Question

Identify the reaction from following so that the standard potential of \(\text{Cu}^{+2}/\text{Cu}\) electrode is 0.34 V. with respective to SHE ?

• A. \(\text{Cu}\rightarrow \text{Cu}^{+2}+2e^-\)
• B. \(\text{Cu}^{+2}+2e^-\rightarrow \text{Cu}\)
• C. \(\text{Cu}^+\rightarrow \text{Cu}^{+2}+e^-\)
• D. \(\text{Cu}^{+3}\rightarrow \text{Cu}^{+2}+e^-\)

Hint:

Standard electrode potentials are written for reduction half reactions.

Answer 1

The Correct Option is B

Step 1: Convention:
A table of $E^\circ$ lists reductions: oxidised form plus electrons gives reduced form.

Step 2: Match the couple:
The couple $\text{Cu}^{2+}/\text{Cu}$ has $\text{Cu}^{2+}$ as the oxidised form and $\text{Cu}$ as the reduced form, so the reaction is $\text{Cu}^{2+}+2e^-\to\text{Cu}$.

Step 3: Other options:
Option (A) is the oxidation direction and would carry the opposite sign. (C) and (D) belong to other couples. So option (B).

Final Answer:
The reduction half reaction carries 0.34 V. \[ \boxed{\text{(B) }\text{Cu}^{2+}+2e^-\rightarrow\text{Cu}} \]