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Question #44790

Difficulty: 8/10 | 🟢 Free

The Question

An electrolytic cell is used for the deposition of copper from an aqueous \ce{CuSO4} solution. The cell contains a porous barrier separating two \ce{HCl} solutions with concentrations C1=10−3 mol cm−3C_1 = 10^{-3} \text{ mol cm}^{-3} and C2=1 mol m−3C_2 = 1 \text{ mol m}^{-3}, which creates a Liquid Junction Potential (ELJPE_{LJP}). The transport number of \ce{H+} is 0.800.80.

The applied potential across the cell is Eapp=1.08 VE_{app} = 1.08 \text{ V}. The ELJPE_{LJP} acts as an opposing potential, reducing the effective current efficiency for copper deposition to η=(1−ELJPEapp)×100%\eta = \left(1 - \frac{E_{LJP}}{E_{app}}\right) \times 100\%.

A total charge of 1.93×107 C1.93 \times 10^7 \text{ C} per cubic meter of the cathode compartment volume is passed. The volume of the cathode compartment is 10 L10 \text{ L}. Assuming ideal behavior, calculate the mass of copper deposited at the cathode.

(Given: 2.303RTF=0.06 V\frac{2.303 RT}{F} = 0.06 \text{ V} at 298 K298 \text{ K}, F=96500 C mol−1F = 96500 \text{ C mol}^{-1}, Atomic mass of Cu = 63.5 g mol−163.5 \text{ g mol}^{-1}. The LJP for a single electrolyte is given by ELJP=(t+−t−)2.303RTFlog⁡C1C2E_{LJP} = (t_+ - t_-) \frac{2.303 RT}{F} \log \frac{C_1}{C_2})

Options

  • A.

    57.15 g57.15 \text{ g}

  • B.

    63.50 g63.50 \text{ g}

  • C.

    69.85 g69.85 \text{ g}

  • D.

    114.30 g114.30 \text{ g}

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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

Liquid Junction Potential|Faraday's First and Second Laws|Units of Rate Constant (k)

Why This Question Is Tricky

Common Mistakes

This problem tests the integration of Electrochemistry (Liquid Junction Potential) with Faraday's Laws, while embedding a rigorous unit conversion trap.

Students frequently fail to convert CGS (mol cm−3\text{mol cm}^{-3}) and SI (mol m−3\text{mol m}^{-3}) units to a common molarity base, leading to an inverted concentration ratio.

This inversion produces a negative LJP, artificially inflating the current efficiency above 100%100\% (Option C).

Additionally, failing to account for the valency of Copper (Option D) or ignoring the LJP entirely (Option B) are common pitfalls.

Quick Facts About This Question

Question Information

SubjectChemistry
ChapterElectrochemistry - Class 12
ConceptLiquid Junction Potential
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree