Base

An acid can be neutralised by a base. In this topic, the bases include metal oxides, metal hydroxides and metal carbonates. An alkali is simply a base that dissolves in water: sodium hydroxide solution is an alkali, whereas copper oxide is an insoluble base.

Powdered calcium hydroxide and calcium oxide are both bases: they react with the acid. As you add either solid, hydrogen ions are used up, so the pH rises. Near pH 7 the mixture is neutral; adding more base can make it alkaline.

An acid can react with a base to form two products: a salt and water.