The pH scales measures the acidity or alkalinity of a solution. Acids and bases have a wide variety of uses and can react together in neutralisation reactions.
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 and also carbon dioxide gas.
\[\begin{array}{l} \text{Hyrdrochloric acid} + \text{calcium carbonate} \to \\ \text{calcium chloride} + \text{water} + \text{carbon dioxide} \end{array}\]
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).