Question

The standard reduction potentials at 298K for the following half cell reaction are given below:

$Z{n}^{2+}\left(aq\right)+2e^{-}\rightleftharpoons Zn\left(s\right);E^o=-0.762V$
$C{r}^{3+}\left(aq\right)+3e^{-}\rightleftharpoons Cr\left(s\right);E^o=+0.762V$
$2H^{+}\left(aq\right)+2e^{-}\rightleftharpoons H_2\left(g\right);E^o=+0.00V$
$F{e}^{3+}\left(aq\right)+e^{-}\rightleftharpoons F{e}^{2+}\left(aq\right);E^o=+0.770V$

Based on the above reactions, select the strongest reducing agent?

• A. $Zn\left(s\right)$
• B. $Cr\left(s\right)$
• C. $H_2\left(g\right)$
• D. $F{e}^{2+}\left(aq\right)$

Answer 1

Answer: (A)

An electrode with low SRP acts as a strong reducing agent. So, the reducing power is maximum for one with maximum oxidation potential.

Oxidation potential of Zn is $0.762$ V, oxidation potential of Cr is $-0.762$ V, oxidation potential of $H_2$ is $0$ V, and oxidation potential of $F{e}^{2+}$ is $-0.770$ V.

$\therefore$ Zn is the strongest reducing agent.

Hence, the correct option is $\text{A}$