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

Writing formula equations for neutralisation reactions (General/Credit)


In the exercise in part 3 you had practice writing word equations for neutralisation reactions. Now you will gain some experience of writing formula equations.


Sodium hydroxide + Hydrochloric acid → Sodium chloride + Water

(NaOH + HCl → NaCl + H2O)


Magnesium oxide + Sulphuric acid → Magnesium sulphate + Water

(MgO + H2SO4 → MgSO4 + H2O)


Potassium carbonate + Nitric acid → Potassium nitrate + Water + Carbon dioxide

(K2CO3 + 2HNO3 → 2KNO3 + H2O + CO2)

Example question

Now try writing formula equations for the reactions below.


It is worthwhile learning the formulae of the three acids most commonly used :

  • hydrochloric acid (HCl)
  • sulphuric acid (H2SO4)
  • nitric acid (HNO3)

Use valency [valency: the 'combining power' of atoms or ions to work out the formulae of the neutraliser and the products. The formula for water and the formula for carbon dioxide are easy to remember!

There is no need to balance the equations unless the equation asks you to. This will only happen in a question at Credit level.


Write formula equations for the word equations given below.

potassium hydroxide + nitric acid → potassium nitrate + water

calcium oxide + hydrochloric acid → calcium chloride + water

lithium carbonate + nitric acid → lithium nitrate + water + carbon dioxide


KOH + HNO3 → KNO3 + H2O

CaO + 2HCl → CaCl2 + H2O

Li2CO3 + 2HNO3 → 2LiNO3 + H2O + CO2


At Credit level in Standard Grade you will be expected to balance formula equations.

Example question

Try to balance the formula equations given below.

Hint: Balance the equations by putting balancing numbers in front of formula. Do not change the formula after it has been correctly written.


LiOH + H2SO4 → Li2SO4 + H2O

CuO + HNO3 → Cu(NO3)2 + H2O

CaCO3 + HCl → CaCl2 + H2O + CO2


2LiOH + H2SO4 → Li2SO4 + 2H2O

CuO + 2HNO3 → Cu(NO3)2 + H2O

CaCO3 + 2HCl → CaCl2 + H2O + CO2



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.