Acid-Base Reactions
Acids donate hydrogen ions (H⁺) in solution while bases accept them. When acids and bases react they produce a salt and water in a neutralisation reaction.
What You Need to Know
Key Concept Diagram
Acids have pH below 7; bases (alkalis) have pH above 7; neutral solutions have pH = 7
Neutralisation: acid + base → salt + water (e.g. HCl + NaOH → NaCl + H₂O)
Indicators change colour to reveal whether a solution is acidic, neutral, or basic
Strong acids/bases fully dissociate in water; weak acids/bases only partially dissociate
Key Vocabulary
Acid
A substance that donates hydrogen ions (H⁺) in solution and has a pH below 7
Base
A substance that accepts hydrogen ions and has a pH above 7; soluble bases are called alkalis
Neutralisation
The reaction between an acid and a base to form a salt and water
pH scale
A scale from 0 to 14 measuring acidity or alkalinity; 7 is neutral, below 7 is acidic, above 7 is basic
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
What two products are always formed in a neutralisation reaction?
Question 2
A solution has pH = 2. What does this indicate?
Question 3
Which substance acts as a base in this reaction: HCl + NaOH → NaCl + H₂O?
Key Concepts Summary
- ●Acids have pH below 7; bases (alkalis) have pH above 7; neutral solutions have pH = 7
- ●Neutralisation: acid + base → salt + water (e.g. HCl + NaOH → NaCl + H₂O)
- ●Indicators change colour to reveal whether a solution is acidic, neutral, or basic
- ●Strong acids/bases fully dissociate in water; weak acids/bases only partially dissociate