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Question #44760

Difficulty: 8/10 | 🟢 Free

The Question

A galvanic concentration cell at 298 K298\text{ K} is constructed as follows:

\ceAg(s)∣Ag+(aq,C1)∣∣Ag+(aq,C2)∣Ag(s)\ce{Ag(s) | Ag+(aq, C_1) || Ag+(aq, C_2) | Ag(s)}

The concentrations C1C_1 and C2C_2 are determined by the following kinetic data:

  1. A bimolecular elementary reaction has a pre-exponential factor A=6.022×109 L mol−1 s−1A = 6.022 \times 10^9\text{ L mol}^{-1}\text{ s}^{-1} and an activation energy Ea=0E_a = 0. The concentration C1C_1 is numerically equal to its rate constant when expressed in units of cm3 molecule−1 s−1\text{cm}^3\text{ molecule}^{-1}\text{ s}^{-1}.
  2. A separate reaction follows nthn^{\text{th}} order kinetics. Let kLk_L be its rate constant in units of (mol L−1)1−n s−1(\text{mol L}^{-1})^{1-n}\text{ s}^{-1} and kCk_C be its rate constant in units of (mol cm−3)1−n s−1(\text{mol cm}^{-3})^{1-n}\text{ s}^{-1}. Given the ratio kL/kC=10−6k_L / k_C = 10^{-6}, the concentration C2C_2 is numerically equal to 10−n M10^{-n}\text{ M}.

Given NA=6.022×1023 mol−1N_A = 6.022 \times 10^{23}\text{ mol}^{-1} and 2.303RTF=0.059 V\frac{2.303 RT}{F} = 0.059\text{ V} at 298 K298\text{ K}, calculate the electromotive force (EcellE_{\text{cell}}) of the cell.

Options

  • A.

    0.472 V

  • B.

    0.826 V

  • C.

    0.708 V

  • D.

    0.531 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

Concentration Cells|Units of Rate Constant (k)|Collision Frequency vs. Effective Collisions|Electrode Potential Dependencies

Why This Question Is Tricky

Common Mistakes

This problem tests the intersection of electrochemistry and chemical kinetics through rigorous dimensional analysis.

The primary trap lies in converting macroscopic rate constant units (L/mol/s) to microscopic collision frequency units (cm^3/molecule/s), requiring correct application of Avogadro's number and volume conversions (students often divide by 10^3 instead of multiplying).

A secondary trap involves deriving the reaction order from the ratio of rate constants in different concentration units, testing the general unit formula (mol/L)^(1-n) s^-1.

Failing to account for the (1-n) exponent correctly leads to incorrect reaction orders and subsequently wrong cell potentials.

Quick Facts About This Question

Question Information

SubjectChemistry
ChapterElectrochemistry - Class 12
ConceptConcentration Cells
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree