X, the salt formed, is FeCl2.
[1 Mark]
Metal oxides are basic in nature. They react with acids to give salt and water. This kind of reaction is called neutralisation reaction.
In the given reaction, ferrous oxide (FeO) reacts with hydrochloric acid (HCl) to form ferrous chloride salt (FeCl2) along with water (H2O).
The chemical reaction involved is:
FeO(aq) + 2HCl(aq)→FeCl2(aq)+ H2O(l)