Question 1

The standard reaction Gibbs energy for the redox process
MnO4-(aq) + NO(g) ⇌ MnO2(s) + NO3-(aq)
Is -206 kJ mol-1. Calculate the standard cell potential.

Accepted Answer

A)  +2.135 V 
B)  +1.068 V 
C)  +0.712 V 
D)  +0.427 V 
A)  +2.135 V 
B)  +1.068 V 
C)  +0.712 V 
D)  +0.427 V

Question 2

The value of the equilibrium constant for the gas-phase reaction
2 NOCl(g) ∏ 2 NO(g) + Cl2(g)
Is K = 7.65 F1F1F1S1F1F1F10 10-8 at 298.15 K. Determine the value of the equilibrium constant expressed in terms of concentrations, Kc, at this temperature.

Accepted Answer

A)  7.65 F1F1F1S1F1F1F10 10-8 
B)  3.10 F1F1F1S1F1F1F10 10-9 
C)  1.90 F1F1F1S1F1F1F10 10-6 
D)  1.25 F1F1F1S1F1F1F10 10-10 
A)  7.65 F1F1F1S1F1F1F10 10-8 
B)  3.10 F1F1F1S1F1F1F10 10-9 
C)  1.90 F1F1F1S1F1F1F10 10-6 
D)  1.25 F1F1F1S1F1F1F10 10-10

Question 3

Calculate the limiting molar conductivity of an aqueous solution of sodium phosphate, Na3PO4, given that the ionic conductivities of the sodium, Na+, and phosphate, PO43-, ions are 5.01 and 24.0 mS m2 mol-1 respectively.

Accepted Answer

A)  29.0 mS m2 mol-1 
B)  77.0 mS m2 mol-1 
C)  39.0 mS m2 mol-1 
D)  19.0 mS m2 mol-1 
A)  29.0 mS m2 mol-1 
B)  77.0 mS m2 mol-1 
C)  39.0 mS m2 mol-1 
D)  19.0 mS m2 mol-1

Question 4

The value of the equilibrium constant for the electrochemical reaction
MnO4-(aq) + 2 H+(aq) + ½ Cl2(g) ∏ Mn2+(aq) + ClO3-(aq) + H2O(aq)
Is 5.88 F1F1F1S1F1F1F10 10-5. What is the value of the equilibrium constant for the reverse reaction?

Accepted Answer

A)  5.88 F1F1F1S1F1F1F10 10-5 
B)  -5.88 F1F1F1S1F1F1F10 10-5 
C)  17.0 F1F1F1S1F1F1F10 103 
D)  -1.70 F1F1F1S1F1F1F10 103 
A)  5.88 F1F1F1S1F1F1F10 10-5 
B)  -5.88 F1F1F1S1F1F1F10 10-5 
C)  17.0 F1F1F1S1F1F1F10 103 
D)  -1.70 F1F1F1S1F1F1F10 103

Question 5

The standard Gibbs energy of reaction for the equilibrium
2 NO2(g) ∏ N2O4(g)
Is -4.73 kJ mol-1 at 298 K. Calculate the value of the equilibrium constant at this temperature.

Accepted Answer

A)  1.00 
B)  6.75 
C)  0.15 
D)  81 
A)  1.00 
B)  6.75 
C)  0.15 
D)  81

Question 6

When an excess of copper (II) iodate, Cu(IO3)2, is added to water at 298 K, the equilibrium concentration of copper ions is 3.27 F1F1F1S1F1F1F10 10-3 mol dm-3. Determine the solubility constant at this temperature.

Accepted Answer

A)  3.27 F1F1F1S1F1F1F10 10-3 
B)  1.40 F1F1F1S1F1F1F10 10-7 
C)  1.07 F1F1F1S1F1F1F10 10-5 
D)  3.50 F1F1F1S1F1F1F10 10-8 
A)  3.27 F1F1F1S1F1F1F10 10-3 
B)  1.40 F1F1F1S1F1F1F10 10-7 
C)  1.07 F1F1F1S1F1F1F10 10-5 
D)  3.50 F1F1F1S1F1F1F10 10-8

Question 7

When lead (II) oxide, PbO, is allowed to react with oxygen, O2, at a temperature of 823 K and standard pressure through the reaction
PbO(s) + ½O2(g) ∏ PbO2(s)
The partial pressure of oxygen at equilibrium is 11.6 Pa. Determine the standard Gibbs energy of reaction at this temperature.

Accepted Answer

A)  -31.0 kJ mol-1 
B)  62.0 kJ mol-1 
C)  -20.8 kJ mol-1 
D)  -41.4 kJ mol-1 
A)  -31.0 kJ mol-1 
B)  62.0 kJ mol-1 
C)  -20.8 kJ mol-1 
D)  -41.4 kJ mol-1

Question 8

The standard cell potential for the reaction
Sn2+(aq) + 2 Cr3+(aq) ⇌ Sn4+(aq) + 2 Cr2+(aq)
Is -0.260 V at 298 K. Calculate the standard Gibbs energy of reaction at this temperature.

Accepted Answer

A)  +25.1 kJ mol-1 
B)  +50.2 kJ mol-1 
C)  -50.1 kJ mol-1 
D)  -25.1 kJ mol-1 
A)  +25.1 kJ mol-1 
B)  +50.2 kJ mol-1 
C)  -50.1 kJ mol-1 
D)  -25.1 kJ mol-1

Question 9

Calculate the standard reaction Gibbs energy for the reaction
2 N2O5(g) 4 NO2(g) + O2(g) at a temperature of 298 K. The standard Gibbs energies of formation of the components at this temperature are given in the table below.
$\begin{array}{lc}
& \Delta \mathrm{f} G^{e}(298 \mathrm{~K}) / \mathrm{kJ} \mathrm{mol}^{-1} \
\mathrm{N}_{2} \mathrm{O}_{5} \
& +118.0 \
\mathrm{NO}_{2} \
& +51.8\
\mathrm{O}_{2}\
&0\
\end{array}$

Accepted Answer

A)  -66.2 kJ mol-1 
B)  -89.2 kJ mol-1 
C)  -28.8 kJ mol-1 
D)  -169.8 kJ mol-1 
A)  -66.2 kJ mol-1 
B)  -89.2 kJ mol-1 
C)  -28.8 kJ mol-1 
D)  -169.8 kJ mol-1

Question 10

Determine the pH of an aqueous solution of benzoic acid, C6H5COOH, of concentration 0.064 mol dm-3. The pKa of benzoic acid is 4.19.

Accepted Answer

A)  4.19 
B)  1.50 
C)  2.69 
D)  2.10 
A)  4.19 
B)  1.50 
C)  2.69 
D)  2.10

The standard reaction Gibbs energy for the redox process MnO₄^-(aq) + NO(g) ⇌ MnO₂(s) + NO₃^-(aq) Is -206 kJ mol^-1. Calculate the standard cell potential.

The value of the equilibrium constant for the gas-phase reaction 2 NOCl(g) ∏ 2 NO(g) + Cl₂(g) Is K = 7.65  10^-8 at 298.15 K. Determine the value of the equilibrium constant expressed in terms of concentrations, K_c, at this temperature.

Calculate the limiting molar conductivity of an aqueous solution of sodium phosphate, Na₃PO₄, given that the ionic conductivities of the sodium, Na⁺, and phosphate, PO₄^3-, ions are 5.01 and 24.0 mS m² mol^-¹ respectively.

The value of the equilibrium constant for the electrochemical reaction MnO₄^-(aq) + 2 H⁺(aq) + ½ Cl₂(g) ∏ Mn²⁺(aq) + ClO₃^-(aq) + H₂O(aq) Is 5.88  10^-5. What is the value of the equilibrium constant for the reverse reaction?

The standard Gibbs energy of reaction for the equilibrium 2 NO₂(g) ∏ N₂O₄(g) Is -4.73 kJ mol^-1 at 298 K. Calculate the value of the equilibrium constant at this temperature.

When an excess of copper (II) iodate, Cu(IO₃)₂, is added to water at 298 K, the equilibrium concentration of copper ions is 3.27  10^-3 mol dm^-3. Determine the solubility constant at this temperature.

When lead (II) oxide, PbO, is allowed to react with oxygen, O₂, at a temperature of 823 K and standard pressure through the reaction PbO(s) + ½O₂(g) ∏ PbO₂(s) The partial pressure of oxygen at equilibrium is 11.6 Pa. Determine the standard Gibbs energy of reaction at this temperature.

The standard cell potential for the reaction Sn²⁺(aq) + 2 Cr³⁺(aq) ⇌ Sn⁴⁺(aq) + 2 Cr²⁺(aq) Is -0.260 V at 298 K. Calculate the standard Gibbs energy of reaction at this temperature.

Calculate the standard reaction Gibbs energy for the reaction 2 N₂O₅(g) 4 NO₂(g) + O₂(g) at a temperature of 298 K. The standard Gibbs energies of formation of the components at this temperature are given in the table below. \Delta(298)/ +118.0 +51.8 0

Determine the pH of an aqueous solution of benzoic acid, C₆H₅COOH, of concentration 0.064 mol dm^-3. The pK_a of benzoic acid is 4.19.

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Exam 5: Chemical Change

The standard reaction Gibbs energy for the redox process MnO4-(aq) + NO(g) ⇌ MnO2(s) + NO3-(aq) Is -206 kJ mol-1. Calculate the standard cell potential.

The value of the equilibrium constant for the gas-phase reaction 2 NOCl(g) ∏ 2 NO(g) + Cl2(g) Is K = 7.65  10-8 at 298.15 K. Determine the value of the equilibrium constant expressed in terms of concentrations, Kc, at this temperature.