Question

Standard potential of electrode reaction \(\mathrm{Cu}_{(\mathrm{aq})}^{+2}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Cu}_{(\mathrm{s})}\) is +0.34 V .

What is standard potential of reaction

\[ 2 \mathrm{Cu}_{(\mathrm{s})} \longrightarrow 2 \mathrm{Cu}_{(\mathrm{aq})}^{+2}+4 \mathrm{e}^{-} ? \]

• A. +0.68 V
• B. -0.68 V
• C. +0.34 V
• D. -0.34 V

Hint:

Reversing a reaction changes the sign of the standard potential, and multiplying by a number does not change it.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
Standard electrode potential is an intensive property.
It does not change when the equation is multiplied by a coefficient, but it changes sign when the reaction is reversed.

Step 2: Given reaction
\(\text{Cu}^{2+}+2e^{-}\rightarrow \text{Cu}\) has \(E^{\circ}=+0.34\) V.

Step 3: Calculation
The required reaction \(2\text{Cu}\rightarrow 2\text{Cu}^{2+}+4e^{-}\) is the reverse of the given reaction multiplied by 2.
Reversal gives \(-0.34\) V and the factor 2 does not change it, so \(E^{\circ}=-0.34\) V.

Final Answer:
The standard potential of the oxidation reaction is \(-0.34\) V. \[ \boxed{\text{(D) }-0.34\text{ V}} \]