Which are definitions of an acid according to the Brønsted-Lowry and Lewis theories?

A

Which statement is incorrect for a 0.10 mol dm^–3 HCOOH solution?

A. pH = 1

B. [H⁺] << 0.10 mol dm^–3

C. [HCOO^–] is approximately equal to [H⁺]

D. HCOOH is partially ionized

A

Which species behave as Brønsted-Lowry acids in the following reversible reaction?

\[{{\text{H}}_2}{\text{PO}}_4^ - ({\text{aq)}} + {\text{C}}{{\text{N}}^ - }({\text{aq)}} \rightleftharpoons {\text{HCN(aq)}} + {\text{HPO}}_4^{2 - }({\text{aq)}}\]

A.     HCN and \({\text{C}}{{\text{N}}^ - }\)

B.     HCN and \({\text{HPO}}_4^{2 - }\)

C.     \({{\text{H}}_{\text{2}}}{\text{PO}}_4^ - \) and \({\text{HPO}}_4^{2 - }\)

D.     HCN and \({{\text{H}}_{\text{2}}}{\text{PO}}_4^ - \)

D

Which row correctly describes \({\text{1.0 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}{\text{ NaOH(aq)}}\)?

A

There was concern expressed that we expect candidates to know the colours of universal indicator by rote learning. Far from it, we would expect candidates to have absorbed this information during regular lab classes and demonstrations.

What is the formula of the conjugate base of the hydrogenphosphate ion, \({\rm{HPO}}_4^{2 - }\)?

A.     \({{\text{H}}_{\text{2}}}{\text{PO}}_4^ - \)

B.     \({{\text{H}}_{\text{3}}}{\text{P}}{{\text{O}}_{\text{4}}}\)

C.     \({\text{HPO}}_4^ - \)

D.     \({\text{PO}}_4^{3 - }\)

D

Consider the equilibrium below.

\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{COOH(aq)}} + {{\text{H}}_{\text{2}}}{\text{O(l)}} \rightleftharpoons {\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{CO}}{{\text{O}}^ - }{\text{(aq)}} + {{\text{H}}_{\text{3}}}{{\text{O}}^ + }{\text{(aq)}}\]

Which species represent a conjugate acid-base pair?

A.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{COOH}}\) and \({{\text{H}}_{\text{2}}}{\text{O}}\)

B.     \({{\text{H}}_{\text{2}}}{\text{O}}\) and \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{CO}}{{\text{O}}^ - }\)

C.     \({{\text{H}}_{\text{3}}}{{\text{O}}^ + }\) and \({{\text{H}}_{\text{2}}}{\text{O}}\)

D.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{CO}}{{\text{O}}^ - }\) and \({{\text{H}}_{\text{3}}}{{\text{O}}^ + }\)

C

What will happen if the pressure is increased in the following reaction mixture at equilibrium?

CO₂ (g) + H₂O (l) \( \rightleftharpoons \) H⁺ (aq) + HCO₃⁻ (aq)

A. The equilibrium will shift to the right and pH will decrease.

B. The equilibrium will shift to the right and pH will increase.

C. The equilibrium will shift to the left and pH will increase.

D. The equilibrium will shift to the left and pH will decrease.

A

Activity series of selected elements:

\[{\text{greatest activity}}\xleftarrow{{{\text{K, Ca, Al, Fe, H, Cu, Ag, Au}}}}{\text{least activity}}\]

Which react with dilute sulfuric acid?

       I.     Cu

       II.     CuO

       III.     CuCO₃

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

C

A student carried out a titration to determine the concentration of an acid and found that his value had good precision but poor accuracy. Which process explains this outcome?

A. Consistently overshooting the volume of solution from the burette into the flask.

B. Collection of insufficient titration data.

C. Reading the meniscus in the burette at a different angle each time.

D. Forgetting to rinse the flask after one of the titrations.

A

Three aqueous solutions of nitric acid are listed below.

W.     \({\text{0.100 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}{\text{ HN}}{{\text{O}}_{\text{3}}}{\text{(aq)}}\)

X.     \({\text{0.001 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}{\text{ HN}}{{\text{O}}_{\text{3}}}{\text{(aq)}}\)

Y.     \({\text{0.010 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}{\text{ HN}}{{\text{O}}_{\text{3}}}{\text{(aq)}}\)

What is the correct order of increasing pH of these solutions?

A.     \({\text{W}} < {\text{X}} < {\text{Y}}\)

B.     \({\text{W}} < {\text{Y}} < {\text{X}}\)

C.     \({\text{X}} < {\text{W}} < {\text{Y}}\)

D.     \({\text{X}} < {\text{Y}} < {\text{W}}\)

B

Which pH value is that of an aqueous solution of carbon dioxide?

A.     2.1

B.     5.6

C.     9.8

D.     12.2

B

Which is an acid-base conjugate pair?

A.     H₃O⁺ / OH^–

B.     H₂SO₄ / SO₄^2–

C.     CH₃COOH / H₃O⁺

D.     CH₃NH₃⁺ / CH₃NH₂

D

Which statement is correct?

A.     A strong acid is a good proton donor and has a strong conjugate base.

B.     A weak acid is a poor proton acceptor and has a strong conjugate base.

C.     A strong acid is a good proton donor and has a weak conjugate base.

D.     A strong base is a good proton donor and has a weak conjugate acid.

C

When equal volumes of four \({\text{0.1 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) solutions are arranged in order of increasing pH (lowest pH first), what is the correct order?

A.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}} < {\text{HN}}{{\text{O}}_{\text{3}}} < {\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{N}}{{\text{H}}_{\text{2}}} < {\text{KOH}}\)

B.     \({\text{HN}}{{\text{O}}_{\text{3}}} < {\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}} < {\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{N}}{{\text{H}}_{\text{2}}} < {\text{KOH}}\)

C.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{N}}{{\text{H}}_{\text{2}}} < {\text{HN}}{{\text{O}}_{\text{3}}} < {\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}} < {\text{KOH}}\)

D.     \({\text{KOH}} < {\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{N}}{{\text{H}}_{\text{2}}} < {\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}} < {\text{HN}}{{\text{O}}_{\text{3}}}\)

B

What is the pH of the solution formed when \({\text{10 c}}{{\text{m}}^{\text{3}}}\) of HCl(aq) with pH 1.0 is added to \({\text{990 c}}{{\text{m}}^{\text{3}}}\) of water?

A.     1.5

B.     2.0

C.     2.5

D.     3.0

D

Which are acid-base pairs according to the Brønsted‒Lowry theory?

I.     \({\text{HN}}{{\text{O}}_{\text{3}}}{\text{/NO}}_{\text{3}}^ - \)

II.     \({{\text{H}}_{\text{3}}}{{\text{O}}^ + }{\text{/O}}{{\text{H}}^ - }\)

III.     \({\text{HCOOH/HCO}}{{\text{O}}^ - }\)

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

B

The pH of a solution changes from \({\text{pH}} = 2\) to \({\text{pH}} = 5\). What happens to the concentration of the hydrogen ions during this pH change?

A.     It decreases by a factor of 1000

B.     It increases by a factor of 1000

C.     It decreases by a factor of 100

D.     It increases by a factor of 100

A

What is the Brønsted–Lowry conjugate base of \({{\text{H}}_{\text{2}}}{\text{PO}}_4^ - \)?

A.     \({{\text{H}}_{\text{3}}}{\text{P}}{{\text{O}}_{\text{4}}}\)

B.     \({\text{HPO}}_4^{2 - }\)

C.     \({\text{PO}}_4^{3 - }\)

D.     \({\text{H}}{{\text{O}}^ - }\)

B

10.0 cm³ of an aqueous solution of sodium hydroxide of pH = 10 is mixed with 990.0 cm³ of distilled water. What is the pH of the resulting solution?

A. 8

B. 9

C. 11

D. 12

A

Which of the following is correct?

A.     A weak acid is a proton donor and its aqueous solution shows good conductivity.

B.     A weak acid is a proton donor and its aqueous solution shows poor conductivity.

C.     A weak acid is a proton acceptor and its aqueous solution shows good conductivity.

D.     A weak acid is a proton acceptor and its aqueous solution shows poor conductivity.

B

A student adds 0.3 g of magnesium metal to equal volumes of hydrochloric acid and ethanoic acid of the same concentrations in separate flasks. Which statement is correct?

A.     Hydrochloric acid reacts more rapidly as it has a higher pH than ethanoic acid.

B.     A greater total volume of \({{\text{H}}_{\text{2}}}\) gas is produced with hydrochloric acid than with ethanoic acid.

C.     The same total volume of \({{\text{H}}_{\text{2}}}\) gas is produced with both hydrochloric acid and ethanoic acid.

D.     Ethanoic acid reacts more slowly because it has a lower pH than hydrochloric acid.

C

Opinion was fairly evenly divided between answers B and C (correct).

What is the conjugate base of \({{\text{H}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}\) according to the Brønsted-Lowry theory?

A.     \({\text{CO}}_{\text{3}}^{{\text{2}} - }\)

B.     \({\text{HCO}}_{\text{3}}^ - \)

C.     \({{\text{H}}_{\text{3}}}{\text{CO}}_{\text{3}}^ + \)

D.     \({\text{C}}{{\text{O}}_{\text{2}}}\)

B

Which products would be formed when hydrochloric acid reacts with magnesium oxide?

A.     magnesium chloride and carbon dioxide

B.     magnesium chloride, hydrogen gas and water

C.     magnesium, hydrogen gas and water

D.     magnesium chloride and water

D

A solution of acid A has a pH of 1 and a solution of acid B has a pH of 2. Which statement must be correct?

A.     Acid A is stronger than acid B.

B.     \({\text{[A]}} > {\text{[B]}}\).

C.     The concentration of \({{\text{H}}^ + }\) ions in A is higher than in B.

D.     The concentration of \({{\text{H}}^ + }\) ions in B is twice the concentration of \({{\text{H}}^ + }\) ions in A.

C

Which gas in the atmosphere causes the pH of unpolluted rain to be approximately 6?

A.     Carbon dioxide

B.     Sulfur dioxide

C.     Oxygen

D.     Nitrogen

A

Students found this question to be difficult with 38.16% correct answers; about 28% of students chose either C (oxygen) or D (nitrogen). Presence of \({\text{C}}{{\text{O}}_{\text{2}}}\) in the air causes pH of unpolluted rain water to be approximately 6 in many parts of the world.

What are the conjugate acid–base pairs in the following reaction?

\[{\text{HCO}}_3^ - {\text{(aq)}} + {{\text{H}}_2}{\text{O(l)}} \rightleftharpoons {\text{O}}{{\text{H}}^ - }{\text{(aq)}} + {{\text{H}}_2}{\text{C}}{{\text{O}}_3}{\text{(aq)}}\]

C

Which of the following are weak acids in aqueous solution?

I.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}\)

II.     \({{\text{H}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}\)

III.     HCl

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

A

Which list contains only strong bases?

A.     ammonia, sodium hydroxide, ethylamine

B.     potassium hydroxide, ammonia, sodium hydroxide

C.     lithium hydroxide, potassium hydroxide, barium hydroxide

D.     ammonia, ethylamine, barium hydroxide

C

\({\text{10.0 c}}{{\text{m}}^{\text{3}}}\) of a solution of a strong acid with a pH of 3 is added to a volumetric flask and the total volume is made up to \({\text{1.00 d}}{{\text{m}}^{\text{3}}}\) by adding distilled water. The resulting solution is then thoroughly mixed.

What is the pH of the diluted solution?

A.     1

B.     2

C.     4

D.     5

D

A solution of acid HX has a pH = 1 and a solution of acid HY has a pH = 3. Which statement must be correct?

A.     HX is a stronger acid than HY.

B.     HY is a stronger acid than HX.

C.     The \({\text{[}}{{\text{H}}^ + }{\text{]}}\) in the solution of HX is 100 times greater than the \({\text{[}}{{\text{H}}^ + }{\text{]}}\) in the solution of HY.

D.     The \({\text{[}}{{\text{H}}^ + }{\text{]}}\) in the solution of HY is 100 times greater than the \({\text{[}}{{\text{H}}^ + }{\text{]}}\) in the solution of HX.

C

Which compound reacts with calcium oxide, CaO?

A.     \({{\text{K}}_{\text{2}}}{\text{O}}\)

B.     \({\text{N}}{{\text{a}}_{\text{2}}}{\text{O}}\)

C.     \({\text{S}}{{\text{O}}_{\text{2}}}\)

D.     MgO

C

This question assumed an understanding of Periodicity (3.3.2) and Acid-Base (8.2.1). The majority of candidates (69%) had no difficulty in determining that calcium oxide is a basic oxide and choosing the only acidic oxide, sulfur dioxide, as the answer.

Which 1.0 mol\(\,\)dm^–3 solution has the highest pH?

A.     Ammonium chloride

B.     Sulfuric acid

C.     Sodium chloride

D.     Ammonia

D

Which is not a conjugate acid-base pair?

A.     \({\text{HN}}{{\text{O}}_{\text{3}}}\) and \({\text{NO}}_3^ - \)

B.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}\) and \({\text{C}}{{\text{H}}_{\text{3}}}{\text{CO}}{{\text{O}}^ - }\)

C.     \({{\text{H}}_{\text{3}}}{{\text{O}}^ + }\) and \({\text{O}}{{\text{H}}^ - }\)

D.     \({\text{HSO}}_4^ - \) and \({\text{SO}}_{{\text{42}}}^{2 - }\)

C

Which group of three compounds contains only weak acids and bases?

B

Which compound is a strong acid?

A.     \({\text{N}}{{\text{H}}_{\text{3}}}\)

B.     \({\text{HN}}{{\text{O}}_{\text{3}}}\)

C.     \({{\text{H}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}\)

D.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}\)

B

What occurs when solid sodium hydrogen carbonate reacts with aqueous sulfuric acid? 

A. Bubbles of sulfur dioxide form. 

B. Bubbles of both hydrogen and carbon dioxide form. 

C. Bubbles of hydrogen form. 

D. Bubbles of carbon dioxide form.

D

A solution of \({\text{50 c}}{{\text{m}}^{\text{3}}}\) hydrochloric acid has a pH of 4. What is the final pH if \({\text{450 c}}{{\text{m}}^{\text{3}}}\) of water is added?

A.     3

B.     4

C.     5

D.     6

C

What are the products of the reaction between sulfuric acid and sodium hydrogen carbonate?

A.     NaSO₄ + H₂O + CO₂

B.     Na₂SO₄ + CO₂

C.     Na₂SO₄ + H₂O + CO₂

D.     NaSO₄ + H₂CO₃

C

An example of a strong acid solution is perchloric acid, \({\text{HCl}}{{\text{O}}_{\text{4}}}\), in water. Which statement is correct for this solution?

A.     \({\text{HCl}}{{\text{O}}_{\text{4}}}\) is completely dissociated in the solution.

B.     \({\text{HCl}}{{\text{O}}_{\text{4}}}\) exists mainly as molecules in the solution.

C.     The solution reacts only with strong bases.

D.     The solution has a pH value greater than 7.

A

C

Which \({\text{0.10 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) solution would have the highest conductivity?

A.     HCl

B.     \({\text{N}}{{\text{H}}_{\text{3}}}\)

C.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}\)

D.     \({{\text{H}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}\)

A

Which list contains only strong acids?

A.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH, }}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}{\text{, }}{{\text{H}}_{\text{3}}}{\text{P}}{{\text{O}}_{\text{4}}}\)

B.     \({\text{HCl, HN}}{{\text{O}}_{\text{3}}}{\text{, }}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}\)

C.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH, HN}}{{\text{O}}_{\text{3}}}{\text{, }}{{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}\)

D.     \({\text{HCl, HN}}{{\text{O}}_{\text{3}}}{\text{, }}{{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}\)

D

For equal volumes of \({\text{1.0 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) solutions of hydrochloric acid, HCl(aq), and methanoic acid, HCOOH(aq), which statements are correct?

I.     HCl dissociates more than HCOOH

II.     HCl is a better electrical conductor than HCOOH

III.     HCl will neutralize more NaOH than HCOOH

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

A

With a difficulty index of 24%, this was the second most challenging question on the paper and the responses seem to indicate that the vast majority of candidates think that a strong acid requires more moles of alkali for neutralization than a weak acid. Surprisingly the question proved quite a weak discriminator, with a discrimination index of only 0.15.

Which of the following gases does not result in acid deposition?

A.  CO₂
B.  NO₂
C.  NO
D.  SO₂

A

Which classification is correct for the reaction?

H₂PO₄⁻(aq) + H₂O(l) → HPO₄²⁻(aq) + H₃O⁺(aq)

D

Which descriptions are correct for both a Brønsted–Lowry acid and a Lewis acid?

B

Which species behave as Brønsted–Lowry bases in the following reaction? 

H₂SO₄ + HNO₃  H₂NO₃⁺ + HSO₄^- 

A. HNO₃ and HSO₄^- 

B. HNO₃ and H₂NO₃⁺ 

C. H₂SO₄ and HSO₄^- 

D. H₂NO₃⁺ and HSO₄^-

A