Question

Balance the following reaction.

$As{H}_3+KCl{O}_3\to H_{3}As{O}_4+KCl$

• A. $3As{H}_3+4KCl{O}_3\to 3H_{3}As{O}_4+4KCl$
• B. $As{H}_3+5KCl{O}_3\to 5H_{3}As{O}_4+2KCl$
• C. $3As{H}_3+3KCl{O}_3\to 5H_{3}As{O}_4+4KCl$
• D. None of these

Answer 1

The correct option is A $3As{H}_3+4KCl{O}_3\to 3H_{3}As{O}_4+4KCl$

The unbalanced redox equation is as follows:

$As{H}_3+KCl{O}_3\to H_{3}As{O}_4+KCl$

All atoms other than $H$ and $O$ are balanced.

The oxidation number of $As$ changes from +3 to +5. The change in the oxidation number of $As$ is 2.

The oxidation number of $Cl$ changes from +5 to -1. The change in the oxidation number of $Cl$ is 6.

The increase in the oxidation number is balanced with a decrease in the oxidation number by multiplying $As{H}_3$ and $H_{3}As{O}_4$ with 3.

$3As{H}_3+KCl{O}_3\to 3H_{3}As{O}_4+KCl$

$O$ atoms are balanced.

$3As{H}_3+4KCl{O}_3\to 3H_{3}As{O}_4+4KCl$

This is the balanced chemical equation.