When sulphur is boiled with $\mathrm{Na}_2 \mathrm{SO}_3$, a compound $(A)$ is produced. $(A)$ on reaction with excess $\mathrm{AgNO}_3$ solution gives a compound $(B)$, which after dissolving in water produces a black coloured sulphide $(C)$. Identify the compound $(A),(B)$ and $(C)$.

• Correct answer
  A

  $\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3, \mathrm{Ag}_2 \mathrm{~S}_2 \mathrm{O}_3, \mathrm{Ag}_2 \mathrm{~S}$
• B

  $\mathrm{Na}_2 \mathrm{SO}_4, \mathrm{Ag}_2 \mathrm{SO}_4, \mathrm{Ag}_2 \mathrm{~S}$
• C

  $\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_7, \mathrm{Ag}_2 \mathrm{SO}_4, \mathrm{Ag}_2 \mathrm{~S}$
• D

  $\mathrm{Na}_2 \mathrm{SO}_5, \mathrm{Ag}_2 \mathrm{SO}_5, \mathrm{Ag}_2 \mathrm{SO}_4$

Solution

When sulphur ( $\mathrm{S}$ ) is heated with $\mathrm{Na}_2 \mathrm{SO}_3$, a compound $\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3(A)$ is produced. When $\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3$ react with excess of $\mathrm{AgNO}_3$ solution, it will give a $\mathrm{Ag}_2 \mathrm{~S}_2 \mathrm{O}_3(B)$ which is a water soluble compound. Further $\mathrm{Ag}_2 \mathrm{~S}_2 \mathrm{O}_3$ dissolves in water, to produce a black coloured sulphide $\mathrm{Ag}_2 \mathrm{~S}(C)$.
Hence, compound $A$ is $\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3, B$ is $\mathrm{Ag}_2 \mathrm{~S}_2 \mathrm{O}_3$ and $C$ is $\mathrm{Ag}_2 \mathrm{~S}$.

Hence, the correct answer is option: 'A'.