Question

Two salts A and B, are given to you with the observations given in the table below. How will you proceed with the identification of the anions present in it? Write in a schematic way.

	Experiment	Observation	Inference
A		A gas with the smell of rotten eggs is evolved.
B		A gas is evolved with a suffocating smell of burning sulphur.

Answer 1

Salt A:

• Experiment: Treat salt A with dilute hydrochloric acid (HCl) or dilute sulphuric acid (H₂SO₄).
• Observation: A gas with the smell of rotten eggs is evolved.
• Inference: Presence of sulphide ion (S²⁻), indicating the salt is a metal sulphide (e.g., FeS or ZnS).
• Reaction: \[\ce{FeS + 2HCl -> FeCl2 + H2S ^}\]

Salt B:

• Experiment: Treat salt B with dilute hydrochloric acid (HCl) or dilute sulphuric acid (H₂SO₄).
• Observation: A gas is evolved with a suffocating smell of burning sulphur.
• Inference: Presence of sulphite ion \[\ce{(SO^{2-}3)}\], indicating the salt is a metal sulphite (e.g., Na₂SO₃).
• Reaction: \[\ce{Na2SO3 + H2SO4 -> Na2SO4 + H2O + SO ^}\]