Question

The following reaction occurs in acidic aqueous solution:
$H_{3}As{O}_4+Zn\to As{H}_3+Z{n}^{2+}$
$H_{3}As{O}_4$ is a ______ agent in which the oxidation number of $As$ is _______ .

• A. $\text{Reducing},+5$
• B. $\text{Oxidizing},+5$
• C. $\text{Reducing},+3$
• D. $\text{Oxidizing},+3$

Answer 1

The correct option is B $\text{Oxidizing},+5$

$H_{3}As{O}_4+Zn\to As{H}_3+Z{n}^{2+}$
Here, $Zn$ is oxidized to $Z{n}^{2+}$.
So, $H_{3}As{O}_4$ is reduced and acts as an oxidising agent.
$\text{In}{H}_{3}As{O}_4$
Let, the oxidation state of $As$ be $x$
$1\times 3+x+(-2\times 4)=0$
$\Rightarrow 3+x-8=0\Rightarrow x=+5$
Hence, oxidation state of $As$ in $H_{3}As{O}_4$ is $+5$.