Question

In the reaction, $2S_2{O}_3^{2-}+I_2⟶S_4{O}_6^{2-}+2I^{-}$, the equivalent weight of $N{a}_2{S}_2{O}_3$ is equal to its.

• A. Molecular wt.
• B. $\frac{1}{2}\times$ Molecular wt.
• C. $2\times$ Molecular wt.
• D. $\frac{1}{6}\times$ Molecular wt..

Answer 1

Answer: (A)

Molecular wt.

According to reaction,

$2S_2{O}_3^{2-}+I_2\to S_4{O}_6^{2-}+2I^{-}$

Oxidation of $S$ in $S_2{O}_3^{2-}=2$

Oxidation number of $S$ in $S_4{O}_6^{2-}=\frac{5}{2}$

Again, $2S_2{O}_3^{-2}\to S_4{O}_6^{-2}$

For 2 moles of $S_2{O}_3^{-2}$ change in oxidation number

$=4\times \frac{5}{2}-2\times 2\times 2$

$=2$

For 1 mol $=\frac{2}{2}=1$

$\therefore$ Equivalent mass of $N{a}_2{S}_2{O}_3=\frac{\text{Molecular wt}}{\text{Change in oxidation no.}}$

$=\frac{\text{Molecular wt}}{1}$

$\therefore$ option A is correct