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Question 1

Calculate the ionic strength of a solution of iron (III) carbonate, Fe₂(CO₃)₃ of concentration 0.020 mol dm^-3.

a) 0.25

b) 0.30

c) -0.10

d) 0.00

Question 2

Use the Debye-Hückel limiting law to calculate the mean activity coefficient for the ions in an aqueous solution of potassium sulfate, K₂SO₄, of molality 0.010 mol kg^-1 at 25°C.

a) 0.943

b) 1.074

c) 1.023

d) 0.932

Question 3

The pK_a of hydrocyanic acid, HCN, is 9.218 at 293 K. Calculate the conductivity of an aqueous solution of perchloric acid, of concentration 0.015 mol dm^-3, given that the ionic conductivity of H⁺ ions is 35 mS m² mol^-1 and of CN^- ions is 82 mS m² mol^-1.

a) 12 mS m² mol^-1

b) 24 × 10^-2 mS m² mol^-1

c) 8.1 × 10^-2 mS m² mol^-1

d) 15 × 10^-2 mS m² mol^-1

Question 4

For a galvanic cell, which of the following statements is never true?

a) The potential of the cathode is higher than that of the anode.

b) The electrons flow in the external circuit from the anode to the cathode.

c) Reduction takes place at the cathode.

d) Oxidation takes place at the anode.

Question 5

The standard reaction Gibbs energy for the electrochemical reaction
Cr₂O₇^2- + 2 Fe + 14 H⁺ → 2 Cr³⁺ + 2 Fe³⁺ 7 H₂O
is -793 kJ mol^-1. Calculate the standard cell potential.

a) +1.37 V

b) +4.11 V

c) +2.74 V

d) +2.05 V

Question 6

The standard cell potential for the reaction
2 NO + ½ O₂ + H₂O → 2 HNO₂
was measured to be +0.240 V. Calculate the standard reaction Gibbs energy.

a) -11.6 kJ mol^-1

b) -23.2 kJ mol^-1

c) -46.3 kJ mol^-1

d) -96.5 kJ mol^-1

Question 7

The standard cell potential for the reaction
Cu²⁺(aq) + Fe²⁺(aq) + I^-(aq) ⇌ CuI(s) + Fe³⁺(aq)
is +0.090 V. Use the Nernst equation to calculate the electrochemical potential at 298.15 K for the cell
Pt(s) | CuI₂(aq, 0.010 mol dm^-3) | CuI(s) || FeSO₄(aq, 0.010 mol dm^-3), Fe₂(SO₄)₃(aq, 0.020 mol dm^-3) | Pt(s)

a) -0.147 V

b) -0.129 V

c) -0.309 V

d) +0.090 V

Question 8

Calculate the equilibrium constant for the reaction
S₂O₈^2-(aq) + 2 Fe²⁺(aq) ⇌ 2 Fe³⁺(aq) + 2 SO₄^2-(aq)
at 25.0°C, given that the standard cells potentials for the two half reactions at this temperature are
S₂O₈^2-(aq) + 2 e^- ⇌ 2 SO₄^2-(aq) E° = +2.08 V
Fe³⁺(aq) + e^- ⇌ Fe²⁺(aq) E° = +0.77 V

a) 102

b) 2 × 10⁹⁶

c) 2 × 10⁴⁴

d) 2 × 10⁴8

Question 9

Use the data in Table 9.3 to calculate the standard cell potential for the reaction
Zn(s) | Zn²⁺(aq) || MnO₄^-(aq),Mn²⁺(aq),H⁺(aq) | Pt(s)

a) +2.27 V

b) +0.75 V

c) -0.75 V

d) -2.27 V

Question 10

The standard cell potential for the Daniell cell,
Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)
is +1.102 V at 298 K and +1.095 V at 363 K. Calculate the standard reaction entropy.

a) +20.8 J K^-1 mol^-1

b) -20.8 J K^-1 mol^-1

c) +10.4 J K^-1 mol^-1

d) -10.4 J K^-1 mol^-1

Oxford University Press, Online Resource Centre, Chapter 09.

Chapter 09

Instructions