Workshops </a></li><li><a href="../17397/teacher-recommendations--1.html">Teacher recommendations </a></li></ul></li><li><a href="../27280/approaches-to-learning-1.html" class="father">Approaches to learning</a><ul class="level-2"><li><a href="../27208/thinking-skills-1.html">Thinking skills</a></li><li><a href="../27216/reflection-1.html">Reflection</a></li><li><a href="../27209/communication-skills-1.html">Communication skills</a></li><li><a href="../27211/social-skills-1.html">Social skills</a></li><li><a href="../27232/self-management-1.html">Self-management</a></li><li><a href="../27312/research-1.html">Research</a></li></ul></li><li><a href="../17120/resources-1.html" class="father">Resources</a><ul class="level-2"><li><a href="../17119/ib-specific-books-1.html">IB specific books</a></li><li><a href="../17121/general-text-books-1.html">General text books</a></li><li><a href="../17131/post-ib-text-books-1.html">Post IB text books</a></li><li><a href="../17132/journals-1.html">Journals</a></li><li><a href="../17133/newspaper-articles-1.html">Newspaper articles</a></li><li><a href="../17124/demonstrations-1.html">Demonstrations</a></li><li><a href="../17139/chemistry-videos-1.html">Chemistry videos</a></li><li><a href="../17140/web-links-1.html">Web links</a></li><li><a href="../17138/chemistry-apps-1.html">Chemistry apps</a></li><li><a href="../17348/novel-uses-for-the-ib-data-booklet--1.html">Novel uses for the IB data booklet </a></li><li><a href="../17392/books-for-enjoyment--1.html">Books for enjoyment </a></li></ul></li><li><a href="../27313/unit-plans-1.html">Unit plans</a></li><li><a href="../22523/critical-thinking-1.html">Critical thinking</a></li><li><a href="../18044/do-you-speak-ib-1.html" class="father">Do you speak IB?</a><ul class="level-2"><li><a href="../17382/changes-to-terminology-1.html">Changes to terminology</a></li></ul></li><li><a href="../32761/school-closures-and-distance-learning-1.html">School closures and distance learning</a></li></ul></li><li><a href="../16347/core-ahl-1.html">Core & AHL</a><ul class="level-1"><li><a href="../16344/syllabus-1.html">Syllabus</a></li><li><a href="../16329/teaching-each-topic-sub-topic-1.html" class="father">Teaching each topic & sub-topic</a><ul class="level-2"><li><a href="../16328/topic-1-1.html">Topic 1</a></li><li><a href="../16907/topics-2-12--1.html">Topics 2 & 12 </a></li><li><a href="../17021/topics-3-13-1.html">Topics 3 & 13</a></li><li><a href="../17114/topics-4-14-1.html">Topics 4 & 14</a></li><li><a href="../17669/topics-5-15--1.html">Topics 5 & 15 </a></li><li><a href="../17848/topics-6-16-1.html">Topics 6 & 16</a></li><li><a href="../18038/topics-7-17--1.html">Topics 7 & 17 </a></li><li><a href="../18120/topics-8-18--1.html">Topics 8 & 18 </a></li><li><a href="../18350/topics-9-19-1.html">Topics 9 & 19</a></li><li><a href="../18475/topics-10-20--1.html">Topics 10 & 20 </a></li><li><a href="../17285/topics-11-21--1.html">Topics 11 & 21 </a></li></ul></li><li><a href="../16441/the-nature-of-science-1.html" class="father">The Nature of Science</a><ul class="level-2"><li><a href="../16450/key-terms-concepts-1.html">Key terms & concepts</a></li><li><a href="../34566/nos-critical-thinking-1.html">NOS & Critical Thinking</a></li><li><a href="../32100/how-the-elements-were-named-1.html">How the elements were named</a></li><li><a href="../36753/the-culture-of-chemistry-1.html">The Culture of Chemistry</a></li><li><a href="../17333/nature-of-science-questions-1.html">Nature of Science questions</a></li></ul></li><li><a href="../16413/incorporating-im-tok-utilization-etc-1.html" class="father">Incorporating IM, TOK, 'Utilization' etc.</a><ul class="level-2"><li><a href="../16414/topic-1-1.html">Topic 1</a></li><li><a href="../16916/topics-2-12-1.html">Topics 2 & 12</a></li><li><a href="../17023/topics-3-13--1.html">Topics 3 & 13 </a></li><li><a href="../17055/topics-4-14--1.html">Topics 4 & 14 </a></li><li><a href="../17270/topics-5-15--1.html">Topics 5 & 15 </a></li><li><a href="../17854/topics-6-16--1.html">Topics 6 & 16 </a></li><li><a href="../18041/topics-7-17--1.html">Topics 7 & 17 </a></li><li><a href="../18099/topics-8-18-1.html">Topics 8 & 18</a></li><li><a href="../18349/topics-9-19--1.html">Topics 9 & 19 </a></li><li><a href="../18420/topics-10-20-1.html">Topics 10 & 20</a></li><li><a href="../17269/topics-11-21--1.html">Topics 11 & 21 </a></li></ul></li><li><a href="../17866/utilization-relationships-between-topics--1.html" class="father">'Utilization' - Relationships between topics </a><ul class="level-2"><li><a href="../17867/relating-topics-4-14-to-all-the-other-topics-1.html">Relating Topics 4 & 14 to all the other topics</a></li><li><a href="../17868/example-of-connections-1.html">Example of connections</a></li><li><a href="../34404/hydroxychloroquine-ib-chemistry-1.html">Hydroxychloroquine & IB Chemistry</a></li><li><a href="../35418/ammonium-nitrate-ib-chemistry-1.html">Ammonium nitrate & IB Chemistry</a></li></ul></li><li><a href="../16685/multiple-choice-tests-for-each-topic-1.html" class="father">Multiple choice tests for each topic</a><ul class="level-2"><li><a href="../16687/sl-questions-by-topic-1.html">SL Questions by topic</a></li><li><a href="../16688/hl-questions-by-topic-1.html">HL Questions by topic</a></li></ul></li></ul></li><li><a href="../19044/options--1.html">Options </a><ul class="level-1"><li><a href="../19503/option-a--1.html" class="father">Option A </a><ul class="level-2"><li><a href="../19504/introduction-to-materials-science--1.html">Introduction to materials science </a></li><li><a href="../19519/metals-and-icp-spectroscopy-1.html">Metals and ICP spectroscopy</a></li><li><a href="../19541/catalysts--1.html">Catalysts </a></li><li><a href="../19580/liquid-crystals-1.html">Liquid crystals</a></li><li><a href="../19665/polymers--1.html">Polymers </a></li><li><a href="../19672/nanotechnology-1.html">Nanotechnology</a></li><li><a href="../19843/environmental-impact-plastics-1.html">Environmental impact - plastics</a></li><li><a href="../19858/superconducting-metals-x-ray-crystallography--1.html">Superconducting metals & X-ray crystallography </a></li><li><a href="../19666/condensation-polymers-1.html">Condensation polymers</a></li><li><a href="../19916/environmental-impact-heavy-metals-1.html">Environmental impact - heavy metals</a></li></ul></li><li><a href="../19284/option-b--1.html" class="father">Option B </a><ul class="level-2"><li><a href="../19290/introduction-to-biochemistry--1.html">Introduction to biochemistry </a></li><li><a href="../19287/proteins-enzymes--1.html">Proteins & enzymes </a></li><li><a href="../19291/lipids-1.html">Lipids</a></li><li><a href="../19299/carbohydrates--1.html">Carbohydrates </a></li><li><a href="../19305/vitamins--1.html">Vitamins </a></li><li><a href="../19313/biochemistry-the-environment--1.html">Biochemistry & the environment </a></li><li><a href="../19336/proteins-enzymes-ahl--1.html">Proteins & enzymes (AHL) </a></li><li><a href="../19347/nucleic-acids--1.html">Nucleic acids </a></li><li><a href="../19361/biological-pigments--1.html">Biological pigments </a></li><li><a href="../19366/stereochemistry-in-biomolecules-1.html">Stereochemistry in biomolecules</a></li></ul></li><li><a href="../19390/option-c--1.html" class="father">Option C </a><ul class="level-2"><li><a href="../19391/energy-sources-1.html">Energy sources</a></li><li><a href="../19407/fossil-fuels-1.html">Fossil fuels</a></li><li><a href="../19411/nuclear-fusion-nuclear-fission-reactions-1.html">Nuclear fusion & nuclear fission reactions</a></li><li><a href="../19429/solar-energy-1.html">Solar energy</a></li><li><a href="../19437/environmental-impact-global-warming-1.html">Environmental impact - global warming</a></li><li><a href="../19453/electrochemistry-rechargeable-batteries-fuel-cells-1.html">Electrochemistry, rechargeable batteries & fuel cells</a></li><li><a href="../19458/nuclear-fusion-fission-hl--1.html">Nuclear fusion & fission (HL) </a></li><li><a href="../19470/photovoltaic-cells-and-dsscs-1.html">Photovoltaic cells and DSSCs</a></li></ul></li><li><a href="../19078/option-d-1.html" class="father">Option D</a><ul class="level-2"><li><a href="../19079/pharmaceutical-products-drug-action--1.html">Pharmaceutical products & drug action </a></li><li><a href="../19158/aspirin-penicillin--1.html">Aspirin & penicillin </a></li><li><a href="../19174/opiates-1.html">Opiates</a></li><li><a href="../19184/ph-regulation-of-the-stomach-1.html">pH regulation of the stomach</a></li><li><a href="../19194/antiviral-medications--1.html">Antiviral medications </a></li><li><a href="../19211/environmental-impact-of-some-medications-1.html">Environmental impact of some medications</a></li><li><a href="../19254/taxol-a-chiral-auxiliary-case-study-1.html">Taxol - a chiral auxiliary case study</a></li><li><a href="../19258/nuclear-medicine--1.html">Nuclear medicine </a></li><li><a href="../19273/drug-detection-analysis--1.html">Drug detection & analysis </a></li></ul></li></ul></li><li><a href="../16592/practical-scheme-of-work-ia--1.html">Practical scheme of work & IA </a><ul class="level-1"><li><a href="../16682/internal-assessment-1.html" class="father">Internal Assessment</a><ul class="level-2"><li><a href="../18892/scaffolding-the-investigation-1.html">'Scaffolding' the investigation</a></li><li><a href="../18896/timing-organisation--1.html">Timing & organisation </a></li><li><a href="../18905/choosing-the-research-question-1.html">Choosing the research question</a></li><li><a href="../18946/personal-engagement-1.html">Personal engagement</a></li><li><a href="../18950/exploration-1.html">Exploration</a></li><li><a href="../18957/analysis-1.html">Analysis</a></li><li><a href="../18965/evaluation-1.html">Evaluation</a></li><li><a href="../18966/communication-1.html">Communication</a></li><li><a href="../19882/internal-standardization-of-the-ia-1.html">Internal standardization of the IA</a></li><li><a href="../19901/submitting-the-samples-for-moderation-2.html">Submitting the samples for moderation</a></li><li><a href="../33754/ten-suggestions-for-ias-using-secondary-data-1.html">Ten suggestions for IAs using secondary data</a></li><li><a href="../37544/gaining-full-marks-for-a-databased-ia--1.html">Gaining full marks for a databased IA </a></li><li><a href="../19506/ia-example-marking-exercise--1.html">IA example & marking exercise </a></li><li><a href="../23929/genuine-examples-of-moderated-ia-reports-1.html">Genuine examples of moderated IA reports</a></li><li><a href="../25234/examples-of-teacher-marked-ia-reports--1.html">Examples of teacher-marked IA reports </a></li><li><a href="../37542/history-of-internal-assessment-1.html">History of Internal Assessment</a></li></ul></li><li><a href="../16598/mandatory-laboratory-components-1.html" class="father">Mandatory laboratory components</a><ul class="level-2"><li><a href="../16613/formula-of-magnesium-oxide--1.html">Formula of magnesium oxide </a></li><li><a href="../16612/determining-the-mr-of-an-unknown-gas-1.html">Determining the <i>M</i><sub>r</sub> of an unknown gas</a></li><li><a href="../16615/acid-base-titrations--1.html">Acid-base titrations </a></li><li><a href="../16616/a-green-acid-base-practical-1.html">A green acid-base practical</a></li><li><a href="../16617/analysis-of-aspirin-tablets-1.html">Analysis of aspirin tablets</a></li><li><a href="../16618/caco3-in-egg-shells-1.html">CaCO<sub>3</sub> in egg shells</a></li><li><a href="../16644/enthalpy-changes-1.html">Enthalpy changes</a></li><li><a href="../16631/reaction-rates-1.html">Reaction rates</a></li><li><a href="../16635/rate-dependent-factors-1.html">Rate-dependent factors</a></li><li><a href="../16636/determining-ea-for-a-reaction-1.html">Determining <i>E</i><sub>a</sub> for a reaction</a></li><li><a href="../16637/iodination-of-propanone-1.html">Iodination of propanone</a></li><li><a href="../18144/titrations-with-a-ph-meter-1.html">Titrations with a pH meter</a></li><li><a href="../18355/redox-titration-with-kmno4--1.html">Redox titration with KMnO<sub>4</sub> </a></li><li><a href="../16640/voltaic-cells-1.html">Voltaic cells</a></li><li><a href="../16659/3-d-molecular-modelling--1.html">3-D molecular modelling </a></li></ul></li><li><a href="../17168/other-good-practicals-1.html" class="father">Other good practicals</a><ul class="level-2"><li><a href="../17196/common-chemical-reactions-1.html">Common chemical reactions</a></li><li><a href="../227/elements-oxides-of-the-third-period--1.html">Elements & oxides of the third period </a></li><li><a href="../17239/the-halogens-1.html">The halogens</a></li><li><a href="../17162/boiling-points-of-mixtures-1.html">Boiling points of mixtures</a></li><li><a href="../17170/polarity-of-molecules-1.html">Polarity of molecules</a></li><li><a href="../18083/le-chateliers-principle--1.html">Le Chatelier's principle </a></li><li><a href="../19582/determining-kc-for-an-esterification-reaction-1.html">Determining <i>K</i><sub>c</sub> for an esterification reaction</a></li><li><a href="../18164/redox-reactions-of-vanadium--1.html">Redox reactions of vanadium </a></li><li><a href="../18351/chlorine-in-swimming-pools--1.html">Chlorine in swimming pools </a></li><li><a href="../18178/analysis-of-cuii-ions-in-solution--1.html">Analysis of Cu(II) ions in solution </a></li><li><a href="../18179/percentage-of-copper-in-brass-1.html">Percentage of copper in brass</a></li><li><a href="../18356/electrolytic-cells--1.html">Electrolytic cells </a></li><li><a href="../18598/reactions-of-organic-compounds-1.html">Reactions of organic compounds</a></li><li><a href="../18752/hydrolysis-of-halogenoalkanes-1.html">Hydrolysis of halogenoalkanes</a></li><li><a href="../18784/preparation-of-13-dinitrobenzene--1.html">Preparation of 1,3-dinitrobenzene </a></li><li><a href="../19022/determination-of-an-organic-structure-1.html">Determination of an organic structure</a></li><li><a href="../19887/preparation-of-nylon-66-1.html">Preparation of nylon 6,6</a></li><li><a href="../19343/determination-of-vitamin-c-content--1.html">Determination of vitamin C content </a></li><li><a href="../19342/hydrolysis-of-starch--1.html">Hydrolysis of starch </a></li><li><a href="../19159/preparation-purification-of-aspirin--1.html">Preparation & purification of aspirin </a></li></ul></li><li><a href="../18851/ict-in-practical-work-1.html" class="father">ICT in practical work</a><ul class="level-2"><li><a href="../18852/data-logging--1.html">Data logging </a></li><li><a href="../18853/software-for-graph-plotting--1.html">Software for graph plotting </a></li><li><a href="../18854/spreadsheets-for-data-processing--1.html">Spreadsheets for data processing </a></li><li><a href="../18855/databases-1.html">Databases</a></li><li><a href="../18856/computer-modelling-simulations--1.html">Computer modelling & simulations </a></li></ul></li><li><a href="../16594/group-4-project-1.html" class="father">Group 4 Project</a><ul class="level-2"><li><a href="../16595/practicalities-1.html">Practicalities</a></li><li><a href="../16596/reflective-statement--2.html">Reflective statement </a></li></ul></li><li><a href="../16666/a-new-laboratory-1.html">A new laboratory?</a></li></ul></li><li class="selected"><a href="../16284/exams-1.html">Exams</a><ul class="level-1"><li><a href="../16286/essential-facts-1.html" class="father">Essential Facts</a><ul class="level-2"><li><a href="../16287/objectives-command-terms-1.html">Objectives & command terms</a></li><li><a href="../16288/grade-descriptors-1.html">Grade descriptors</a></li><li><a href="../16289/grade-boundaries-1.html">Grade boundaries</a></li></ul></li><li><a href="../16302/paper-1-multiple-choice-1.html" class="father">Paper 1 (Multiple Choice)</a><ul class="level-2"><li><a href="../16303/advice-to-students-paper-1-1.html">Advice to students (Paper 1)</a></li><li><a href="../31515/practice-paper-1-exams-1.html">Practice Paper 1 exams</a></li></ul></li><li class="selected"><a href="../16305/paper-2-1.html" class="father">Paper 2</a><ul class="level-2"><li><a href="../16306/advice-to-students-paper-2-1.html">Advice to students (Paper 2)</a></li><li class="selected"><a href="../16307/areas-of-difficulty-1.html">Areas of difficulty</a></li></ul></li><li><a href="../16313/paper-3--1.html" class="father">Paper 3 </a><ul class="level-2"><li><a href="../16314/advice-to-students-paper-3-1.html">Advice to students (Paper 3)</a></li><li><a href="../16342/data-response-questions-1.html">Data response questions</a></li><li><a href="../20054/experimental-work-questions-1.html">Experimental work questions</a></li></ul></li><li><a href="../16324/the-examination-process-1.html" class="father">The examination process</a><ul class="level-2"><li><a href="../16316/setting-the-exam-papers-1.html">Setting the exam papers</a></li><li><a href="../16317/predicted-grades-1.html">Predicted grades</a></li><li><a href="../16318/marking-the-papers-1.html">Marking the papers</a></li><li><a href="../16319/commenting-on-the-exams-1.html">Commenting on the exams</a></li><li><a href="../16320/grade-awarding-1.html">Grade Awarding</a></li><li><a href="../16321/enquiry-upon-results-1.html">Enquiry upon results</a></li><li><a href="../16322/chief-examiners-report-1.html">Chief Examiner's report</a></li><li><a href="../16323/retaking-the-exam-1.html">Retaking the exam</a></li></ul></li><li><a href="../16325/faqs-1.html">FAQs</a></li></ul></li><li><a href="../3147/ib-core-1.html">IB Core</a><ul class="level-1"><li><a href="../3149/learner-profile-1.html">Learner Profile</a></li><li><a href="../21735/extended-essays--1.html" class="father">Extended Essays </a><ul class="level-2"><li><a href="../21736/overview--1.html">Overview </a></li><li><a href="../21780/responsibilities-1.html">Responsibilities</a></li><li><a href="../21790/resources-1.html">Resources</a></li><li><a href="../21800/research-1.html">Research</a></li><li><a href="../21804/writing-the-essay-1.html">Writing the essay</a></li><li><a href="../21810/assessment-1.html">Assessment</a></li><li><a href="../22434/summary-of-advice--1.html">Summary of advice </a></li><li><a href="../25272/faqs--1.html">FAQs </a></li></ul></li><li><a href="../307/theory-of-knowledge-tok-1.html" class="father">Theory of Knowledge (TOK)</a><ul class="level-2"><li><a href="../41171/the-12-tok-concepts-1.html">The 12 TOK concepts</a></li><li><a href="../3507/why-tok-chemistry-1.html">Why TOK & Chemistry?</a></li><li><a href="../3505/a-modern-paradigm-1.html">A modern paradigm</a></li></ul></li></ul></li><li><a href="../17783/fast-track-to-tests-questions-1.html">Fast track to tests & questions</a><ul class="level-1"><li><a href="../17784/sl-multiple-choice-tests-on-individual-topics-1.html">SL Multiple choice tests on individual topics</a></li><li><a href="../24351/sl-multiple-choice-quizzes-on-sub-topics-1.html">SL Multiple choice 'quizzes' on sub-topics</a></li><li><a href="../31519/sl-practice-paper-1-exams-1.html">SL Practice Paper 1 exams</a></li><li><a href="../17786/sl-questions-on-each-sub-topic-1.html">SL Questions on each sub-topic</a></li><li><a href="../20431/sl-paper-3-section-a-questions-1.html">SL Paper 3 Section A questions</a></li><li><a href="../17792/sl-questions-on-the-options-1.html">SL Questions on the options</a></li><li><a href="../24897/sl-quizzes-on-option-sub-topics--1.html">SL Quizzes on option sub-topics </a></li><li><a href="../17785/hl-multiple-choice-tests-on-individual-topics-1.html">HL Multiple choice tests on individual topics</a></li><li><a href="../24352/hl-multiple-choice-quizzes-on-sub-topics-1.html">HL Multiple choice 'quizzes' on sub-topics</a></li><li><a href="../31520/hl-practice-paper-1-exams--1.html">HL Practice Paper 1 exams </a></li><li><a href="../17787/hl-questions-on-each-sub-topic--1.html">HL Questions on each sub-topic </a></li><li><a href="../20428/hl-paper-3-section-a-questions-1.html">HL Paper 3 Section A questions</a></li><li><a href="../17793/hl-questions-on-the-options-1.html">HL Questions on the options</a></li><li><a href="../24973/hl-quizzes-on-option-sub-topics-1.html">HL Quizzes on option sub-topics</a></li><li><a href="../41573/printable-versions-of-written-tasks--1.html">Printable versions of written tasks </a></li></ul></li><li><a href="../41465/complete-course-for-students--2.html">Complete course for students </a><ul class="level-1"><li><a href="../27988/full-coverage-of-each-topic-and-sub-topic-2.html" class="father">Full coverage of each topic and sub-topic</a><ul class="level-2"><li><a href="../27959/topic-1-stoichiometric-relationships-1.html">Topic 1 : Stoichiometric relationships</a></li><li><a href="../27960/topics-2-12-atomic-structure-1.html">Topics 2 & 12 : Atomic structure</a></li><li><a href="../27965/topics-3-13-periodicity-1.html">Topics 3 & 13 : Periodicity</a></li><li><a href="../27971/topics-4-14-chemical-bonding-structure-1.html">Topics 4 & 14 : Chemical bonding & structure</a></li><li><a href="../27987/topics-5-15-energeticsthermochemistry-1.html">Topics 5 & 15 : Energetics/thermochemistry</a></li><li><a href="../27995/topics-6-16-chemical-kinetics-1.html">Topics 6 & 16 : Chemical kinetics</a></li><li><a href="../28001/topics-7-17-equilibrium--1.html">Topics 7 & 17 : Equilibrium </a></li><li><a href="../28017/topics-8-18-acids-and-bases--1.html">Topics 8 & 18 : Acids and bases </a></li><li><a href="../28031/topics-9-19-redox-process-1.html">Topics 9 & 19 : Redox process</a></li><li><a href="../28061/topics-10-20-organic-chemistry-1.html">Topics 10 & 20 : Organic chemistry</a></li><li><a href="../28038/topics-11-21-measurement-data-processing-analysis-1.html">Topics 11 & 21 : Measurement, data processing & analysis</a></li><li><a href="../28074/option-a-materials--1.html">Option A : Materials </a></li><li><a href="../28087/option-b-biochemistry-1.html">Option B : Biochemistry</a></li><li><a href="../28098/option-c-energy--1.html">Option C : Energy </a></li><li><a href="../28109/option-d-medicinal-chemistry-1.html">Option D : Medicinal chemistry</a></li></ul></li><li><a href="../41553/practical-work-including-ia-group-4-project--1.html" class="father">Practical work (including IA & Group 4 Project) </a><ul class="level-2"><li><a href="../41528/internal-assessment-1.html">Internal Assessment</a></li><li><a href="../41657/group-4-project-1.html">Group 4 Project</a></li></ul></li><li><a href="../41387/approaches-to-learning--1.html" class="father">Approaches to learning </a><ul class="level-2"><li><a href="../41380/thinking-skills-1.html">Thinking skills</a></li><li><a href="../41383/communication-skills-1.html">Communication skills</a></li><li><a href="../41384/social-skills--1.html">Social skills </a></li><li><a href="../41385/self-management-skills-1.html">Self-management skills</a></li><li><a href="../41386/research-skills-1.html">Research skills</a></li><li><a href="../41382/reflection-skills--1.html">Reflection skills </a></li></ul></li><li><a href="../41488/the-nature-of-science-1.html" class="father">The Nature of Science</a><ul class="level-2"><li><a href="../41489/key-terms-concepts--1.html">Key terms & concepts </a></li><li><a href="../41492/how-the-elements-were-named--1.html">How the elements were named </a></li><li><a href="../41490/nos-critical-thinking-1.html">NOS & Critical Thinking</a></li><li><a href="../41493/the-culture-of-chemistry--1.html">The Culture of Chemistry </a></li><li><a href="../41494/nature-of-science-questions--1.html">Nature of Science questions </a></li></ul></li><li><a href="../41401/external-assessment-exams-1.html" class="father">External assessment (Exams)</a><ul class="level-2"><li><a href="../41403/essential-facts--1.html">Essential Facts </a></li><li><a href="../41409/paper-1-multiple-choice--1.html">Paper 1 (Multiple Choice) </a></li><li><a href="../41417/paper-2--1.html">Paper 2 </a></li><li><a href="../41431/paper-3--1.html">Paper 3 </a></li></ul></li><li><a href="../41662/extended-essay--1.html" class="father">Extended Essay </a><ul class="level-2"><li><a href="../41685/preparation-1.html">Preparation</a></li><li><a href="../41686/researching--1.html">Researching </a></li><li><a href="../42075/writing-the-essay-1.html">Writing the essay</a></li><li><a href="../41687/assessment-1.html">Assessment</a></li></ul></li></ul></li></ul></nav>
</div>
</div>
</div>
<nav id="nav-menu-search" style="display: none;">
<div class="layout-wrapper">
<form class="form-inline" role="search" method="get" action="chemistry/search">
<input id="nav-search" name="s" type="search" placeholder="Search Chemistry..." value="">
<button class="btn btn-sm btn-primary" type="submit">
Search
</button>
<a href="#" class="toggle-menu-search" title="Close">
<i class="fa fa-lg fa-times gray"></i>
</a>
</form>
</div>
</nav>
<div class="layout-wrapper">
<div id="container" class="container-fluid">
<div id="content">
<div class="row-fluid">
<div id="left-column" class="span3"><div class="dropdown" id="userbox"><a class="dropdown-toggle btn" data-toggle="dropdown" onclick="return false;"><img src="../../../img/user/t/IBRR.jpg" style="width: 16px; height: 16px; margin: -2px 0 0 0;"> IB Docs (2) Team <i class="fa fa-caret-down gray"></i></a><ul class="dropdown-menu" style="min-width: 200px"><li><a href="https://www.thinkib.net/chemistry" class="" title=""><i class="fa fa-globe fixwidth colored"></i>IBDP Chemistry</a></li><li class="divider"></li><li><a href="https://www.thinkib.net/chemistry/user" class="" title="Check & modify your profile"><i class="fa fa-user fixwidth colored"></i>My profile</a></li><li><a href="https://www.thinkib.net/chemistry/sitemap" class="" title="Get an overview of the site"><i class="fa fa-sitemap colored fixwidth colored"></i>Sitemap</a></li><li><a href="chemistry/std-access" class="" title="Set up/Manage student access"><i class="fa fa-group fixwidth colored"></i>Student access</a></li><li><a href="https://www.thinkib.net/chemistry/user/teacher-accounts" class="" title="Manage teacher accounts"><i class="fa fa-cogs fixwidth colored"></i>Teacher accounts</a></li><li><a href="https://www.thinkib.net/chemistry/user/bookmarks" class="" title="Manage your bookmarked pages"><i class="fa fa-star fixwidth colored"></i>My favorites</a></li><li><a href="https://www.thinkib.net/chemistry/user/messages" class="" title="Read your messages"><i class="fa fa-envelope-o fixwidth colored"></i>Messages</a></li><li><a href="/help/thinkib" class="pop-up-help" title="Help"><i class="fa fa-info-circle fixwidth colored"></i>Help</a></li><li><a href="https://www.thinkib.net/subscribe/" class="" title="Add / Renew subjects"><i class="fa fa-refresh fixwidth colored"></i>Renew</a></li><li class="divider"></li><li><a href="chemistry?logout=1"><i class="fa fa-power-off fixwidth colored"></i>Log out</a></li></ul></div><div id="std-teacher-only" style="padding-bottom: 10px;"><div style="display:flex;align-items:center"><img src="../../../img/icons/teacher.svg" style="margin: 0px;width:32px;height:auto;"><span style="color: #224466; font-weight: bold; margin-left: 5px;">Teacher only page</span></div></div><nav id="sidemenu" class="side-nav"><div class="header"><span style="color: #fff;"><a href="../16284/exams-1.html">Exams</a></span><span id="sidetreecontrol"><a title="Collapse all" rel="collapse" href="#"><i class="fa fa-minus-circle"></i></a> <a title="Expand all" rel="expand" href="#"><i class="fa fa-plus-circle"></i></a></span></div><ul class="level-0 always-expanded"><li class=" parent" style="padding-left: 0px"><i class="expander fa fa-caret-right "></i><a href="../16286/essential-facts-1.html" title="Essential Facts">Essential Facts</a></li><ul class="level-1 "><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16287/objectives-command-terms-1.html" title="Objectives & command terms">Objectives & command terms</a></li><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16288/grade-descriptors-1.html" title="Grade descriptors">Grade descriptors</a></li><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16289/grade-boundaries-1.html" title="Grade boundaries">Grade boundaries</a></li></ul><li class=" parent" style="padding-left: 0px"><i class="expander fa fa-caret-right "></i><a href="../16302/paper-1-multiple-choice-1.html" title="Paper 1 (Multiple Choice)">Paper 1 (Multiple Choice)</a></li><ul class="level-1 "><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16303/advice-to-students-paper-1-1.html" title="Advice to students (Paper 1)">Advice to students (Paper 1)</a></li><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../31515/practice-paper-1-exams-1.html" title="Practice Paper 1 exams">Practice Paper 1 exams</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../31516/sl-practice-paper-1-1.html" title="SL Practice Paper 1 (1)">SL Practice Paper 1 (1)</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../31677/sl-practice-paper-1-2-.html" title="SL Practice Paper 1 (2) ">SL Practice Paper 1 (2) </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../31806/sl-practice-paper-1-3-.html" title="SL Practice Paper 1 (3) ">SL Practice Paper 1 (3) </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../31518/hl-practice-paper-1-1-.html" title="HL Practice Paper 1 (1) ">HL Practice Paper 1 (1) </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../31696/hl-practice-paper-1-2-.html" title="HL Practice Paper 1 (2) ">HL Practice Paper 1 (2) </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../32111/hl-practice-paper-1-3-.html" title="HL Practice Paper 1 (3) ">HL Practice Paper 1 (3) </a></li></ul></ul><li class="ancestor parent" style="padding-left: 0px"><i class="expander fa fa-caret-right fa-rotate-90"></i><a href="../16305/paper-2-1.html" title="Paper 2">Paper 2</a></li><ul class="level-1 expanded"><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16306/advice-to-students-paper-2-1.html" title="Advice to students (Paper 2)">Advice to students (Paper 2)</a></li><li class="ancestor parent" style="padding-left: 14px"><i class="expander fa fa-caret-right fa-rotate-90"></i><a href="../16307/areas-of-difficulty-1.html" title="Areas of difficulty">Areas of difficulty</a></li><ul class="level-2 expanded"><li class="current" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="misuse-of-formulas.html" title="Misuse of formulas">Misuse of formulas</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../16309/ie-graphs.html" title="IE graph(s)">IE graph(s)</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../16311/vsepr.html" title="VSEPR">VSEPR</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../31240/understanding-and-using-g-.html" title="Understanding and using ΔG ">Understanding and using Δ<em>G </em></a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../32566/manipulating-equilibrium-constants-.html" title="Manipulating equilibrium constants ">Manipulating equilibrium constants </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../31229/understanding-the-activity-series.html" title="Understanding the activity series">Understanding the activity series</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../16310/using-electrode-potentials.html" title="Using electrode potentials">Using electrode potentials</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../16308/curly-arrows.html" title="'Curly arrows'">'Curly arrows'</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../33687/understanding-hybridization.html" title="Understanding hybridization">Understanding hybridization</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../32529/factors-affecting-the-rate-of-nucleophilic-substitution-reaction.html" title="Factors affecting the rate of nucleophilic substitution reactions">Factors affecting the rate of nucleophilic substitution reactions</a></li></ul></ul><li class=" parent" style="padding-left: 0px"><i class="expander fa fa-caret-right "></i><a href="../16313/paper-3--1.html" title="Paper 3 ">Paper 3 </a></li><ul class="level-1 "><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16314/advice-to-students-paper-3-1.html" title="Advice to students (Paper 3)">Advice to students (Paper 3)</a></li><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16342/data-response-questions-1.html" title="Data response questions">Data response questions</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../16339/data-response-example-1.html" title="Data response Example 1">Data response Example 1</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../16340/data-response-example-2.html" title="Data response Example 2">Data response Example 2</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../16341/data-response-example-3.html" title="Data response Example 3">Data response Example 3</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../17292/data-response-example-4.html" title="Data response Example 4">Data response Example 4</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20333/data-response-example-5.html" title="Data response Example 5">Data response Example 5</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20334/data-response-example-6-.html" title="Data response Example 6 ">Data response Example 6 </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20367/data-response-example-7-.html" title="Data response Example 7 ">Data response Example 7 </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20381/data-response-example-8-.html" title="Data response Example 8 ">Data response Example 8 </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20461/data-response-example-9-.html" title="Data response Example 9 ">Data response Example 9 </a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../20054/experimental-work-questions-1.html" title="Experimental work questions">Experimental work questions</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20033/experimental-work-question-1.html" title="Experimental work Question 1">Experimental work Question 1</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20034/experimental-work-question-2.html" title="Experimental work Question 2">Experimental work Question 2</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20042/experimental-work-question-3.html" title="Experimental work Question 3">Experimental work Question 3</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20065/experimental-work-question-4.html" title="Experimental work Question 4">Experimental work Question 4</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20073/experimental-work-question-5.html" title="Experimental work Question 5">Experimental work Question 5</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20070/experimental-work-question-6.html" title="Experimental work Question 6">Experimental work Question 6</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20076/experimental-work-question-7.html" title="Experimental work Question 7">Experimental work Question 7</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20064/experimental-work-question-8.html" title="Experimental work Question 8">Experimental work Question 8</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../20056/experimental-work-question-9.html" title="Experimental work Question 9">Experimental work Question 9</a></li></ul></ul><li class=" parent" style="padding-left: 0px"><i class="expander fa fa-caret-right "></i><a href="../16324/the-examination-process-1.html" title="The examination process">The examination process</a></li><ul class="level-1 "><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16316/setting-the-exam-papers-1.html" title="Setting the exam papers">Setting the exam papers</a></li><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16317/predicted-grades-1.html" title="Predicted grades">Predicted grades</a></li><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16318/marking-the-papers-1.html" title="Marking the papers">Marking the papers</a></li><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16319/commenting-on-the-exams-1.html" title="Commenting on the exams">Commenting on the exams</a></li><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16320/grade-awarding-1.html" title="Grade Awarding">Grade Awarding</a></li><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16321/enquiry-upon-results-1.html" title="Enquiry upon results">Enquiry upon results</a></li><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16322/chief-examiners-report-1.html" title="Chief Examiner's report">Chief Examiner's report</a></li><li class="" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../16323/retaking-the-exam-1.html" title="Retaking the exam">Retaking the exam</a></li></ul><li class="" style="padding-left: 0px"><i class="expander fa fa-caret-right "></i><a href="../16325/faqs-1.html" title="FAQs">FAQs</a></li></ul></nav></div><!-- /#left-column-->
<div id="main-column" class="span9"><article id="main-article"><a id="exit-fs" title="Exit presentation mode" href="#" onclick="return false;"><i class="fa fa-arrows-alt"></i></a><ul class="page-actions no-print stacked nav nav-list visible-desktop"><li><a class="presentation" href="#" onclick="return false;"><i class="fa fa-desktop"></i><span>Presentation mode</span></a></li><li><a class="print-section-blog" href="#" onclick="return false;"><i class="fa fa-print"></i><span>Print this page</span></a></li><li><a class="page-bookmarker stacked" data-ticket="IB Docs (2) Team" data-pid="32586" href="#" onclick="return false;"><i class="fa fa-star"></i><span>Favourite</span></a><textarea data-ticket="IB Docs (2) Team" data-pid="32586" id="editor" class="favcomms hidden" placeholder="Your personal notes..."></textarea></li><li><a class="personal-notes" href="#" onclick="return false;"><i class="fa fa-file-text"></i><span>Personal notes</span></a></li><li><a class="" data-toggle="modal" href="#modal-feedback" onclick="return false;"><i class="fa fa-envelope-o"></i><span>Feedback</span></a></li><li class="dropdown"><a class="dropdown-toggle" data-toggle="dropdown" data-target="#" href="#"><i class="fa fa-share-alt"></i><span>Share this page</span></a><ul class="dropdown-menu" role="menu"><li><a class="" target="_blank" title="Share on Twitter" href="https://twitter.com/share?text=%22Misuse+of+formulas%22+-+via+%40InThinker+%23chemistry%0A&url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas"><i class="fa fa-twitter-square"></i><span>Twitter</span></a></li><li><a class="" target="_blank" title="Share on Facebook" href="https://www.facebook.com/sharer.php?u=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas&t=Misuse+of+formulas"><i class="fa fa-facebook-square"></i><span>Facebook</span></a></li><li><a class="" href="http://www.linkedin.com/shareArticle?mini=true&url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas"><i class="fa fa-linkedin-square"></i><span>LinkedIn</span></a></li><li><a class="" href="https://plus.google.com/share?url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas"><i class="fa fa-google-plus-square"></i><span>Google +</span></a></li><li><a class="" href="mailto:?subject=Misuse of formulas&body=Students often use mathematical formulas to solve chemical problems in exams and sometimes arrive at the wrong answer. This page looks at why this is so and encourages students to work always from first principles rather...%0Ahttps%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas"><i class="fa fa-envelope"></i><span>Email</span></a></li></ul></li><li><a class="" href="chemistry/teaching-materials"><i class="fa fa-puzzle-piece colored"></i><span>Teaching materials</span></a></li></ul><div class="page-actions no-print navbar inline hidden-desktop"><div class="navbar-inner"><ul class="nav"><li><a class="presentation" href="#" onclick="return false;"><i class="fa fa-desktop"></i></a></li><li><a class="print-section-blog" href="#" onclick="return false;"><i class="fa fa-print"></i></a></li><li><a class="page-bookmarker" data-ticket="IB Docs (2) Team" data-pid="32586" href="#" onclick="return false;"><i class="fa fa-star"></i></a></li><li><a class="personal-notes" href="#" onclick="return false;"><i class="fa fa-file-text"></i></a></li><li><a class="" data-toggle="modal" href="#modal-feedback" onclick="return false;"><i class="fa fa-envelope-o"></i></a></li><li class="dropdown"><a class="dropdown-toggle" data-toggle="dropdown" data-target="#" href="#"><i class="fa fa-share-alt"></i></a><ul class="dropdown-menu" role="menu"><li><a class="" target="_blank" title="Share on Twitter" href="https://twitter.com/share?text=%22Misuse+of+formulas%22+-+via+%40InThinker+%23chemistry%0A&url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas"><i class="fa fa-twitter-square"></i><span>Twitter</span></a></li><li><a class="" target="_blank" title="Share on Facebook" href="https://www.facebook.com/sharer.php?u=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas&t=Misuse+of+formulas"><i class="fa fa-facebook-square"></i><span>Facebook</span></a></li><li><a class="" href="http://www.linkedin.com/shareArticle?mini=true&url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas"><i class="fa fa-linkedin-square"></i><span>LinkedIn</span></a></li><li><a class="" href="https://plus.google.com/share?url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas"><i class="fa fa-google-plus-square"></i><span>Google +</span></a></li><li><a class="" href="mailto:?subject=Misuse of formulas&body=Students often use mathematical formulas to solve chemical problems in exams and sometimes arrive at the wrong answer. This page looks at why this is so and encourages students to work always from first principles rather...%0Ahttps%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas"><i class="fa fa-envelope"></i><span>Email</span></a></li></ul></li><li><a class="" href="chemistry/teaching-materials"><i class="fa fa-puzzle-piece colored"></i></a></li></ul></div></div><h1 class="section-title">Misuse of formulas</h1><ul class="breadcrumb"><li><a title="Home" href="https://www.thinkib.net/chemistry"><i class="fa fa-home"></i></a><span class="divider"><i class="fa fa-chevron-right"></i></span></li><li><a title="Go to: Exams" href="../16284/exams-1.html">Exams</a><span class="divider"><i class="fa fa-chevron-right"></i></span></li><li><a title="Go to: Paper 2" href="../16305/paper-2-1.html">Paper 2</a><span class="divider"><i class="fa fa-chevron-right"></i></span></li><li><a title="Go to: Areas of difficulty" href="../16307/areas-of-difficulty-1.html">Areas of difficulty</a><span class="divider"><i class="fa fa-chevron-right"></i></span></li><li><span>Misuse of formulas</span></li></ul><div id="std-sidebox-task-added-msg"></div><div id="modal-feedback" class="modal hide fade text-left" tabindex="-1" role="dialog" aria-labelledby="log-in form" aria-hidden="true">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>
<h3>Misuse of formulas: Feedback</h3>
</div>
<div class="modal-body">
<form method="post" id="feedback-form">
<div class="row-fluid">
<div class="span12" style="margin: 12px 0">
<p>
Which of the following best describes your feedback?
</p>
<label class="radio" style="float: left; margin-right: 12px">
<input type="radio" checked="checked" value="useful" name="feedback-type">
Recommend
</label><label class="radio" style="float: left; margin-right: 12px">
<input type="radio" value="error" name="feedback-type">
Report a problem
</label><label class="radio" style="float: left; margin-right: 12px">
<input type="radio" value="improve" name="feedback-type">
Suggest an improvement
</label><label class="radio" style="float: left; margin-right: 12px">
<input type="radio" value="other" name="feedback-type">
Other
</label>
</div>
</div>
<div class="row-fluid">
<label>Comments:</label>
<div class="row-fluid">
<textarea class="span12" name="feedback-comment" placeholder="Your feedback... (optional)"></textarea>
</div>
</div>
<input type="hidden" name="feedback-submited" value="1">
</form>
</div>
<div class="modal-footer">
<button class="btn btn-large" type="button" data-dismiss="modal" aria-hidden="true">
<i class="fa fa-remove"></i>
Cancel
</button>
<button class="btn pull-right" id="submit-feedback" onclick="javascript:$('#feedback-form').submit();return false;">
<i class="fa fa-check"></i>
Submit
</button>
</div>
</div><section id="main-content"><div id="toc-1672972255" class="toc"><a href="#" class="toc-switcher" title="Show table of contents"><small><i class="fa fa-reorder"></i> Table of contents <span class="pull-right"><i class="fa fa-chevron-down"></i></span></small></a></div><p>Students often use mathematical formulas to solve chemical problems in exams and sometimes arrive at the wrong answer. This page looks at why this is so and encourages students to work always from first principles rather than mindlessly 'plug' values into a formula that they are unable to derive for themselves. It gives worked examples and provides some further practice questions with worked answers.</p><p style="text-align: center;"><img alt="" class="noborder" src="../../../ib/chemistry/images/2014%20Exams/m1v1%3Dm2v2.png" style="width: 234px; height: 88px;"></p><div class="blueBg"><h1>Introduction</h1><p>Both mathematics and science make much use of formulas to solve problems. There is nothing inherently wrong in using a formula. In fact in many cases it can save a considerable amount of time. For example, Einstein is reputed to have said that compound interest is the eighth wonder of the world – “He who understands it earns it… he who doesn’t… pays it.”. A person who 30 years ago put $1000 dollars in an investment account that paid 7% interest per year ($0.07 per dollar) would have gained 30 x $70 in interest if the interest had been withdrawn at the end of each year giving a total sum of $3100 if the original investment is also included. However if the interest had been left in the account the formula A = P (1 + r)<sup>t</sup> (where A = the future value, P = the principal investment amount, r = the interest rate and t = time) shows that the $1000 initial investment would have grown to $7612 after 30 years. If it had been left for 50 years the figures would have been $4500 and $29460 respectively. Clearly using this particular formula saves all the tedious work of working out the increase and compounding it for each year etc.</p><hr class="hidden"><p>Unfortunately some chemistry students who make considerable use of formulas in exams often arrive at the wrong answer because they have either misused a formula or have been unable to apply the correct formula to solve the problem.</p><hr class="hidden"><p>There are several reasons why this may be so.</p><hr class="hidden"></div><hr class="hidden"><div class="yellowBg"><h1>Reasons for errors using formulas</h1><h4>1. The formula is remembered wrongly.</h4><p>A simple formula often used to find the concentration of a solution is:</p><p>c = n / V (where c is the concentration, n is ‘number of moles’ (actually amount in mol) and V is the volume).</p><p>I’ve seen several variations of this in exams, e.g. c = V / n or n = c / V. The key to stating formulas correctly is to check the units. Concentration is normally expressed as mol dm<sup>−3</sup>. Once a student realises this the formula is redundant as mol dm<sup>−</sup><sup>3</sup> literally means the amount in mol divided by the volume in litres (dm<sup>3</sup>). Another example where the formula is often quoted wrongly is the relationship between the velocity of light (<em>c</em>), the frequency (ν) and the wavelength (λ).</p><p>Looking at the units it is obvious that velocity (m s<sup>−1</sup>) = wavelength (m) x frequency (s<sup>−1</sup>), i.e. <em>c</em> = <em>λν</em>.</p><hr class="hidden"><hr class="hidden"><h4>2. The formula is applied wrongly</h4><p>One of the most common examples of this is the formula M<sub>1</sub>V<sub>1</sub> = M<sub>2</sub>V<sub>2</sub> which students often use to solve titration problems. It does work in the simplest case when one mole of an acid is neutralised by one mole of a base,</p><p>e.g. HCl(aq) + NaOH(aq) → NaCl(aq) + H<sub>2</sub>O(l)</p><p>but certainly does not work when it comes to the neutralisation of diprotic acids,</p><p>e.g. H<sub>2</sub>SO<sub>4</sub>(aq) + 2NaOH(aq) → Na<sub>2</sub>SO<sub>4</sub>(aq) + 2H<sub>2</sub>O(l).</p><p>My advice is to never use it! Instead always work from first principles.</p><h4><span style="color:#FF0000;">Worked example:</span></h4><p>26.80 cm<sup>3</sup> of a solution of sulfuric acid was required to neutralise 25.00 cm<sup>3</sup> of 0.150 mol dm<sup>−3</sup> potassium hydroxide solution. Calculate the concentration of the sulfuric acid solution in mol dm<sup>-3</sup>.</p><p><strong>Step 1: </strong>Write the stoichiometric equation</p><p>H<sub>2</sub>SO<sub>4</sub>(aq) + 2KOH(aq) → K<sub>2</sub>SO<sub>4</sub>(aq) + 2H<sub>2</sub>O(l)</p><hr class="hidden"><p><strong>Step 2: </strong>Calculate the amount (in mol) of potassium hydroxide present.</p><p>1000 cm<sup>3</sup> of 0.150 mol dm<sup>−3</sup> KOH contains 0.150 mol</p><p>so 25.00 cm<sup>3</sup> contains (25.00/1000) x 0.150 = 3.75 x 10<sup>−3</sup> mol.</p><hr class="hidden"><p><strong>Step 3: </strong>Calculate the amount (in mol) of sulfuric acid required to neutralise the potassium hydroxide solution.</p><p>From the equation 1 mol of H<sub>2</sub>SO<sub>4</sub> neutralises 2 mol of KOH so amount of H<sub>2</sub>SO<sub>4</sub> required = ½ x 3.75 x 10<sup>−3</sup> = 1.875 x 10<sup>−3</sup> mol.</p><hr class="hidden"><p><strong>Step 4: </strong>Calculate the concentration of the sulfuric acid in mol dm<sup>−3</sup>.</p><p>26.80 cm<sup>3</sup> of H<sub>2</sub>SO<sub>4</sub> contains 1.875 x 10<sup>−3</sup> mol</p><p>1000 cm<sup>3</sup> of H<sub>2</sub>SO<sub>4</sub> contains (1000/26.80) x 1.875 x 10<sup>−3</sup> = 0.0700 mol</p><p>so the concentration of the sulfuric acid = 0.0700 mol dm<sup>−3</sup> (to 3 significant figures).</p><hr class="hidden"><hr class="hidden"><h4>3. A formula cannot be used at all.</h4><p>A back to basics stepwise approach is the only way to answer titration questions where a solid, rather than a solution, is being titrated as the formula M<sub>1</sub>V<sub>1</sub> = M<sub>2</sub>V<sub>2</sub> cannot be applied.</p><h4><span style="color:#FF0000;">Example:</span></h4><p>What mass of calcium carbonate will react exactly with 20.00 cm<sup>3</sup> of 0.200 mol dm<sup>−3</sup> hydrochloric acid?</p><p>Equation: 2HCl(aq) + CaCO<sub>3</sub>(s) → CaCl<sub>2</sub>(aq) + CO<sub>2</sub>(g) + H<sub>2</sub>O(l)</p><p>Amount of acid reacting = 20.00/1000 x 0.200 = 4.00 x 10<sup>−3</sup> mol</p><p>Since two mol of HCl react with one mol of CaCO<sub>3</sub></p><p>Amount of CaCO<sub>3</sub> that reacts = ½ x 4.00 x 10<sup>-3</sup> = 2.00 x 10<sup>−3</sup> mol</p><p><em>M</em>(CaCO<sub>3</sub>) = 40.08 + 12.01 + (3 x 16.00) = 100.09 g mol<sup>−1</sup></p><p>Mass of CaCO<sub>3</sub> that reacts with the acid = 100.09 x 2.00 x 10<sup>−3</sup> = 0.200 g ( to 3 significant figures).</p><hr class="hidden"><hr class="hidden"><h4>4.The wrong units are used.</h4><p class="MsoNormal">The classic example of where this often occurs is when students use the equation</p><p class="MsoNormal"><em>ΔG</em> = <em>ΔH </em>– <em>TΔS</em></p><p class="MsoNormal"><em>ΔG</em> and <em>ΔH</em> values are usually quoted in kJ mol<sup>−1</sup> but entropy values are normally quoted in J K<sup>−1</sup> mol<sup>−1.</sup> Students constantly need reminding that they must divide the entropy value by 1000 to convert it into kJ K<sup>−1</sup> mol<sup>−1</sup> when using it in the equation. Of course they also need to ensure the temperature is given in Kelvin not <sup>o</sup>C.</p><p class="MsoNormal">Other examples of formulas where units must be consistent are the gas equation <em>pV</em> = <em>nRT</em> and rate equations as the units of the rate constant depend upon the overall order of the reaction.</p><hr class="hidden"><hr class="hidden"><h4>5. Problems with the Henderson–Hasselbalch equation.</h4><p>This formula causes particular problems although strictly speaking calculations involving buffer solutions should only appear in Paper 3.</p><p>The theory of buffer solutions is covered at Higher Level in the AHL Topic 18 but buffer calculations only appear in two of the options in Paper 3. However even though buffers are not coved at Standard Level in the core, Option D (see <a href="../19184/ph-regulation-of-the-stomach-1.html" title="Options » Option D » pH regulation of the stomach">D.4 pH regulation of the stomach</a>) includes the application of the Henderson–Hasselbalch equation at both SL and HL whereas in option B (<a href="../19336/proteins-enzymes-ahl--1.html" title="Options » Option B » Proteins & enzymes (AHL) ">B.7 Proteins and enzymes</a>) it is only on the HL syllabus. The use of the Henderson–Hasselbalch equation in Option D can cause real problems for Standard Level students who have not covered either equilibrium calculations or the definitions of <em>K</em><sub>a</sub>, <em>K</em><sub>b</sub>, p<em>K</em><sub>a</sub> and p<em>K</em><sub>b</sub>.</p><p>The Henderson–Hasselbalch equation is given in Section 1 of the IB data booklet but it seems unwise for students to use it if they do not fully understand it. It is easy to use wrongly and and I have never taught it to my students as I prefer them to be able to work out all buffer calculations from first principles.</p><hr class="hidden"><h4><span style="color:#FF0000;">Example using first principles</span></h4><p>Calculate the pH of a buffer solution made by adding 20.0 cm<sup>3</sup> of 1.00 mol dm<sup>−3</sup> sodium hydroxide solution to 40.0 cm<sup>3</sup> of 1.00 mol dm<sup>-3</sup> ethanoic acid solution. Section 21 of the IB data booklet gives the p<em>K</em><sub>a</sub> of ethanoic acid = 4.76</p><p>(Standard level students need to understand that <em>K</em><sub>a</sub> is the equilibrium constant (acid dissociation constant) for a weak acid and that p<em>K</em><sub>a</sub> = − log<sub>10</sub><em>K</em><sub>a</sub> (this is rather similar to pH = − log<sub>10</sub>[H<sup>+</sup>(aq)]). The relationship <em>K</em><sub>a</sub> = 10<sup>−p<em>K</em>a</sup> is also helpful as the data booklet only lists p<em>K</em><sub>a</sub> values, not <em>K</em><sub>a</sub> values.)</p><hr class="hidden"><h4><span style="color:#FF0000;">Worked solution:</span></h4><p><strong>Step 1: </strong>Write the equation for the reaction.</p><p>CH<sub>3</sub>COOH(aq) + NaOH(aq) → CH<sub>3</sub>COONa(aq) + H<sub>2</sub>O(l)</p><p>After the reaction all the sodium hydroxide solution will have been neutralised to form sodium ethanoate and the excess ethanoic acid remains.</p><hr class="hidden"><p><strong>Step 2: </strong>Calculate the amounts of the sodium ethanoate and the excess ethanoic acid in the resulting solution.</p><p>Initial amount of NaOH = 20.0/1000 x 1.00 = 2.00 x 10<sup>−2</sup> mol</p><p>Initial amount of CH<sub>3</sub>COOH = 40.0/1000 x 1.00 = 4.00 x 10<sup>−2</sup> mol</p><p>Since all the NaOH reacts to form CH<sub>3</sub>COONa</p><p>Final amount of CH<sub>3</sub>COONa = 2.00 x 10<sup>−2</sup> mol</p><p>Final amount of CH<sub>3</sub>COOH = 4.00 x 10<sup>−2</sup> − 2.00 x 10<sup>−2</sup> = 2.00 x 10<sup>−2</sup> mol.</p><hr class="hidden"><p><strong>Step 3:</strong> Calculate the concentrations of the sodium ethanoate and the excess ethanoic acid in the resulting solution.</p><p>Final volume = 20.0 + 40.0 = 60.0 cm<sup>3 </sup> (assuming the volumes are exactly additive).</p><p>[CH<sub>3</sub>COONa(aq)] = 1000 / 60.0 x 2.00 x 10<sup>−2</sup> = 0.333 mol dm<sup>−3</sup></p><p>[CH<sub>3</sub>COOH(aq)] = 1000 / 60.0 x 2.00 x 10<sup>−2</sup> = 0.333 mol dm<sup>−3</sup></p><hr class="hidden"><p><strong>Step 4:</strong> Write the equilibrium expression for the dissociation of ethanoic acid.</p><p>CH<sub>3</sub>COOH(aq) ⇌ CH<sub>3</sub>COO<sup>−</sup>(aq) + H<sup>+</sup>(aq)</p><p><em>K</em><sub>a</sub> = [H<sup>+</sup>(aq)] x [CH<sub>3</sub>COO<sup>−</sup>(aq)] / [CH<sub>3</sub>COOH(aq)]</p><hr class="hidden"><p><strong>Step 5: </strong>Substitute the values for the concentration of the acid and the salt into the equilibrium expression to find [H<sup>+</sup>(aq)].</p><p><em>K</em><sub>a </sub>= [H<sup>+</sup>(aq)] x [CH<sub>3</sub>COO<sup>−</sup>(aq)] / [CH<sub>3</sub>COOH(aq)] = [H<sup>+</sup>(aq)] x 0.333 / 0.333 = [H<sup>+</sup>(aq)]</p><p><em>K</em><sub>a </sub>= 10<sup>−4.7</sup> so</p><p>[H<sup>+</sup>(aq)] = 10<sup>−4.76</sup> mol dm<sup>−3</sup></p><hr class="hidden"><p><strong>Step 6: </strong>Convert the hydrogen ion concentration into its pH value</p><p>pH = − log<sub>10</sub>[H<sup>+</sup>(aq)]</p><p>so pH = − log<sub>10</sub>10<sup>−4.76</sup> = 4.76</p><hr class="hidden"><p>Note that this example shows that at the half-equivalence point (i.e. when exactly half of the excess weak acid has been neutralised by the base, so that [acid] = [salt]) the pH = p<em>K</em><sub>a</sub>.</p><hr class="hidden"></div><hr class="hidden"><div class="pinkBg"><h1>Practice questions</h1><p class="MsoNormal"><span style="font-family:Arial">Answer the following questions from first principles (i.e. without using any mathematical formulas). The worked answers can be accessed by clicking on the ‘hidden’ symbol.</span></p><hr class="hidden"><p class="MsoNormal"><span style="font-family:Arial"></span></p><p class="MsoNormal"><strong>1.</strong><span style="font-family:Arial"> Calculate the concentration of an aqueous solution of sodium nitrate containing 1.70 g of sodium nitrate dissolved in 30.0 cm<sup>3</sup> of the solution. </span></p><section class="tib-hiddenbox"><p>M(NaNO<sub>3</sub>) = 22.99 + 14.01 + (3 x 16.00) = 85.00 g mol<sup>−1</sup></p><p>Amount of NaNO<sub>3</sub> in 30.00 cm<sup>3</sup> = 1.70 ÷ 85.00 = 0.0200 mol</p><p>Amount of NaNO<sub>3</sub> in 1000 cm<sup>3</sup> (1 dm<sup>3</sup>) = 1000 / 30.00 x 0.0200 = 0.667 mol</p><p>Concentration of NaNO<sub>3</sub>(aq) = 0.667 mol dm<sup>−3</sup>.</p></section><hr class="hidden"><hr class="hidden"><p><strong>2.</strong> Three separate solutions, 40.0 cm<sup>3</sup> of 2.00 mol dm<sup>−3</sup> HCl(aq), 50.0 cm<sup>3</sup> of 1.60 mol dm<sup>-3</sup> HCl(aq) and 30.0 cm<sup>3</sup> of 1.8 mol dm<sup>−3</sup> HCl(aq) are combined to make one solution. What is the concentration of this new solution?</p><section class="tib-hiddenbox"><p>Amount of HCl in 40.0 cm<sup>3</sup> of 2.00 mol dm<sup>−</sup><sup>3</sup> HCl(aq) = (40.0 / 1000) x 2.00 = 8.00 x 10<sup>−2 </sup>mol.</p><p>Amount of HCl in 50.0 cm<sup>3</sup> of 1.60 mol dm<sup>−</sup><sup>3</sup> HCl(aq) = (50.0 / 1000) x 1.60 = 8.00 x 10<sup>−2 </sup> mol.</p><p>Amount of HCl in 30.0 cm<sup>3</sup> of 1.8 mol dm<sup>−</sup><sup>3</sup> HCl(aq) = (30.0 / 1000) x 1.80 = 5.40 x 10<sup>−2 </sup> mol.</p><p>Total amount of HCl present = (8.00 + 8.00 + 5.40) x 10<sup>−2</sup> = 0.214 mol</p><p>Total volume = 40.0 + 50.0 + 30.0 = 120 cm<sup>3</sup></p><p>Concentration = 0.214 x 1000/120 = 1.78 mol dm<sup>−</sup><sup>3</sup>.</p></section><hr class="hidden"><hr class="hidden"><p><strong>3. </strong>What volume of 0.250 mol dm<sup>−3</sup> sulfuric acid is required to neutralise exactly 15.0 cm<sup>3</sup> of 0.150 mol dm<sup>−3</sup> barium hydroxide solution?</p><section class="tib-hiddenbox"><p>H<sub>2</sub>SO<sub>4</sub>(aq) + Ba(OH)<sub>2</sub> → BaSO4(aq) + 2H<sub>2</sub>O(l)</p><p>Amount of Ba(OH)<sub>2</sub> in 15.0 cm<sup>3</sup> = (15.0 / 1000) x 0.150 = 2.25 x 10<sup>−3</sup> mol</p><p>1 mol of H<sub>2</sub>SO<sub>4</sub> reacts with 1 mol of Ba(OH)<sub>2</sub></p><p>Amount of H<sub>2</sub>SO<sub>4</sub> required = 2.25 x 10<sup>−3</sup> mol</p><p>Volume of 0.250 mol dm<sup>−3</sup> H<sub>2</sub>SO<sub>4</sub> required = (1000 / 0.250) x 2.25 x 10<sup>−3</sup> = 9.00 cm<sup>3</sup>.</p></section><hr class="hidden"><hr class="hidden"><p><strong>4. </strong>What volume of carbon dioxide measured at STP will be evolved when 2.10 g of sodium hydrogen carbonate, NaHCO<sub>3</sub> is reacted with excess hydrochloric acid?</p><section class="tib-hiddenbox"><p>NaHCO<sub>3</sub>(s) + HCl(aq) → NaCl(aq) + CO<sub>2</sub>(g) + H<sub>2</sub>O(l)</p><p>M(NaHCO<sub>3</sub>) = 22.99 + 1.01 + 12.01 + (3 x 16.00) = 84.01 g mol<sup>−1</sup></p><p>Amount of NaHCO<sub>3</sub> = 2.10 ÷ 84.01 = 0.0250 mol</p><p>1 mol of NaHCO<sub>3</sub> reacts to produce 1 mol of CO<sub>2</sub></p><p>Amount of CO<sub>2</sub> evolved = 0.0250 mol</p><p>1 mol of any gas occupies 22.7 dm<sup>3</sup> at STP (from Section 2 of the IB data booklet)</p><p>Volume of CO<sub>2</sub> evolved = 0.568 dm<sup>3</sup> = 568 cm<sup>3</sup></p></section><hr class="hidden"><hr class="hidden"><p><strong>5. (a) </strong>What will be the pH of the buffer solution prepared by adding 25.00 cm<sup>3</sup> of 1.25 mol dm<sup>−3</sup> NaOH(aq) to 60.00 cm<sup>3</sup> of 1.20 mol dm<sup>−3</sup> CH<sub>3</sub>COOH(aq). (<em>K</em><sub>a</sub> of CH<sub>3</sub>COOH = 1.74 x 10<sup>−5 </sup>at 298 K)</p><section class="tib-hiddenbox"><p>CH<sub>3</sub>COOH(aq) + NaOH(aq) → CH<sub>3</sub>COONa(aq) + H<sub>2</sub>O(l)</p><p>Initial amount of NaOH = 25.0/1000 x 1.25 = 3.125 x 10<sup>−2</sup> mol</p><p>Initial amount of CH<sub>3</sub>COOH = 60.0/1000 x 1.20 = 7.200 x 10<sup>−2</sup> mol</p><p>Since all the NaOH reacts to form CH<sub>3</sub>COONa</p><p>Final amount of CH<sub>3</sub>COONa = 3.125 x 10<sup>−2</sup> mol</p><p>Final amount of CH<sub>3</sub>COOH = 7.200 x 10<sup>−2</sup> − 3.125 x 10<sup>−2</sup> = 4.075 x 10<sup>−2</sup> mol</p><p>Final volume = 25.0 + 60.0 = 85.0 cm<sup>3 </sup> (assuming the volumes are exactly additive).</p><p>[CH<sub>3</sub>COONa(aq)] = 1000 / 85.0 x 3.125 x 10<sup>−2</sup> = 0.3676 mol dm<sup>−3</sup></p><p>[CH<sub>3</sub>COOH(aq)] = 1000 / 85.0 x 4.075 x 10<sup>−2</sup> = 0.4794 mol dm<sup>−3</sup></p><p><em>K</em><sub>a </sub>= [H<sup>+</sup>(aq)] x [CH<sub>3</sub>COO<sup>−</sup>(aq)] / [CH<sub>3</sub>COOH(aq)] = [H<sup>+</sup>(aq)] x 0.3676 / 0.4794 = 0.767 x [H<sup>+</sup>(aq)]</p><p><em>K</em><sub>a</sub> of CH<sub>3</sub>COOH = 1.74 x 10<sup>−5</sup></p><p>[H<sup>+</sup>(aq)] = 1.74 x 10<sup>−5</sup> / 0.767 = 2.27 x 10<sup>−5</sup></p><p>pH = − log<sub>10</sub>[H<sup>+</sup>(aq)] = 4.64</p></section><p><strong>5.(b) </strong>The same buffer solution can be prepared by dissolving solid sodium ethanoate in a solution of ethanoic acid. What mass of sodium ethanoate would need to be dissolved in 50.0 cm<sup>3</sup> of 1.20 mol dm<sup>−3</sup> CH<sub>3</sub>COOH(aq) to give a buffer solution with a pH of 4.64? Assume that when the salt is dissolved it does not affect the volume of the solution.</p><section class="tib-hiddenbox"><p>CH<sub>3</sub>COOH(aq) ⇌ CH<sub>3</sub>COO<sup>−</sup>(aq) + H<sup>+</sup>(aq)</p><p><em>K</em><sub>a</sub> = [H<sup>+</sup>(aq)] x [CH<sub>3</sub>COO<sup>−</sup>(aq)] / [CH<sub>3</sub>COOH(aq)]</p><p>CH<sub>3</sub>COOH(aq) = 1.20 mol dm<sup>−3</sup> and since the pH must be 4.64, [H<sup>+</sup>(aq)] = 10<sup>−4.64</sup> and the value of <em>K</em><sub>a</sub> is given in <strong>5.(a)</strong>.</p><p><em>K</em><sub>a</sub> = 1.74 x 10<sup>−5</sup> = 10<sup>−4.64</sup> x [CH<sub>3</sub>COO<sup>−</sup>(aq)] / 1.20</p><p>[CH<sub>3</sub>COO<sup>−</sup>(aq)] = 1.74 x 10<sup>−5</sup> x 1.20 / 10<sup>−4.64</sup> = 0.911 mol dm<sup>−3</sup></p><p><em>M</em>(CH<sub>3</sub>COONa) = (2 x 12.01) + (3 x 1.01) + (2 x 16.00) + 22,99 = 82.04 g mol<sup>∼1</sup></p><p>Mass of CH<sub>3</sub>COONa required in 50.0 cm<sup>3</sup> = 0.911 x 82.04 x 50.0 / 1000 = 3.74 g</p></section><hr class="hidden"></div></section></article><section id="media-extras"><div class="page-actions no-print navbar inline hidden-desktop"><div class="navbar-inner"><ul class="nav"><li><a class="presentation" href="#" onclick="return false;"><i class="fa fa-desktop"></i></a></li><li><a class="print-section-blog" href="#" onclick="return false;"><i class="fa fa-print"></i></a></li><li><a class="page-bookmarker" data-ticket="IB Docs (2) Team" data-pid="32586" href="#" onclick="return false;"><i class="fa fa-star"></i></a></li><li><a class="personal-notes" href="#" onclick="return false;"><i class="fa fa-file-text"></i></a></li><li><a class="" data-toggle="modal" href="#modal-feedback" onclick="return false;"><i class="fa fa-envelope-o"></i></a></li><li class="dropdown"><a class="dropdown-toggle" data-toggle="dropdown" data-target="#" href="#"><i class="fa fa-share-alt"></i></a><ul class="dropdown-menu" role="menu"><li><a class="" target="_blank" title="Share on Twitter" href="https://twitter.com/share?text=%22Misuse+of+formulas%22+-+via+%40InThinker+%23chemistry%0A&url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas"><i class="fa fa-twitter-square"></i><span>Twitter</span></a></li><li><a class="" target="_blank" title="Share on Facebook" href="https://www.facebook.com/sharer.php?u=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas&t=Misuse+of+formulas"><i class="fa fa-facebook-square"></i><span>Facebook</span></a></li><li><a class="" href="http://www.linkedin.com/shareArticle?mini=true&url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas"><i class="fa fa-linkedin-square"></i><span>LinkedIn</span></a></li><li><a class="" href="https://plus.google.com/share?url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas"><i class="fa fa-google-plus-square"></i><span>Google +</span></a></li><li><a class="" href="mailto:?subject=Misuse of formulas&body=Students often use mathematical formulas to solve chemical problems in exams and sometimes arrive at the wrong answer. This page looks at why this is so and encourages students to work always from first principles rather...%0Ahttps%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F32586%2Fmisuse-of-formulas"><i class="fa fa-envelope"></i><span>Email</span></a></li></ul></li><li><a class="" href="chemistry/teaching-materials"><i class="fa fa-puzzle-piece colored"></i></a></li></ul></div></div><div style="border-top: solid 1px #eee;border-bottom: solid 1px #eee;padding: 4px 0 4px 0;line-height: 1em;color: #666;font-size: .8em"><small><em>All materials on this website are for the exclusive use of teachers and students at subscribing schools for the period of their subscription. Any unauthorised copying or posting of materials on other websites is an infringement of our copyright and could result in your account being blocked and legal action being taken against you.</em></small></div></section><section id="comments"></section></div><!-- /#main-column -->
</div>
</div><!-- /#content -->
</div>
</div>
<div id="footer">
<div class="wmap">
<div class="layout-wrapper">
<p>
© <script>document.write(new Date().getFullYear())</script> <em>InThinking / IB Documents (2) Team | Version: 31.01.2023</em>
|
<a target="_self" href="/subscribe/about-us">
About us
</a>
|
<a target="_self" href="/subscribe/legal">
Legal
</a>
|
<a target="_self" href="/subscribe/contact">
Contact
</a>
</p>
<p>
<a class="social" target="_blank" href="https://twitter.com/inthinker">
<img src="../../../social/twitter-square-1.svg"> Twitter
</a>
<a class="social" target="_blank" href="https://www.facebook.com/inthinking.net">
<img src="../../../social/facebook-square-1.svg"> Facebook
</a>
<a class="social" target="_blank" href="https://www.linkedin.com/company/9s4we1">
<img src="../../../social/linkedin-square-1.svg"> LinkedIn
</a>
</p>
</div>
</div>
</div>
<input id="tzoffset" type="hidden" value="-36000"><div id="modal-session-expired" class="modal fade" tabindex="-1" role="dialog" data-backdrop="static" data-keyboard="false">
<div class="modal-dialog" role="document">
<div class="modal-content">
<div class="modal-header">
<h3 style="margin-top: 0">Your session has expired</h3>
</div>
<div class="modal-body" style="padding: 10px;">
<p>You will have to reload and log in again.</p>
</div>
<div class="modal-footer">
<a id="session-expired" class="btn btn-danger pull-right" href="#">
<i class="fa fa-refresh"></i> Reload
</a>
</div>
</div>
</div>
</div>
<!-- Loading scripts at the end of the body means faster page loading -->
<script src="../../../js/jquery-1.10.2.min-1.js"></script>
<script src="../../../js/bootstrap.min-1.js"></script>
<script type="text/javascript" src="../../../js/jq-fancybox/jquery.fancybox.pack-1.js"></script>
<script>var pageId = 32586;</script><script src="../../../js/autosize.min-1.js" media="screen"></script><script src="../../../js/user/section-faves.min-1.js?v=202110111730"></script><script src="../../../js/edit/table-of-contents.min-1.js"></script><script type="text/javascript" src="../../../assets/build/app-1.js?v=202204141130"></script><script type="text/javascript" src="../../../assets/js/ckeditor5-utils.min-1.js?v=20211202"></script><script type="text/javascript" src="../../../js/tib-fullscreen/tib-fullscreen.min-1.js?v=202109221648"></script><script src="../../../js/sidemenu/sidemenu.min-1.js?v=202011301145"></script><script src="../../../js/header-circle.min-1.js?v=20220113"></script><script src="../../../js/password-toggler.min-1.js?v=20220929"></script><script type="text/javascript" src="../../../js/cookies.min-1.js"></script>
<script type="text/javascript">
// The cookies alert
if (! readCookie("displayCookieConsent") && ! readCookie("y") ) {
var cookieMSG = "We use cookies. By continuing to use this website you are giving consent to cookies being used.";
setTimeout(function() {
$.ajax({
cache: true,
url: "js/cookiechoices.js",
dataType: "script",
success: function () {
cookieChoices.showCookieConsentBar(cookieMSG, 'close', 'Read more', "chemistry/legal#cookies");
}
});
}, 2000);
}
</script><script>var sAJAX='/pages/activity/user-stats-page.php?t=IB Docs (2) Team&x=3340';var sData='0ebg+I>F/4F[IxZ4hvT)hIn82Oc2UjpCqiT2UM]en-liIxZ)hInQ2ir)oi+)q|ZeoIT6+I][UxbMLNbYoiQChNf[5[/[UxbOqNuc2|w6IicY/4FMUxbeqIn9LIb4qTZ80Ipc/4F[2vwOqt/6/Obc2iZQ2|ncIicY/4F[]M/Q5V+[ak==';var loopSecs = 30;var lsKey = '951fd9f6507d9576e409ac025ce98306';</script><script src="../../../js/user/user-stats-page.min-1.js?v=202102101800"></script><script>var sessionUpdateSecs = 600;</script><script type="text/javascript" src="../../../js/session-updater-1.js?v=20200831"></script>
<script type="text/javascript">
$(document).ready(function(){
function padLeft(str,max){return str.length<max?padLeft("0"+str,max):str}function padRight(str,max){return str.length<max?padRight(str+"0",max):str}$("body").on("click",'a[href="#"], a.fancybox-nav, a[data-toggle="tab"], a[data-toggle="dropdown"], a[data-toggle="collapse"], a[data-toggle="modal"]',(function(e){e.preventDefault()}));var topmenuOffset=0,topmenuHeight=0;function fixDiv(t,h){$(window).scrollTop()<topmenuOffset||$("#topmenu ul.level-1").is(":visible")?($("#topmenu").css({position:"",width:""}),$("#topmenu").removeClass("fixed-top"),$("body").css({"padding-top":"0"})):($("#topmenu").css({position:"fixed",top:"0",width:$("#topmenu").width()+"px"}),$("#topmenu").addClass("fixed-top"),$("body").css({"padding-top":topmenuHeight+"px"}))}function fixSearchNav(){var searchMenuTop=topmenuOffset+topmenuHeight,searchMenuH=$("#nav-menu-search").is(":visible")?$("#nav-menu-search").outerHeight():0;$(window).scrollTop()>searchMenuTop-topmenuHeight?($("#nav-menu-search").css({position:"fixed",top:topmenuHeight+"px",left:"0",right:"0"}),$("#nav-menu-search").addClass("fixed-top"),$("body").css("padding-top",topmenuHeight+searchMenuH+"px")):($("#nav-menu-search").css({position:""}),$("#nav-menu-search").removeClass("fixed-top"),$("body").css("padding-top","0"))}$("#topmenu").length&&(topmenuOffset=$("#topmenu").offset().top,topmenuHeight=$("#topmenu").outerHeight(),fixDiv(),$(window).scroll((function(){fixDiv(),fixSearchNav()}))),$("a.toggle-menu-search").on("click",(function(e){e.preventDefault(),$("#nav-menu-search").slideToggle("fast",(function(){$(this).find('input[name="s"]').focus()}))}));var menuH=$("#topmenu").height(),itemH=$("#topmenu > nav > ul > li").height();function fancyScrollTo(id){$("html, body").animate({scrollTop:$("#"+id).offset().top-300},300)}function printSectionBlog(){var w=$(window).width()/2,h,windowSettings="height="+($(window).height()-100)+", width="+w+", left=0, top=0, resizable=no, ";windowSettings+="scrollbars=yes, toolbar=no, menubar=no, location=no, ",windowSettings+="directories=no, status=yes";var myWindow=window.open("","Page printer",windowSettings),containerHtml=["<html>","<head>","<title>Page printer</title>",'<link rel="stylesheet" type="text/css" href="'+window.location.origin+'/css/style.min.css?v=202211152130">','<link rel="stylesheet" type="text/css" href="'+window.location.origin+"/css/style"+SITE_TAG+'.min.css?v=202104061357">','<link rel="stylesheet" type="text/css" href="'+window.location.origin+'/css/snippets.min.css?v=202210181500">','<link rel="stylesheet" type="text/css" href="'+window.location.origin+'/css/article.min.css?v=202210181500">',"</head>","<body>",$("section#main-content").html().replace(/<span\sclass="MJX_Assistive_MathML".*?<\/span>/g,""),"</body>","</html>"].join("");containerHtml=containerHtml.replace(/src="files\//gi,'src="'+window.location.origin+"/files/"),myWindow.document.write(containerHtml),myWindow.document.close(),myWindow.focus(),setTimeout((function(){$.when(myWindow.print()).then(myWindow.close())}),1e3)}function PopupPrint(target){window.print()}$("#topmenu > nav > ul > li").each((function(){if(menuH>itemH&&$(this).position().top<1){var i=itemH+1;$(this).find("ul:first").css("margin-top","-"+i+"px")}})),$("#topmenu > nav > ul > li").on("mouseenter mouseleave",(function(e){var submenu=$("ul:first",this),submenuW=submenu.width();$(this).offset().left+submenuW>$(window).width()&&(submenu.css("right","0"),submenu.find("ul").each((function(){if(!$(this).hasClass("fixed")){var l=$(this).width()+submenuW;$(this).css("margin-left","-"+l+"px"),$(this).addClass("fixed")}})))})),$("a.showhider").click((function(e){e.preventDefault();var box="#"+$(this).attr("rel"),show='<i class="fa fa-eye"></i>',hide='<i class="fa fa-eye-slash"></i>';$(box).slideToggle("fast"),$(this).html($(this).html()==show?hide:show),$(this).attr("title","Show"==$(this).attr("title")?"Hide":"Show")})),$("a.scroll-to").click((function(e){e.preventDefault();var n=$("#"+$(this).data("target")).offset().top-70;$("html, body").animate({scrollTop:n},300)})),$("a.print-section-blog").click((function(e){e.preventDefault(),printSectionBlog()})),$(".print-button").click((function(e){var target;e.preventDefault(),PopupPrint("#"+$(this).data("target-id"))})),$(".alert.alert-success").delay(6e3).hide("fast",fixDiv());var fancyParent=1==$("body").find($("#main-article")).length?"#main-article":"body",fancyOptions={loop:!1,openEffect:"elastic",closeEffect:"elastic",nextEffect:"fade",prevEffect:"fade",parent:fancyParent,helpers:{title:{type:"inside"}}};if($("ul.gallery").each((function(){var rel=$(this).find("li:first-child > a:first-child").attr("rel");$('ul.gallery a.fancy[rel="'+rel+'"]').fancybox(fancyOptions)})),$(".carousel.slide").each((function(){var rel="gallery-"+$(this).data("id");$('.carousel.slide a.fancy[rel="'+rel+'"]').fancybox(fancyOptions)})),$("img.pop").parent("a").each((function(){$(this).attr("title",$(this).children("img").attr("alt"))})),$("img.pop").parent("a").fancybox({loop:!1,helpers:{title:{type:"inside"}}}),!are_cookies_enabled()){var msg='<div class="alert alert-error"><i class="fa fa-warning"></i> Your browser does not accept cookies from this site. Please enable cookies to log in.</div><div class="alert alert-info"><i class="fa fa-question-circle"></i> Enabling cookies in <a target="_blank" style="margin: 0; padding: 0;" href="https://support.mozilla.org/en-US/kb/enable-and-disable-cookies-website-preferences">Firefox</a>, <a target="_blank" style="margin: 0; padding: 0;" href="https://support.google.com/accounts/answer/61416?hl=en">Chrome</a>, <a target="_blank" style="margin: 0; padding: 0;" href="http://windows.microsoft.com/en-us/windows-vista/block-or-allow-cookies">Explorer</a></div>';$("#modal-login .modal-header").append(msg)}if($(".panel-expandable > .panel-heading").click((function(e){e.preventDefault();var panel=$(this).closest(".panel-expandable"),expandables=panel.hasClass("panel-has-footer")?".panel-body, .panel-footer":".panel-body";panel.find(".panel-body").is(":visible")?(panel.find(expandables).slideUp("fast"),panel.find(".expander > .fa-minus").removeClass("fa-minus").addClass("fa-plus")):(panel.find(expandables).slideDown("fast"),panel.find(".expander > .fa-plus").removeClass("fa-plus").addClass("fa-minus"))})),$("#modal-find-out-more").css({width:.8*$("#container").width()+"px","margin-left":-.4*$("#container").width()+"px"}),$(".modal-xxl").length){var modalTopPos=Math.round(.07*$(window).height());$(window).width()>1200&&$(".modal-xxl").css({"max-width":$(window).width()>960?"960px":$(window).width()+"px",width:$(window).width()>960?"960px":$(window).width()+"px","margin-left":$(window).width()>960?"-480px":Math.round($(window).width()/2)}),$(".modal-xxl").css("top",modalTopPos+"px"),$(".modal-xxl").on("shown",(function(){var mHeaderH=$(this).find(".modal-header").outerHeight(),mBody=$(this).find(".modal-body"),mBodyH=mBody.outerHeight(),mFooterH=$(this).find(".modal-footer").outerHeight(),bottomOfTheModal=modalTopPos+mHeaderH+mBodyH+mFooterH;if(bottomOfTheModal<$(window).height())mBodyH+=$(window).height()-bottomOfTheModal-60,mBody.css("max-height",mBodyH+"px");else{$(window).scrollTop(0),modalTopPos=10,$(".modal-xxl").css("top",modalTopPos+"px"),bottomOfTheModal=modalTopPos+mHeaderH+mBodyH+mFooterH,availableScroll=bottomOfTheModal-$(window).height()+modalTopPos;var lastPos=-1;$(window).on("scroll",(function(){var s=$(window).scrollTop()>availableScroll?availableScroll:$(window).scrollTop();newPos=modalTopPos-s,newPos!=lastPos&&($(".modal-xxl").css("top",newPos+"px"),lastPos=newPos)}))}}))}function popupHelp(url,title,w,h){var dualScreenLeft=void 0!==window.screenLeft?window.screenLeft:screen.left,dualScreenTop=void 0!==window.screenTop?window.screenTop:screen.top,width,height,left=(window.innerWidth?window.innerWidth:document.documentElement.clientWidth?document.documentElement.clientWidth:screen.width)/2-w/2+dualScreenLeft,top=(window.innerHeight?window.innerHeight:document.documentElement.clientHeight?document.documentElement.clientHeight:screen.height)/2-h/2+dualScreenTop,newWindow=window.open(url,title,"menubar=no,location=no,resizable=0, width="+w+", height="+h+", top="+top+", left="+left);return window.focus&&(newWindow?newWindow.focus():$('<div class="alert alert-warning" style="margin-bottom: 0px;"><p class="help-block">Pop Up blocked. Please allow Pop Ups in your browser settings.</p></div>').insertBefore("body")),newWindow}if($(".open-student-access-help").click((function(e){e.preventDefault();var h=$(window).height()-20,w=$(window).width()<1280?$(window).width():1280;popupHelp(helpURL,"Student Access Help",w,h)})),$(".pop-up-help").click((function(e){e.preventDefault();var url=$(this).attr("href"),title=$(this).data("title"),h=$(window).height()-20,w;popupHelp(url,title,$(window).width()<1280?$(window).width():1280,h)})),$("section.tib-hiddenbox").length){var count=0;$($("section.tib-hiddenbox").get().reverse()).each((function(){var box=$(this),revealButton;$("<a />").attr("class","btn showhider").attr("rel","hiddenBoxContent"+count).attr("style","margin-bottom: 0;").html('<i class="fa fa-eye"></i>').insertBefore(box);var newContainer=$("<div />").attr("class","hidden-content").attr("id","hiddenBoxContent"+count).html(box.html());newContainer.hide(),newContainer.insertBefore(box),box.remove(),count++})),$("a.showhider").on("click",(function(e){var container=$("#"+$(this).attr("rel"));container.is(":hidden")?(container.fadeIn("fast"),$(this).html('<i class="fa fa-eye-slash"></i>')):(container.fadeOut("fast"),$(this).html('<i class="fa fa-eye"></i>'))}))}
$('.toc-switcher').click(function(e){
e.preventDefault();
$('.toc > ol').slideToggle('fast');
$(this).find('i:last-child').toggleClass('fa fa-chevron-circle-up').toggleClass('fa fa-chevron-down');
$(this).attr('title', $(this).attr('title') == 'Show table of contents' ? 'Hide table of contents' : 'Show table of contents');
});function loadComments(){$.get("pages/comment.php",{action:"get-list",ticket:"IB Docs (2) Team",site_with_comments:"1",general_id:"3",sitename:"chemistry",section_id:"32586"},(function(t){"1"==t.success?($("#comments").html(t.html),"undefined"!=typeof CKEDITOR&&initCommentsEditor()):alert("Error (lc1): please contact support")}),"json")}$(document).ready((function(){loadComments()}));let commentEditor={};function initCommentsEditor(){const t=document.querySelector("#comment-content");t&&CKEDITOR.BasicEditor.create(t,{toolbar:{viewportTopOffset:50,items:["bold","italic","link","subscript","superscript"]},link:{decorators:{addLinkNoFollow:{mode:"automatic",callback:function(t){if(null!=t)return["http://","http://www","https://","https://www","ftp:"].some((o=>t.startsWith(o)))},attributes:{target:"_blank",class:"ck-link",rel:"nofollow"}}}}}).then((function(t){commentEditor=t,commentEditor.execute("heading",{value:"paragraph"})})).catch((function(t){console.error(t)}))}function replaceComment(content,commentId){$("#cancel-comment-post").trigger("click"),$("#comm-"+commentId+" > .comment-content div.comment-text").html(content)}function placeComment(html,fatherId){$("#comment-form").hide(),$("#comment-form textarea").val(""),fatherId>0?($("#comments #comm-"+fatherId).append(html),$("#comments").append($("#comment-form"))):$("#comments").append(html).append($("#comment-form")),$(".comment .fa-arrow-down").removeClass("fa-arrow-down").addClass("fa-reply"),$(".comment-content").removeClass("marked"),$("#comment-form").show("fast")}function update_sticky_comments(arrIds,mode){$.post("pages/edit/update-sticky-comments.php?mode="+mode,{ids:arrIds,ticket:$("#comment-ticket").val()},(function(data){1==data.success?("set"==data.mode&&$("#sticky-"+data.id).parents("div.comment").each((function(e){$(this).find("a.pull-right").first().addClass("sticky"),$(this).find("a.pull-right").first().attr("title","Unmark as important")})),"unset"==data.mode&&($("#sticky-"+data.id).removeClass("sticky"),$("#sticky-"+data.id).attr("title","Mark as important"),$("#sticky-"+data.id).closest("div.comment").find("div.comment").each((function(e){$(this).find("a.pull-right").first().removeClass("sticky"),$(this).find("a.pull-right").first().attr("title","Mark as important")})))):alert(data.error)}),"json")}"undefined"!=typeof CKEDITOR&&initCommentsEditor(),$("section#comments").on("click","#edit-comment",(function(e){e.preventDefault();var commentId=$("form#comment-form #comment-mode").val(),commentContent=commentEditor.getData(),ticket=$("#comment-ticket").val(),sectionId=$("#section-id").val();$.post("pages/comment.php",{action:"edit",comment_id:commentId,content:commentContent,ticket:ticket},(function(data){"0"==data.success?alert(data.error):replaceComment(data.text,commentId)}),"json")})),$("section#comments").on("click","a.edit-comment",(function(e){e.preventDefault(),$(".comment .hidden").removeClass("hidden");var commentId=$(this).data("comment-id"),form=$("form#comment-form"),text=$("#comm-"+commentId+" > .comment-content div.comment-text").html();commentEditor.setData(text),$("form#comment-form textarea").val(""),$("form#comment-form textarea").val(text),$("#comm-"+commentId+" > .comment-content > img").addClass("hidden"),$("#comm-"+commentId+" > .comment-content > div.comment-text").addClass("hidden"),$("#comm-"+commentId+" > .comment-footer").addClass("hidden"),$("#comm-"+commentId+" > .comment-content").append(form),$("form#comment-form #submit-comment").hide(),$("form#comment-form #edit-comment").show(),$("form#comment-form #cancel-comment-post").show(),$("form#comment-form #comment-mode").val(commentId),fancyScrollTo("comment-form"),$("form#comment-form textarea").focus()})),$("section#comments").on("click","#submit-comment",(function(e){e.preventDefault();var commentContent=commentEditor.getData(),fatherId=$("#father-comment").val(),ticket=$("#comment-ticket").val(),sectionId=$("#section-id").val();$.post("pages/comment.php",{action:"post",section_id:sectionId,father_id:fatherId,content:commentContent,ticket:ticket},(function(data){if("0"==data.success)alert(data.error);else{commentEditor.setData(""),placeComment(data.html,fatherId),$("form#comment-form #cancel-comment-post").hide();var n=0;$("#n-comments").text().length>0&&(n=parseInt($("#n-comments").text())),$("#n-comments").text(n+1)}}),"json")})),$("section#comments").on("click","a.reply-comment",(function(e){e.preventDefault(),$(".comment .fa-arrow-down").removeClass("fa-arrow-down").addClass("fa-reply"),$(".comment-content").removeClass("marked");var form=$("form#comment-form"),fatherId=$(this).parent().parent(".comment").attr("rel");form.find("#father-comment").val(fatherId),$(this).parent().parent(".comment").find("> .reply-area").append(form),$(this).find(".fa-reply").removeClass("fa-reply").addClass("fa-arrow-down"),$(this).parent().prev(".comment-content").addClass("marked"),$("form#comment-form #cancel-comment-post").show(),fancyScrollTo("comment-form"),$("form#comment-form textarea").focus()})),$("section#comments").on("click","#cancel-comment-post",(function(e){e.preventDefault(),$(".comment .hidden").removeClass("hidden"),$(".comment .fa-arrow-down").removeClass("fa-arrow-down").addClass("fa-reply"),$(".comment-content.marked").removeClass("marked"),commentEditor.setData("");var form=$("form#comment-form");$("section#comments").append(form),$("form#comment-form #father-comment").val("0"),$("form#comment-form textarea").val(""),$("form#comment-form #comment-mode").val("new"),$("#edit-comment").hide(),$(this).hide(),$("#submit-comment").show()})),$("section#comments").on("click","a.delete-comment",(function(e){var commentId=$(this).data("comment-id"),isFather=$("#comm-"+commentId).children(".comment").length>0,ticket=$("#comment-ticket").val(),msg="You are going to delete a comment.\n\nThis action cannot be undone.\n\nAre you sure?";isFather&&(msg="You are going to delete a comment and all its replies.\n\nThis action cannot be undone.\n\nAre you sure?"),confirm(msg)&&$.post("pages/comment.php",{action:"delete",comment_id:commentId,is_father:isFather,ticket:ticket},(function(data){if("0"==data.success)alert(data.error);else{$("#comm-"+commentId+".comment").replaceWith(data.text);var n=0;$("#n-comments").text().length&&(n=parseInt($("#n-comments").text())),$("#n-comments").text(n-parseInt(data.deleted))}}),"json"),e.preventDefault(),e.stopPropagation()})),$("section#comments").on("click","a.pull-right",(function(e){e.preventDefault();var arrayIds=[];$(this).hasClass("sticky")?(arrayIds.push($(this).closest("div.comment").attr("rel")),$(this).closest("div.comment").find("div.comment").each((function(e){arrayIds.push($(this).attr("rel"))})),update_sticky_comments(arrayIds,"unset")):($(this).parents("div.comment").each((function(e){arrayIds.push($(this).attr("rel"))})),update_sticky_comments(arrayIds,"set"))}));$('#tl-tabs a').click(function (e) {e.preventDefault();$(this).tab('show');});$('img.ico[src="/img/icons/comments.png"]').each((function(){var comment=$(this).attr("title");$(this).removeAttr("title"),$(this).wrap('<a class="tib-popover" href="#" data-content="'+comment+'" data-togle="popover" data-placement="top" />')})),$('img.ico[src="img/icons/comments.png"]').each((function(){var comment=$(this).attr("title");$(this).removeAttr("title"),$(this).wrap('<a class="tib-popover" href="#" data-content="'+comment+'" data-togle="popover" data-placement="top" />')})),$(".tib-popover").popover({html:!0,trigger:"hover",delay:{show:300,hide:300},placement:function(context,source){var position=$(source).position();return position.top>200?"top":position.left<515?"right":position.top<200?"bottom":position.left>515?"left":"top"}}).click((function(e){e.preventDefault()}));var carouselTime=6500;$("div.carousel.slide").carousel({interval:carouselTime}),$(".tib-indicators > img").click((function(){var index=$(this).index(),container;$(this).closest(".carousel.slide").carousel(index)}));
$('a.btn.showhider').click(function(e) {
var showHiderId = $( this ).attr('rel');
if ( $('#'+showHiderId).find('iframe').length > 0 ) {
$('#'+showHiderId+' iframe').each(function() {
if ( $(this).attr('src').indexOf('.pdf') > 0 ) {
this.contentWindow.location.reload(true);
}
});
}
});
var hTopmenu = $('#topmenu').height();
var n = 0;
$('nav.top-nav > ul > li').each(function(k, e) {
if (n > 1) {
var diff = hTopmenu-(e.offsetTop+e.offsetHeight);
$(e).find(' > ul ').css('margin-top', '-'+diff+'px');
}
n++;
});
});
</script>
</body>
</html>