Equivalent mass of $\mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3} \cdot 5 \mathrm{H}_{2} \mathrm{O}$ in the…

Equivalent mass of $\mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3} \cdot 5 \mathrm{H}_{2} \mathrm{O}$ in the reaction $2 \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}+\mathrm{I}_{2} ightarrow \mathrm{Na}_{2} \mathrm{~S}_{4} \mathrm{O}_{6}+2 \mathrm{NaI}$ is
  1. $124 \mathrm{~g} \mathrm{eq}^{-1}$
  2. $248 \mathrm{~g} \mathrm{eq}^{-1}$
  3. $84 \mathrm{~g} \mathrm{eq}^{-1}$
  4. $72 \mathrm{~g} \mathrm{eq}^{-1}$

Solution

$2 \mathrm{S}_{2} \mathrm{O}_{3}^{2-} ightarrow \mathrm{S}_{4} \mathrm{O}_{6}^{2-}+2 \mathrm{e}^{-}$
Equivalent mass of $\mathrm{Na}_{2} \mathrm{S}_{2} \mathrm{O}_{3} \cdot 5 \mathrm{H}_{2} \mathrm{O}=\frac{2 \times \mathrm{Molar} \text { mass of } \mathrm{Na}_{2} \mathrm{S}_{2} \mathrm{O}_{3} \cdot 5 \mathrm{H}_{2} \mathrm{O}}{2 \mathrm{~eq} \mathrm{~mol}^{-1}}=248 \mathrm{~g} \mathrm{~eq}^{-1}$

Asked in: JEE-TOPICTESTS-CHEMISTRY

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