Question

The standard electrode potentials of metals A, B, C and D are $-3.05\,\mathrm{V}$, $-1.66\,\mathrm{V}$, $-0.40\,\mathrm{V}$ and $+0.8\,\mathrm{V}$ respectively. Which of the following would have the highest reducing power?

• A. A
• B. B
• C. C
• D. D

Hint:

Remember: Most negative $E^\circ$ = strongest \textbf{reducing} agent; most positive $E^\circ$ = strongest \textbf{oxidizing} agent.

Answer 1

The Correct Option is A

Step 1: Recall rule.
More negative standard reduction potential ($E^\circ$) $\Rightarrow$ stronger reducing agent (greater tendency to be oxidized).
Step 2: Compare values.
$E^\circ(\text{A})=-3.05$ V < $E^\circ(\text{B})=-1.66$ V < $E^\circ(\text{C})=-0.40$ V < $E^\circ(\text{D})=+0.8$ V.
Thus, A is the most negative and hence the strongest reducing agent.
Step 3: Conclusion.
Metal A has the highest reducing power.