Electrochemistry Chapter-Wise Test 12

Correct answer Carries: 4.

Wrong Answer Carries: -1.

In a fuel cell using H\(_2\) and O\(_2\), what is the product of the overall reaction?

Reaction: \( 2H_2(g) + O_2(g) \rightarrow 2H_2O(l) \). Product is water.

H\(_2\)
O\(_2\)
H\(_2\)O
OH\(^-\)
3

What is the potential of a hydrogen electrode in a solution with pH = 7 at 298 K? (Given: \( E^\circ_{H^+/H_2} = 0.00 \, V \))

\( E = E^\circ - \frac{0.059}{n} \log \frac{1}{[H^+]} \), \( [H^+] = 10^{-7} \), \( n = 1 \).

\( E = 0 - 0.059 \times 7 = -0.413 \, V \).

0.00 V
-0.295 V
-0.118 V
-0.413 V
4

The limiting molar conductivity of SrCl\(_2\) is 260 S cm\(^2\) mol\(^{-1}\). If \( \lambda^\circ_{Sr^{2+}} = 118 \, S \, cm^2 \, mol^{-1} \), what is \( \lambda^\circ_{Cl^-} \)?

\( \Lambda_m^\circ = \lambda^\circ_{Sr^{2+}} + 2\lambda^\circ_{Cl^-} \).

\( 260 = 118 + 2\lambda^\circ_{Cl^-} \), \( 2\lambda^\circ_{Cl^-} = 142 \), \( \lambda^\circ_{Cl^-} = 71 \, S \, cm^2 \, mol^{-1} \).

71 S cm\(^2\) mol\(^{-1}\)
142 S cm\(^2\) mol\(^{-1}\)
118 S cm\(^2\) mol\(^{-1}\)
260 S cm\(^2\) mol\(^{-1}\)
1

In a lead storage battery, what is the product formed at both electrodes during discharge?

During discharge: Anode: \( Pb + SO_4^{2-} \rightarrow PbSO_4 + 2e^- \), Cathode: \( PbO_2 + SO_4^{2-} + 4H^+ + 2e^- \rightarrow PbSO_4 + 2H_2O \). Product at both is \( PbSO_4 \).

Pb
PbSO\(_4\)
PbO\(_2\)
H\(_2\)SO\(_4\)
2

A cell has \( E^\circ_{cell} = 0.88 \, V \) and \( \Delta_r G^\circ = -169840 \, J/mol \) at 298 K. How many electrons are transferred? (F = 96500 C/mol)

\( \Delta_r G^\circ = -n F E^\circ_{cell} \), \( -169840 = -n \times 96500 \times 0.88 \).

\( n = \frac{169840}{96500 \times 0.88} = \frac{169840}{84920} \approx 2 \).

1
2
3
4
2

How many coulombs are required to deposit 2.07 g of lithium from a LiCl solution? (Atomic mass of Li = 6.9 g/mol, F = 96500 C/mol)

\( Li^+ + e^- \rightarrow Li \). 1 mol Li (6.9 g) requires 1F.

Moles = \( \frac{2.07}{6.9} = 0.3 \, mol \), Charge = \( 0.3 \times 96500 = 28950 \, C \).

28950 C
96500 C
57900 C
14475 C
1

What is the standard cell potential for the galvanic cell where zinc is oxidized and copper ions are reduced, given the standard electrode potentials of Zn\(^{2+}/Zn\) = -0.76 V and Cu\(^{2+}/Cu\) = 0.34 V?

The cell reaction is \( Zn(s) + Cu^{2+}(aq) \rightarrow Zn^{2+}(aq) + Cu(s) \).

\( E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode} = 0.34 - (-0.76) = 1.10 \, V \).

1.10 V
0.42 V
1.52 V
-1.10 V
1

In the electrolysis of aqueous NaCl with inert electrodes, what gas is produced at the anode?

Anode: \( 2Cl^- \rightarrow Cl_2 + 2e^- \). Chlorine gas is produced due to overpotential.

H\(_2\)
O\(_2\)
Cl\(_2\)
N\(_2\)
3

How many coulombs are required to deposit 0.27 g of aluminum from Al(NO\(_3\))\(_3\) solution? (Atomic mass of Al = 27 g/mol, F = 96500 C/mol)

\( Al^{3+} + 3e^- \rightarrow Al \). 1 mol Al (27 g) requires 3F.

Moles = \( \frac{0.27}{27} = 0.01 \, mol \), Charge = \( 0.01 \times 3 \times 96500 = 2895 \, C \).

965 C
1930 C
9650 C
2895 C
4

A cell has \( E^\circ_{cell} = 0.59 \, V \) and an equilibrium constant of \( 10^{20} \) at 298 K. How many electrons are transferred?

\( E^\circ_{cell} = \frac{0.059}{n} \log K_c \), \( 0.59 = \frac{0.059}{n} \times 20 \), \( n = \frac{1.18}{0.59} = 2 \).

1
2
3
4
2

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