Acids, alkalis and neutralisation
Identify the salt and write a reaction that conserves atoms and charge.
What you will learn
- Predict products of acid–alkali reactions.
- Write the ionic neutralisation equation.
Choose the salt from the reactants
An acid reacting with an alkali produces a salt and water. Hydrochloric acid supplies chloride, sulfuric acid supplies sulfate, and nitric acid supplies nitrate. The positive ion usually comes from the alkali.
This pattern is for acid–alkali neutralisation. Other acid reactions differ: acids with reactive metals can release hydrogen, while acids with carbonates release carbon dioxide.
Remove spectator ions
In a strong acid–alkali reaction, hydrogen ions and hydroxide ions form water. Ions unchanged on both sides are spectators and are omitted from the net ionic equation. Check that both atom counts and total charge are balanced.
Worked example
Name the products when nitric acid reacts completely with potassium hydroxide.
Show the worked solution
- Potassium hydroxide provides potassium ions.
- Nitric acid provides nitrate ions, so the salt is potassium nitrate.
- Hydrogen and hydroxide ions form water.
Answer Potassium nitrate and water
Common mistakes
- Neutralisation with an alkali does not normally produce hydrogen gas.
- The name of the acid determines the negative ion in the salt.
What can you explain now?
Write the products of hydrochloric acid reacting with sodium hydroxide.
Compare with the explanation
Sodium chloride and water
The salt combines sodium and chloride; H⁺ and OH⁻ form water.
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