Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!

Did you know?

We also have Bitesize study guides covering many subjects at National 4 and National 5 on our Knowledge & Learning BETA website.

Home > Chemistry > Acids > Reactions of acids


Reactions of acids


In this Revision Bite you will revise some important information about the reactions of acids.

What happens in a neutralisation reaction (General)

Neutralisation is the reaction of acids with neutralisers eg. alkalis [alkali: A base which is soluble in water.

In a neutralisation reaction the pH of the acid moves up towards 7. If an alkali is being used as the neutraliser its pH moves down towards 7.

In this video, an acid with a pH of 4 and an alkali with a pH of 11 are used to neutralise each other. This forms a solution with a pH of 7.

Video clip: Neutral solutions

In order to see this content you need to have both Javascript enabled and Flash installed.


An overly acidic stomach may require neutralisation as shown in this clip.

Video clip: Neutralising the stomach

In order to see this content you need to have both Javascript enabled and Flash installed.


New substances called SALTS and water are formed in neutralisation reactions. The name of the salt that is produced depends on the type of acid and the type of neutraliser being used.

The reaction of hydrogen [hydrogen: diatomic gas that can be detected by a burning splint 'popping'. ions H+ (aq) to form water is an example of neutralisation.

Example question

Here is a typical Standard Grade question. Use the information above to help you answer it. Look at the answer after you have tried to do it.


a) Explain what is meant by a neutralisation reaction.

b) What happens to the pH of an acid as it is neutralised?

c) What happens to the pH of an alkali as it is neutralised?


a) Neutralisation is the reaction of an acid with neutralisers such as alkalis, carbonates and metal oxides, which produces water and a salt.

b) The pH of an acid increases towards 7 in a neutralisation reaction.

c) The pH of an alkali decreases towards 7 in a neutralisation reaction.




Class Clips

Take a look at the effect of pH on food.


PH indicator

Class Clips

Why is it important to know why certain substances are acidic, neutral, or alkaline? Watch to find out.

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.