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Question #44737

Difficulty: 8/10 | 🟢 Free

The Question

Consider the following electrochemical cell operating in a mixed aqueous-organic solvent at 298 K298 \text{ K}:

\ceZn(s)∣ZnSO4(0.1M)∣∣CuSO4(0.1M)∣Cu(s)\ce{Zn(s) | ZnSO4 (0.1 M) || CuSO4 (0.1 M) | Cu(s)}

Due to the lower dielectric constant of the solvent, significant ion-pairing occurs, preventing complete dissociation. The observed Van't Hoff factors (ii) for the 0.1 M0.1 \text{ M} \ceZnSO4\ce{ZnSO4} and 0.1 M0.1 \text{ M} \ceCuSO4\ce{CuSO4} solutions are 1.401.40 and 1.041.04, respectively.

Given standard reduction potentials: E\ceZn2+/Zn∘=−0.76 VE^\circ_{\ce{Zn^{2+}/Zn}} = -0.76 \text{ V} and E\ceCu2+/Cu∘=+0.34 VE^\circ_{\ce{Cu^{2+}/Cu}} = +0.34 \text{ V}.

Assume the activity coefficients of the free, un-paired ions are unity, and that ion-pairing is the sole reason for the deviation of ii from the ideal stoichiometric value. (Take 2.303RTF=0.06 V\frac{2.303 RT}{F} = 0.06 \text{ V})

What is the cell potential, EcellE_{\text{cell}}?

Options

  • A.

    1.07 V1.07 \text{ V}

  • B.

    1.10 V1.10 \text{ V}

  • C.

    1.13 V1.13 \text{ V}

  • D.

    1.04 V1.04 \text{ V}

Check Your Answer

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

Standard Electrode Potential Sign Conventions|Van’t Hoff Factor (i) Application|Reaction Progress Coordinate

Why This Question Is Tricky

Common Mistakes

This problem tests the deep-structure thermodynamic accuracy of the Nernst equation.

Students frequently fall into the trap of using the analytical (stoichiometric) concentration (0.1 M0.1 \text{ M}) directly in the reaction quotient QQ, which incorrectly yields E=1.10 VE = 1.10 \text{ V} (Option B).

The 'Hidden Variable' is the non-ideal behavior caused by ion-pairing.

By providing the Van't Hoff factor, the student is required to extract the degree of dissociation (α\alpha) to find the true activity of the free electroactive ions.

Another common trap is multiplying the concentration directly by ii instead of α\alpha, or inverting the anode/cathode ratio in the log term (Option C).

Quick Facts About This Question

Question Information

SubjectChemistry
ChapterElectrochemistry - Class 12
ConceptStandard Electrode Potential Sign Conventions
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree