# Neutralisation

The reaction between an acid and an alkali (or base) that makes a salt and water. The pH moves towards 7.

Chemistry (school) · Part 06: Acids, bases and salts · Card 5 of 9 · Last updated 2026-10-19

## Analogy

It is like cooling hot tea by adding cold milk. The two opposites balance each other.

## Example

**Neutralisation**

acid + alkali -> salt + water
HCl + NaOH -> NaCl + H2O
Ionic: H+ + OH- -> H2O

## In practice

Indigestion tablets contain bases that neutralise extra stomach acid.

## Practice

### Flashcards

- **What is made in a neutralisation reaction?** A salt and water.

### Interview questions

**Describe how you would make a pure, dry sample of copper sulfate crystals from copper oxide and sulfuric acid.**

- Warm the acid and add copper oxide until no more dissolves
- Filter off the extra copper oxide
- Heat the filtrate to evaporate some water
- Leave to crystallise, then dry the crystals

## Questions people ask

### What happens to the pH during neutralisation?

The pH moves towards 7. Adding alkali to an acid raises it from below 7. Adding acid to an alkali lowers it from above 7. At the exact end point the solution is neutral. Adding too much of either one pushes the pH past 7 again.

### What is the ionic equation for neutralisation?

H+ + OH- -> H2O. It shows what really happens: hydrogen ions from the acid join with hydroxide ions from the alkali to make water. The other ions, such as sodium and chloride, are spectator ions and stay in solution as the salt.

## Related concepts

- [Salt](https://studyvisually.com/learn/science/chemistry-school/chemistry-school-part-6/chemistry-school-part-6-concept-6)

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