Question

Identify the gas evolved and give the chemical test in the following case:

Dilute hydrochloric acid reacts with iron (II) sulphide.

Answer 1

Gas Evolved: When dilute hydrochloric acid reacts with iron (II) sulphide, the gas evolved is hydrogen sulphide.

Reaction:

\[\ce{FeS + 2HCl -> FeCl2 + H2S ^}\]

Chemical Test for Hydrogen Sulphide: To test for H₂S gas, you can use lead acetate paper:

1. Moisten a strip of lead acetate paper.
2. Expose it to the gas that evolved.

Observation: If H₂S is present, the lead acetate paper will turn black due to the formation of lead sulphide (PbS).

\[\ce{Pb(C2H3O2)2 + H2S -> PbS + 2CH3COOH}\]