Question

The standard reduction potentials at 298 K for the following half-cell reactions are given:

$Z{n}^{2+}\left(aq\right)+2e^{-}\rightleftharpoons Zn\left(s\right);$ $-0.762V$
$C{r}^{3+}\left(aq\right)+3e^{-}\rightleftharpoons Cr\left(s\right);$ $-0.74V$
$2H^{+}\left(aq\right)+2e^{-}\rightleftharpoons H_2\left(g\right);$ $+0.00V$
$F{e}^{3+}\left(aq\right)+e^{-}\rightleftharpoons F{e}^{2+}\left(aq\right);$ $+0.77V$

Which one of the following is the strongest reducing agent?

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

Answer 1

The correct option is A $Zn\left(s\right)$

The electrode having higher oxidation potential will be stronger reducing agent than electrode having a lower oxidation potential. Hence electrode having higher oxidation potential always undergoes oxidation during the reaction.

The electrode having lowest reduction potential will be the strongest reducing agent than electrode having lower reduction potential. Hence electrode having higher reduction potential always undergoes reduction during the reaction.

So from the given options the reaction:

$Z{n}^{2+}\left(aq\right)+2e^{-}\rightleftharpoons Zn\left(s\right);-0.762$

$Zn\left(s\right)$ is the strongest reducing agent.
Option A is correct.