$\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3$ reacts with moist $\mathrm{Cl}_2$ to form $\mathrm{Na}_2…
$\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3$ reacts with moist $\mathrm{Cl}_2$ to form $\mathrm{Na}_2 \mathrm{SO}_4, \mathrm{HCl}$ and $X$. Which one of the following is $X$ ?
$\mathrm{H}_2 \mathrm{~S}$
$\mathrm{SO}_2$
$\mathrm{SO}_3$
$\mathrm{S}$
Solution
Sodium thiosulphate is oxidised by moist $\mathrm{Cl}_2$ or chlorine water and precipitates sulphur,
$
\begin{aligned}
& \mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3+\mathrm{Cl}_2+\mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{Na}_2 \mathrm{SO}_4+2 \mathrm{HCl} \\
& \text { sodium } \\
& \text { thiosulphate }
\end{aligned}
$