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Question #44321

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The Question

An electrochemical cell is constructed at 298 K. The anode compartment consists of a Nickel electrode, and the cathode compartment consists of a Copper electrode coated with \ce{CuO(s)}. Both compartments contain a buffer solution of pH = 10 and are connected by a salt bridge. The cell discharges through an external load.

Given at 298 K: $E^\circ_{\ce{Cu^{2+}/Cu}} = +0.34 \text{ V}$ $E^\circ_{\ce{Ni^{2+}/Ni}} = -0.25 \text{ V}$ $K_{sp}(\ce{Cu(OH)_2}) = 10^{-20}$ $K_{sp}(\ce{Ni(OH)_2}) = 10^{-16}$

Assume \ce{CuO(s)} is thermodynamically equivalent to \ce{Cu(OH)_2(s)} in the aqueous medium, and $\frac{2.303RT}{F} = 0.059 \text{ V}$ .

Which of the following represents the maximum dissolved $[\ce{Ni^{2+}}]$ in the anode compartment and the constant cell potential ( $E_{cell}$ ) maintained during the precipitation of \ce{Ni(OH)_2}?

Options

A.
$10^{-8} \text{ M, } 0 \text{ V}$
B.
$10^{-8} \text{ M, } +0.472 \text{ V}$
C.
$10^8 \text{ M, } 0 \text{ V}$
D.
$10^{-16} \text{ M, } +0.236 \text{ V}$

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Numerical_Precision

Improve calculation stamina and avoid rounding errors in high-stakes competitive examinations.

Concepts Behind This Question

Acid-Base Nature of Oxides|Electrode Potential Dependencies|Metal Activity Series Logic

Why This Question Is Tricky

Common Mistakes

Students often assume a galvanic cell discharges until $E_{cell} = 0$ V, calculating $[\ce{Ni^{2+}}]$ by setting the Nernst equation to zero (yielding an absurd $10^8$ M).

This ignores the solubility limit imposed by the basic buffer.

Furthermore, once $\ce{Ni(OH)_2}$ precipitates, the overall cell reaction becomes a solid-state transformation.

Since all species in the new overall reaction are solids or liquids, the reaction quotient $Q = 1$ , locking the cell potential at a constant $+0.472$ V.

The basicity of the buffer modulates the hydroxide activity, stabilizing the metal cation as a precipitate and preventing the cell from reaching equilibrium ( $0$ V).

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Classification of Elements and Periodicity in Properties - Class 11 Part 1
Concept	Acid-Base Nature of Oxides
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free