Chemistry - Salt Analysis Question with Solution | TestHub

X salt gives SO₂ on heating with dilute HCl and also sulfur on acidification, so it is thiosulphate (S₂O₃²⁻).

Hence, X = Na₂S₂O₃.

On boiling with sulfur, it forms a modified thiosulphate/polythionate type solution.

With KI₃, it becomes colorless due to the redox reaction of thiosulphate.

With FeCl₃, thiosulphate forms a violet-colored complex with Fe³⁺.

The correct complex formed is ferric–thiosulphate complex $[Fe(S_2{O}_3{)}_6{]}^{3-}$.

* Therefore, the correct identification is Na₂S₂O₃ and $[Fe(S_2{O}_3{)}_6{]}^{3-}$ (Option B).