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</div><h2>HL Paper 2</h2><div class="specification">
<p class="p1">Chloroethene, C<sub><span class="s1">2</span></sub>H<sub><span class="s1">3</span></sub>Cl, is an important organic compound used to manufacture the polymer poly(chloroethene).</p>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">State an equation for the reaction of ethanoic acid with water.</p>
<div class="marks">[1]</div>
<div class="question_part_label">d.i.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Calculate the pH of \({\text{0.200 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) ethanoic acid \(({\text{p}}{K_{\text{a}}} = 4.76)\).</p>
<div class="marks">[3]</div>
<div class="question_part_label">d.ii.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Determine the pH of a solution formed from adding \({\text{50.0 c}}{{\text{m}}^{\text{3}}}\) of \({\text{1.00 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) ethanoic acid, \({\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH(aq)}}\), to \({\text{50.0 c}}{{\text{m}}^{\text{3}}}\) of \({\text{0.600 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) sodium hydroxide, NaOH(aq).</p>
<div class="marks">[4]</div>
<div class="question_part_label">e.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">(if acid added) \({\text{C}}{{\text{H}}_3}{\text{CO}}{{\text{O}}^ - } + {{\text{H}}^ + } \to {\text{C}}{{\text{H}}_3}{\text{COOH}}\);</p>
<p class="p1">(if alkali added) \({\text{C}}{{\text{H}}_3}{\text{COOH}} + {\text{O}}{{\text{H}}^ - } \to {\text{C}}{{\text{H}}_3}{\text{CO}}{{\text{O}}^ - } + {{\text{H}}_2}{\text{O}}\);</p>
<p class="p1"><em>Explanation marks cannot be awarded without equations.</em></p>
<div class="marks">[2]</div>
<div class="question_part_label">f.</div>
</div>
<br><hr><br><div class="specification">
<p>An equilibrium exists between nitrosyl chloride, NOCl, nitrogen oxide, NO, and chlorine, \({\text{C}}{{\text{l}}_{\text{2}}}\).</p>
<p>\[{\text{2NOCl(g)}} \rightleftharpoons {\text{2NO(g)}} + {\text{C}}{{\text{l}}_2}{\text{(g)}}\]</p>
</div>
<div class="specification">
<p>\({\text{20.0 c}}{{\text{m}}^{\text{3}}}\) of hexane, \({{\text{C}}_{\text{6}}}{{\text{H}}_{{\text{14}}}}\), and \({\text{20.0 c}}{{\text{m}}^{\text{3}}}\) of pentan-1-ol, \({{\text{C}}_{\text{5}}}{{\text{H}}_{{\text{11}}}}{\text{OH}}\), were placed separately into two closed containers at 298 K and allowed to reach equilibrium.</p>
</div>
<div class="specification">
<p>Ammonia is a weak base.</p>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p>(i) Deduce the equilibrium constant expression for this reaction.</p>
<p> </p>
<p> </p>
<p>(ii) Explain the effect on the position of equilibrium and the value of \({K_{\text{c}}}\) when pressure is decreased and temperature is kept constant.</p>
<p> </p>
<p> </p>
<p> </p>
<p> </p>
<p>(iii) 2.00 mol of NOCl was placed in a \({\text{1.00 d}}{{\text{m}}^{\text{3}}}\) container and allowed to reach equilibrium at 298 K. At equilibrium, 0.200 mol of NO was present. Determine the equilibrium concentrations of NOCl and \({\text{C}}{{\text{l}}_{\text{2}}}\), and hence calculate the value of \({K_{\text{c}}}\) at this temperature.</p>
<p> </p>
<p> </p>
<p> </p>
<p> </p>
<p> </p>
<p> </p>
<p>(iv) The value of \({K_{\text{c}}}\) is \(1.60 \times {10^{ - 5}}\) at 318 K. State and explain whether the forward reaction is exothermic or endothermic.</p>
<div class="marks">[7]</div>
<div class="question_part_label">a.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p>(i) Compare the two liquids in terms of their boiling points, enthalpies of vaporization and vapour pressures.</p>
<p> </p>
<p> </p>
<p> </p>
<p> </p>
<p>(ii) Explain your answer given for part (b)(i).</p>
<div class="marks">[4]</div>
<div class="question_part_label">b.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p>Calculate the pH of a \({\text{1.50 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) solution of ammonia at 298 K to two decimal places, using Table 15 of the Data Booklet.</p>
<div class="marks">[2]</div>
<div class="question_part_label">c.i.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p>A buffer solution is made using \({\text{25.0 c}}{{\text{m}}^{\text{3}}}\) of \({\text{0.500 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) hydrochloric acid, HCl (aq), and \({\text{20.0 c}}{{\text{m}}^{\text{3}}}\) of \({\text{1.50 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) ammonia solution, \({\text{N}}{{\text{H}}_{\text{3}}}{\text{(aq)}}\).</p>
<p>Describe the meaning of the term <em>buffer solution</em>.</p>
<div class="marks">[2]</div>
<div class="question_part_label">c.ii.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p>Determine the pH of the buffer solution at 298 K.</p>
<div class="marks">[4]</div>
<div class="question_part_label">c.iii.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p>A \({\text{1.50 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) solution of ammonia is added to \({\text{25.0 c}}{{\text{m}}^{\text{3}}}\) of a \({\text{0.500 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) hydrochloric acid solution in a titration experiment.</p>
<p>Calculate the total volume of the solution at the equivalence point.</p>
<div class="marks">[1]</div>
<div class="question_part_label">c.iv.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p>Calculate the pH of the solution at the equivalence point, using Table 15 of the Data Booklet.</p>
<div class="marks">[4]</div>
<div class="question_part_label">c.v.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p>Identify a suitable indicator for this titration, using Table 16 of the Data Booklet.</p>
<div class="marks">[1]</div>
<div class="question_part_label">c.vi.</div>
</div>
<br><hr><br><div class="specification">
<p class="p1">A buffer solution with a pH of 3.87 contains \({\text{7.41 g}}\,{\text{d}}{{\text{m}}^{ - 3}}\) of propanoic acid, \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{COOH}}\), together with an unknown quantity of sodium propanoate, \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{COONa}}\).</p>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Define the term <em>buffer solution</em>.</p>
<div class="marks">[2]</div>
<div class="question_part_label">a.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Explain, using appropriate equations, how this solution acts as a buffer solution.</p>
<div class="marks">[2]</div>
<div class="question_part_label">b.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Calculate the concentration, in \({\text{mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\), of sodium propanoate in this buffer solution.</p>
<p class="p1">The \({\text{p}}{K_{\text{a}}}\) of propanoic acid is 4.87 at 298 K.</p>
<div class="marks">[4]</div>
<div class="question_part_label">c.</div>
</div>
<br><hr><br><div class="specification">
<p class="p1">Buffer solutions are widely used in both chemical and biochemical systems.</p>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Describe the composition of an acidic buffer solution.</p>
<div class="marks">[1]</div>
<div class="question_part_label">a.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Determine the pH of a buffer solution, correct to <strong>two </strong>decimal places, showing your working, consisting of 10.0 g of \({\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}\) and 10.0 g of CH\(_3\)COONa in \({\text{0.250 d}}{{\text{m}}^{\text{3}}}\) of solution. \({K_{\text{a}}}\) for \({\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}} = 1.8 \times {10^{ - 5}}\) at 298 K.</p>
<div class="marks">[5]</div>
<div class="question_part_label">b.</div>
</div>
<br><hr><br><div class="specification">
<p class="p1">Water is an important substance that is abundant on the Earth’s surface.</p>
</div>
<div class="specification">
<p class="p1">Buffer solutions resist small changes in pH. A phosphate buffer can be made by dissolving \({\text{Na}}{{\text{H}}_{\text{2}}}{\text{P}}{{\text{O}}_{\text{4}}}\) and \({\text{N}}{{\text{a}}_{\text{2}}}{\text{HP}}{{\text{O}}_{\text{4}}}\) in water, in which \({\text{Na}}{{\text{H}}_{\text{2}}}{\text{P}}{{\text{O}}_{\text{4}}}\) produces the acidic ion and \({\text{N}}{{\text{a}}_{\text{2}}}{\text{HP}}{{\text{O}}_{\text{4}}}\) produces the conjugate base ion.</p>
</div>
<div class="specification">
<p class="p1">A \({\text{0.10 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) ammonia solution is placed in a flask and titrated with a \({\text{0.10 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) hydrochloric acid solution.</p>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">(i) <span class="Apple-converted-space"> </span>State the expression for the ionic product constant of water, \({K_{\text{w}}}\).</p>
<p class="p1">(ii) <span class="Apple-converted-space"> </span>Explain why even a very acidic aqueous solution still has some \({\text{O}}{{\text{H}}^ - }\) ions present in it.</p>
<p class="p1">(iii) <span class="Apple-converted-space"> </span>State and explain the effect of increasing temperature on the value of \({K_{\text{w}}}\) given that the ionization of water is an endothermic process.</p>
<p class="p1">(iv) <span class="Apple-converted-space"> </span>State and explain the effect of increasing temperature on the pH of water.</p>
<div class="marks">[7]</div>
<div class="question_part_label">a.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">(i) <span class="Apple-converted-space"> </span>Deduce the acid and conjugate base ions that make up the phosphate buffer and state the ionic equation that represents the phosphate buffer.</p>
<p class="p1">(ii) <span class="Apple-converted-space"> </span>Describe how the phosphate buffer minimizes the effect of the addition of a</p>
<p class="p1">strong base, \({\text{O}}{{\text{H}}^ - }{\text{(aq)}}\), to the buffer. Illustrate your answer with an ionic equation.</p>
<p class="p1">(iii) <span class="Apple-converted-space"> </span>Describe how the phosphate buffer minimizes the effect of the addition of a</p>
<p class="p1">strong acid, \({{\text{H}}^ + }{\text{(aq)}}\), to the buffer. Illustrate your answer with an ionic equation.</p>
<div class="marks">[7]</div>
<div class="question_part_label">b.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">(i) <span class="Apple-converted-space"> </span>Explain why the pH of the ammonia solution is less than 13.</p>
<p class="p1">(ii) <span class="Apple-converted-space"> </span>Estimate the pH at the equivalence point for the titration of hydrochloric acid with ammonia and explain your reasoning.</p>
<p class="p1">(iii) <span class="Apple-converted-space"> </span>State the equation for the reaction of ammonia with water and write the \({K_{\text{b}}}\) expression for \({\text{N}}{{\text{H}}_{\text{3}}}{\text{(aq)}}\).</p>
<p class="p1">(iv) <span class="Apple-converted-space"> </span>When half the ammonia has been neutralized (the half-equivalence point), the pH of the solution is 9.25. Deduce the relationship between \({\text{[N}}{{\text{H}}_{\text{3}}}{\text{]}}\) and \({\text{[NH}}_4^ + {\text{]}}\) at the</p>
<p class="p1">half-equivalence point.</p>
<p class="p1">(v) <span class="Apple-converted-space"> </span>Determine \({\text{p}}{K_{\text{b}}}\) and \({K_{\text{b}}}\) for ammonia based on the pH at the half-equivalence point.</p>
<p class="p1">(vi) <span class="Apple-converted-space"> </span>Describe the significance of the half-equivalence point in terms of its effectiveness as a buffer.</p>
<div class="marks">[11]</div>
<div class="question_part_label">c.</div>
</div>
<br><hr><br><div class="specification">
<p class="p1">Acids can be described as strong or weak.</p>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">(i) <span class="Apple-converted-space"> </span>Outline the difference in dissociation between strong and weak acids of the same concentration.</p>
<p class="p2"> </p>
<p class="p2"> </p>
<p class="p3"><span class="s1">(ii) <span class="Apple-converted-space"> </span></span>Describe <strong>three </strong>tests that can be carried out in the laboratory, and the expected results, to distinguish between \({\text{0.10 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}{\text{ HCl(aq)}}\) and \({\text{0.10 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}{\text{ C}}{{\text{H}}_{\text{3}}}{\text{COOH(aq)}}\).</p>
<div class="marks">[4]</div>
<div class="question_part_label">a.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Calculate the pH, using table 15 of the data booklet, of a solution of ethanoic acid made by dissolving 1.40 g of the acid in distilled water to make a \({\text{500 c}}{{\text{m}}^{\text{3}}}\) solution.</p>
<div class="marks">[4]</div>
<div class="question_part_label">b.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Determine the pH at the equivalence point of the titration and the \({\text{p}}{K_{\text{a}}}\) of an unknown acid using the acid-base titration curve below.</p>
<p class="p1" style="text-align: center;"><img src="images/Schermafbeelding_2016-08-03_om_08.33.12.png" alt="M15/4/CHEMI/HP2/ENG/TZ1/08.c.i"></p>
<div class="marks">[3]</div>
<div class="question_part_label">c.i.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Identify, using table 16 of the data booklet, a suitable indicator to show the end-point of this titration.</p>
<div class="marks">[1]</div>
<div class="question_part_label">c.ii.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Describe how an indicator, that is a weak acid, works. Use Le Chatelier’s principle in your answer.</p>
<div class="marks">[2]</div>
<div class="question_part_label">c.iii.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">State the formula of the conjugate base of chloroethanoic acid, \({\text{C}}{{\text{H}}_{\text{2}}}{\text{ClCOOH}}\).</p>
<div class="marks">[1]</div>
<div class="question_part_label">d.i.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Identify, with a reason, whether chloroethanoic acid is weaker or stronger than ethanoic acid using table 15 of the data booklet.</p>
<div class="marks">[1]</div>
<div class="question_part_label">d.ii.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Determine the pH of the solution resulting when \({\text{100 c}}{{\text{m}}^{\text{3}}}\) of \({\text{0.50 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) \({\text{C}}{{\text{H}}_{\text{2}}}{\text{ClCOOH}}\) is mixed with \({\text{200 c}}{{\text{m}}^{\text{3}}}\) of \({\text{0.10 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) NaOH.</p>
<div class="marks">[4]</div>
<div class="question_part_label">d.iii.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">Describe how chlorine’s position in the periodic table is related to its electron arrangement.</p>
<div class="marks">[2]</div>
<div class="question_part_label">e.</div>
</div>
<div class="question" style="padding-left: 20px; padding-right: 20px;">
<p class="p1">\({\text{SC}}{{\text{l}}_{\text{2}}}\) and \({\text{SCl}}{{\text{F}}_{\text{5}}}\) are two sulfur chloride type compounds with sulfur having different oxidation states. Predict the name of the shape, the bond angle and polarity of these molecules.</p>
<div class="marks">[[N/A]]</div>
<div class="question_part_label">f.</div>
</div>
<br><hr><br>