Acids are neutralised by bases

A neutralisation reaction is one in which an acid reacts with a base to form water. A salt is also formed in this reaction.

Bases are metal oxides, metal hydroxides and metal carbonates.

In the neutralisation reaction between an acid and a metal carbonate, there are three products:

  • a salt
  • water
  • carbon dioxide gas

There is a general equation for a neutralisation reaction between an acid and a metal carbonate:

\[metal\,carbonate + acid \to salt + water + carbon\,dioxide\]

One example of this is the reaction of hydrochloric acid and calcium chloride.

\[\begin{array}{l} \text{hydrochloric acid} + \text{calcium carbonate} \to \\ \text{calcium chloride} + \text{water} + \text{carbon dioxide} \end{array}\]

\[2HCl + CaCO_3^{} \to CaCl_2^{} + H_2^{}O + CO_2^{}\]

The salt is named in the same way as before, taking the metal's name from the metal carbonate and the ending from the type of acid used.

Carbon dioxide can be tested for using lime water (turns from colourless to chalky white).

Preparing salts from neutralisation reactions

When insoluble metal carbonates and insoluble metal oxides are used to produce soluble salts, excess base is added to the acid.

The mixture can then be filtered to remove unreacted metal carbonate or metal oxide.

The filtrate can then be evaporated to leave the salt produced.

Watch this video of a practical demonstration in which copper carbonate and sulfuric acid react to produce copper sulfate.

Reaction of cooper carbonate and sulfuric acid