Question

The equivalent mass of $KI{O}_3$ in the reaction $2Cr{\left(OH\right)}_3+O{H}^{-}+KI{O}_3⟶2Cr{O}_4^{2-}+KI+5H_{2}O$ is :

• A. $M$
• B. $\frac{M}{3}$
• C. $\frac{M}{6}$
• D. $\frac{M}{2}$

Answer 1

Answer: (C)

$\frac{M}{6}$

The balanced chemical reaction is $2Cr{\left(OH\right)}_3+O{H}^{-}+KI{O}_3⟶2Cr{O}_4^{2-}+KI+5H_{2}O$.
The oxidation number of iodine changes from +5 to -1.
The change in the oxidation number is 6.
The equivalent mass of potassium iodate is $\frac{\text{Molar mass of potassium iodate}}{\text{Change in the oxidation number of iodine}}=\frac{253.34}{3}=84.44$.