Rahul was given iron filings and sulphur powder. He prepared a compound of iron sulphide by heating the components in a china dish. What would be his observation if he adds a few drops of dilute sulphuric acid into the compound?

A gas with a rotten egg smell is evolved

Explanation:

When iron fillings and sulphur were heated in the vessel, the following chemical reaction took place;

Fe(s) + S(s) > FeS(s)

This is a direct combination reaction.

Subsequently, when dilute H2SO4 is added, the following reaction takes place;

FeS(s) + H2SO4(aq) > FeSO4(aq) + H2S(g)

He immediately observes the evolution of a gas with a rotten egg smell.