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The following pages consider three well-known types of reactions of acids, which can produce a variety of different salts. The neutralisation reaction of an acid with an alkali has already been illustrated (on the previous page).

Consider how a solid base behaves with an acid.

Similar to an alkali, a base reacts with an acid to give water and a salt.

A salt is produced, but which one?

base + acid _↓ a salt + water

As an example, zinc oxide is a solid base and it reacts with hydrochloric acid.

What is the word equation for this reaction? Which salt is produced? (Hint: think about what's left when the oxygen of the oxide and the hydrogen ions of the acid are used up producing water.)

zinc oxide + hydrochloric acid _↓ zinc chloride + water

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Word equations have been used to describe the above reactions. Why use word equations?

Word equations provide a simple way of describing chemical reactions. They can help to identify trends in reactions and, therefore, help to make predictions about other reactions. Rather than students thinking that they have to learn every single combination of reactions, they can see the broad trends in reactions and apply their thinking skills to specific, unseen examples effectively.

When will an acid not react with a base?

If the salt that is produced is insoluble, it will form a layer round the base and prevent the base from reacting.