Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
1. Which is a Brønsted - Lowry conjugate acid/ base pair?
A. H3O+ / OH–
B. OH– / O2–
C. H2SO4 / SO42–
D. NH4+ / NH2–
2. Which species act as Brønsted - Lowry acids in the following reactions?
NH2–(aq) + H2O(l) ⇌ NH3(aq) + OH–(aq)
CH3NH2(aq) + H2O(l) ⇌ CH3NH3+ (aq) + OH–(aq)
I. NH3(aq)
II. CH3NH3+ (aq)
III. H2O(l)
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
3. Which equations represent acid-base reactions according to Lewis theory?
I. Fe2+ + 6H2O → [Fe(H2O)6]2+
II. BF3 + F– → BF4–
III. 2H2 + O2 → 2H2O
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
4. Which gives an acidic solution when dissolved in water?
A. CH3COOH
B. CH3CHO
C. CH3CH2OH
D. CH3COCH3
5. Which substance reacts with dilute nitric acid to produce hydrogen gas?
A. FeCO3
B. Fe(OH)3
C. Fe2O3
D. Fe
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
6. Which substance is not a base?
A. CuO
B. NaCl
C. NaHCO3
D. CuCO3
7. Which list contains only strong acids?
A. HCl, HNO3, H2CO3
B. HCl, HNO3, H2SO4
C. CH3COOH, H2CO3, H2SO4
D. H2SO4, CH3COOH, H2CO3
8. Which can be used to distinguish between a solution of a strong monoprotic acid
and a solution of weak monoprotic acid with the same concentration?
I. Add zinc to each solution and measure the rate of formation of gas
produced.
II. Add sodium hydroxide solution to each solution and measure the
temperature change.
III. Measure the pH
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
9. Which will change the pH of a solution from value of 2 to a value of 4?
A. Doubling the concentration of H+(aq).
B. Doubling the concentration of OH-(aq).
C. Decreasing the concentration of H+(aq) by a factor of 100.
D. Decreasing the concentration of OH–(aq) by a factor of 100.
10. Which of the following 0.010 mol dm-3 solutions will have the lowest pH?
A. iodoethanoic acid Ka = 6.60 x 10-4
B. methanoic acid Ka = 1.78 x 10-4
C. chloroethanoic acid Ka = 1.34 x 10-3
D. 2,4-dinitrophenol Ka = 8.5 x 10-5
11. Which is correct concerning the pH and pOH values of an aqueous solution at
298 K?
A. pH + pOH = 1 x 1014
B. pH + pOH = 1 x 10-14
C. pH + pOH = 14
D. pH x pOH = 14
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
12. What will happen to the value of the pH of 1 cm3 of a solution of a strong base
when 999 cm3 of water are added to it?
A. It will decrease by 3
B. It will increase by 3
C. It will decrease by a factor of 3
D. It will increase by a factor of 3
13. Which is the correct order of decreasing acid strength for the following?
2-methylpropanoic acid Ka = 1.45 x 10-5
2,2-dimethylpropanoic acid Ka = 9.33 x 10-6
benzoic acid Ka = 6.31 x 10-5
A. 2,2-dimethylpropanoic acid, benzoic acid, 2-methylpropanoic acid
B. 2,2-dimethylpropanoic acid, 2-methylpropanoic acid, benzoic acid
C. 2-methylpropanoic acid, benzoic acid, 2,2-dimethylpropanoic acid
D. benzoic acid, 2-methylpropanoic acid, 2,2-dimethylpropanoic acid
14. What happens to water ( Kw = 1 x 10-14) when the temperature is raised from
298 K to 308 K?
H2O(l) ⇌ H+(aq) + OH–(aq) ∆HStandard Sign = + 57.6 kJ mol-1
A. [H+] increases and the water stays neutral.
B. [H+] increases and the water becomes acidic.
C. [H+] decreases and the water stays neutral.
D. [H+] decreases and the water becomes basic.
15. What is the Kb expression for the reaction of methylamine with water?
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
16. Which could be used to make a buffer solution?
I. KOH(aq) + CH3COOH(aq)
II. NaCH3COO(aq) + CH3COOH(aq)
III. NH3(aq) + NH4Cl(aq)
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
17. What is the hydroxide ion concentration in a buffer solution in which [NH3] =
2.00 mol dm-3 and [NH4+] = 1.00 mol dm-3? (Kb for NH3 = 1.8 x 10-5)
A. 1.8 x 10-5
B. 3.6 x 10-5
C. 9.0 x 10-4
D. 9.0 x 10-6
18. Which salts dissolves in water to produce a solution with a pH value lower than
7?
I. FeCl3(s)
II. NH4Cl(s)
III. KCN(s)
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
19. Which titration should use phenolphthalein (pKa = 9.50) as an indicator and not
methyl orange (pKa = 3.46)?
A. NaOH(aq) + HCl(aq)
B. CH3COOH(aq) + NH3(aq)
C. HCl(aq) + NH3(aq)
D. NaOH(aq) + CH3COOH(aq)
20. At approximately what pH will an acid base indicator with a pKa value of 5.0
change colour?
A. 3
B. 5
C. 7
D. 9
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
14 Hypochlorous acid, HOCl(aq), is an example of a weak acid.
(a) State the expression for the ionic product constant of water, Kw. (1)
(b) A household bleach contains sodium hypochlorite, NaOCl(aq), at a
concentration of 0.705 mol dm–3. The hypochlorite ion, OCl–(aq), is a weak base.
OCl−(aq) + H2O(l)   HOCl(aq) + OH−(aq)
(i) The pKa value of HOCl(aq) is 7.52. Determine the Kb value of OCl–(aq)
assuming a temperature of 298 K. (1) (ii) Determine the concentration of OH–(aq), in mol dm–3, at equilibrium and state
one assumption made in arriving at your answer other than a temperature of 298
K. (3) (iii) Calculate the pH of bleach (2)
(Total = 7 Marks)
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
14 Hypochlorous acid, HOCl(aq), is an example of a weak acid.
(a) State the expression for the ionic product constant of water, Kw. (1)
(b) A household bleach contains sodium hypochlorite, NaOCl(aq), at a
concentration of 0.705 mol dm–3. The hypochlorite ion, OCl–(aq), is a weak base.
OCl−(aq) + H2O(l)   HOCl(aq) + OH−(aq)
(i) The pKa value of HOCl(aq) is 7.52. Determine the Kb value of OCl–(aq)
assuming a temperature of 298 K. (1)
(ii) Determine the concentration of OH–(aq), in mol dm–3, at equilibrium and state
one assumption made in arriving at your answer other than a temperature of 298
K. (3) .
.
.
.
.
.
.
.
.
.
.
.
.
.
(Total = 7 marks)
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
15 (a) (i) Define the terms acid and base according to the Brønsted–Lowry theory.
Distinguish between a weak base and a strong base. State one example of a weak
base. (3)
(ii) Weak acids in the environment may cause damage. Identify a weak acid in the
environment and outline one of its effects. (2)
(iii) The graph below indicates the pH change during the titration of 20.0 cm3 of
0.100 mol dm–3 of CH3COOH(aq) with 0.100 mol dm–3 KOH(aq). From the
graph, identify the volume of KOH(aq) and the pH at the equivalence point. (2) Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
(iv) Explain how the graph could be used to determine the pKa of ethanoic acid
and determine the pKa value for these data. (2)
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
(v) Sketch a graph, similar to the previous graph, to indicate the change in pH
during a titration of 25.0 cm3 of 0.100 mol dm–3 HNO3(aq) with 0.100 mol dm–3
OH–(aq). On your graph, clearly indicate the starting pH value, the equivalence
point, the pH at the equivalence point, and the final pH reached. (4)
(b) (i)
Describe how an indicator works. (3)
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
(ii) Using Table 16 of the Data Booklet, identify the most appropriate indicator for
the titration of ethanoic acid with potassium hydroxide. Explain your choice. (2)
(Total = 18 marks)
16 Ammonia can be converted into nitric acid (HNO3(aq)) and hydrocyanic acid
(HCN(aq)). The pKa of hydrocyanic acid is 9.21.
(a) Distinguish between the terms strong acid and weak acid and state the
equations used to show the dissociation of each acid in aqueous solution. (3) Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
(b) Deduce the expression for the ionization constant, Ka, of hydrocyanic acid and
calculate its value from the pKa value given. (2) (c) Use your answer from part (b) to calculate the [H+] and the pH of an aqueous
solution of hydrocyanic acid of concentration 0.108 mol dm–3. State one
assumption made in arriving at your answer. (4) (Total = 9 marks) Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
1. B, 2. D, 3. A, 4. A, 5. D, 6. B, 7. B, 8. D, 9. C, 10. C,
11. C, 12. A, 13. D, 14. A, 15. A, 16. D, 17. B, 18. A, 19. D, 20. B.
14 (a) K (b) (i)
(ii)
= [H+][OH–]
pKa(HOCl) = 7.52
OCl– is the conjugate base of HOCl.
pKb(OCl–) = pKw – pKa(HOCl)
= 14.00 – 7.52 = 6.48
Kb(OCl–) = 10–pKb = 10–6.48 = 3.3 × 10–7
Base dissociation reaction for hypochlorite, OCl–, is:
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set
Nomen: _________________________________________
Dies:_______________
IB Chemistry Year 2 HL
Topic 8 and 18 - Unit 8 Acids and Bases – Problem Set