Question:medium

\(E_{cell}\), for the cell given below is 0.82 V. What is its \(E^{\circ}\) value? \(Fe | Fe^{2+}(0.001 \text{ M}) || Cu^{2+}(0.1 \text{ M}) | Cu\). (Given: \(\frac{2.303 RT}{F} = 0.06 \text{ V}\))

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Always ensure the value of 'n' matches the number of electrons involved in the balanced redox equation.
Updated On: Jun 9, 2026
  • 0.63 V
  • 0.69 V
  • 0.76 V
  • 0.87 V
Show Solution

The Correct Option is C

Solution and Explanation

Step 1: Recall the Nernst equation.
For a cell at room temperature, $E_{cell} = E^{\circ}_{cell} - \dfrac{0.06}{n}\log Q$, where $n$ is the number of electrons and $Q$ is the reaction quotient. Here we are given $\dfrac{2.303RT}{F} = 0.06$ V.
Step 2: Write the cell reaction and find n.
Iron is the anode and copper is the cathode, so \[ Fe + Cu^{2+} \rightarrow Fe^{2+} + Cu \] Two electrons are transferred, so $n = 2$.
Step 3: Write the reaction quotient Q.
Only ions appear in $Q$, so \[ Q = \frac{[Fe^{2+}]}{[Cu^{2+}]} = \frac{0.001}{0.1} = 10^{-2} \]
Step 4: Plug values into the Nernst equation.
With $\dfrac{0.06}{2} = 0.03$, \[ 0.82 = E^{\circ}_{cell} - 0.03 \log(10^{-2}) \]
Step 5: Evaluate the log term.
Since $\log(10^{-2}) = -2$, the equation becomes \[ 0.82 = E^{\circ}_{cell} - 0.03(-2) = E^{\circ}_{cell} + 0.06 \]
Step 6: Solve for the standard potential.
So $E^{\circ}_{cell} = 0.82 - 0.06 = 0.76$ V.
\[ \boxed{0.76 \text{ V}} \]
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