Question:medium

For the cell,
$\ominus\text{Zn}_{(s)} | \text{Zn}^{+2}(1\text{M}) || \text{Ag}^{+1}(1\text{M}) | \text{Ag}_{(s)}^\oplus$
If concentration of $\text{Zn}^{+2}$ decreases to $0.1\text{ M}$ at $298\text{ K}$, then emf of cell}

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Decreasing product concentration shifts equilibrium forward, increasing cell potential.
Updated On: May 14, 2026
  • increase by $0.0592\text{ V}$
  • decrease by $0.0592\text{ V}$
  • increase by $0.0296\text{ V}$
  • decrease by $0.0296\text{ V}$
Show Solution

The Correct Option is C

Solution and Explanation

Step 1: Understanding the Concept:
The cell potential (EMF) changes with concentration as described by the Nernst Equation.
Step 2: Key Formula or Approach:
$\text{E}_{\text{cell}} = \text{E}^\circ_{\text{cell}} - \frac{0.0592}{\text{n}} \log\left(\frac{[\text{Products}]}{[\text{Reactants}]}\right)$
Cell reaction: $\text{Zn} + 2\text{Ag}^+ \rightarrow \text{Zn}^{2+} + 2\text{Ag}$, where $\text{n}=2$.
Step 3: Detailed Explanation:
Initial state: $[\text{Zn}^{2+}] = 1\text{ M}$, $[\text{Ag}^+] = 1\text{ M} \rightarrow \text{E}_1 = \text{E}^\circ_{\text{cell}}$.
New state: $[\text{Zn}^{2+}] = 0.1\text{ M}$, $[\text{Ag}^+] = 1\text{ M}$.
\[ \text{E}_2 = \text{E}^\circ_{\text{cell}} - \frac{0.0592}{2} \log\left(\frac{0.1}{1^2}\right) \]
\[ \text{E}_2 = \text{E}^\circ_{\text{cell}} - 0.0296 \times \log(10^{-1}) \]
\[ \text{E}_2 = \text{E}^\circ_{\text{cell}} - 0.0296 \times (-1) = \text{E}^\circ_{\text{cell}} + 0.0296\text{ V} \]
$\Delta \text{E} = \text{E}_2 - \text{E}_1 = +0.0296\text{ V}$.
Step 4: Final Answer:
The EMF increases by $0.0296\text{ V}$.
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