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Question 1

Calculate the concentration of hydronium, H₃O⁺, ions in a solution of with pH = 4.3.

a) 20 × 10³ mol dm^-3

b) 5.0 × 10^-5 mol dm^-3

c) 14 × 10^-3 mol dm^-3

d) 74 mol dm^-3

Question 2

The standard Gibbs energy of reaction, Δ_rG°, for the dissociation of phenol is 56.4 kJ mol^-1 at 298 K. Calculate the pK_a of phenol.

a) 9.88

b) 22.8

c) 4.12

d) 5.24

Question 3

The pK_a of hypochlorous acid, HClO, is 7.53. What is the value of pK_b?

a) 6.47

b) 7.53

c) 5.37 × 10^-4

d) 2.02

Question 4

Calculate the concentration of OH^- ions in a solution with pH = 12.1.

a) 79.4 mol dm^-3

b) 7.94 × 10^-13 mol dm^-3

c) 1.90 mol dm^-3

d) 0.0126 mol dm^-3

Question 5

Calculate the pH of an aqueous solution of hydrocyanic acid of concentration 0.088 mol dm^-3. The acidity constant of hydrocyanic acid is 4.9 × 10^-10.

a) 6.57

b) 8.82

c) 5.18

d) 7.43

Question 6

Calculate the concentration of SO₃^2- ions in an aqueous solution of sulfurous acid, H₂SO₃. The second acidity constant of sulfurous acid is K_a2 = 1.2 × 10^-7.

a) 1.8 × 10^-⁷ mol dm^-3

b) 1.2 × 10^-7 mol dm^-3

c) 6.3 × 10^-¹³ mol dm^-3

d) 7.7 × 10^-⁷ mol dm^-3

Question 7

Calculate the pH of an aqueous solution of potassium hydrogensulfite, KHSO₃. For sulfurous acid, pK_a1 = 1.81 and pK_a2 = 6.91.

a) 3.82

b) 5.10

c) 8.72

d) 4.36

Question 8

In a titration, 2.7 cm³ of 0.100 mol dm^-3 sodium hydroxide, NaOH, solution is added to 25.0 cm³ of 0.125 mol dm^-3 benzoic acid, C₆H₅COOH, solution. Calculate the pH of the resulting solution given that the pK_a of benzoic acid is 4.19.

a) 3.13

b) 5.25

c) 1.74

d) 6.67

Question 9

Use the data in Table 8.1 to estimate the pH of a buffer solution formed from equal amounts of potassium carbonate, K₂CO₃, and potassium hydrogen carbonate, KHCO₃.

a) 7.6

b) 10.3

c) 6.4

d) 3.9

Question 10

Calculate the concentration of chloride ions, Cl^-, in an aqueous solution formed by adding lead chloride, PbCl₂, to water. The solubility constant of lead chloride is 1.6 × 10^-5.

a) 0.025 mol dm^-3

b) 0.004 mol dm^-3

c) 0.032 mol dm^-3

d) 0.050 mol dm^-3

Oxford University Press, Online Resource Centre, Chapter 08.

Chapter 08

Instructions