JEE Main · 2019 · Shift-IImediumEC-087

Given the equilibrium constant KC of the reaction: {Cu(s) + 2Ag^+(aq) Cu^{2+}(aq) + 2Ag(s)} is 10 1015, calculate the…

Electrochemistry · Class 12 · JEE Main Previous Year Question

Question

Given the equilibrium constant KCK_C of the reaction: Cu(s)+2Ag+(aq)Cu2+(aq)+2Ag(s)\mathrm{Cu(s) + 2Ag^+(aq) \rightarrow Cu^{2+}(aq) + 2Ag(s)} is 10×101510 \times 10^{15}, calculate the E°cellE°_{\text{cell}} of this reaction at 298 K.

[2.303RTF at 298 K=0.059 V]\left[2.303\frac{RT}{F}\text{ at }298\ \mathrm{K} = 0.059\ \mathrm{V}\right]

Options
  1. a

    0.04736 mV

  2. b

    0.4736 mV

  3. c

    0.4736 V

  4. d

    0.04736 V

Correct Answerc

0.4736 V

Detailed Solution

Strategy: Use the Nernst-derived relation logK=(nE)/0.059log K = (n \cdot E^\circ) / 0.059 at equilibrium. First, balan\ce the reaction to find the number of electrons transferred (nn).

Step 1: Balan\ce reaction and find nn Reaction: \ceCu(s)+2Ag+(aq)Cu2+(aq)+2Ag(s)\ce{Cu(s) + 2Ag^+(aq) \rightarrow Cu^{2+}(aq) + 2Ag(s)}

  • Cu is oxidized: \ceCuCu2++2e\ce{Cu \rightarrow Cu^{2+} + 2e^-}
  • Ag is redu\ced: \ce2Ag++2e2Ag\ce{2Ag^+ + 2e^- \rightarrow 2Ag} Total n=2n = 2.

Step 2: Calculate EE^\circ K=10×1015=1016K = 10 \times 10^{15} = 10^{16}. logK=16log K = 16 16=2×E0.05916 = \frac{2 \times E^\circ}{0.059} E=16×0.0592=8×0.059=0.472 VE^\circ = \frac{16 \times 0.059}{2} = 8 \times 0.059 = 0.472 \text{ V}

Comparing with options, 0.4736 V0.4736 \text{ V} is the closest (often using slightly different constants like 0.05920.0592).

Answer: (c) 0.4736 V\boxed{\text{Answer: (c) 0.4736 V}}

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