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Apparatus and chemicals

• Test-tubes (x2)
• Measuring cylinder (10 cm³)
• Universal indicator or pH meter
• Ethanoic acid 0.1 mol/dm³
• Hydrochloric acid 0.1 mol/dm³

Method

1. Using a measuring cylinder, measure 5 cm³ of hydrochloric acid and add to a test-tube.
2. Repeat step 1 with ethanoic acid into a separate test-tube.
3. Add 5 drops of Universal Indicator to each test-tube and record the pH, or use a pH meter to record the pH.

You should find that hydrochloric acid has a lower pH than ethanoic acid.

This tells us that the hydrochloric acid released more H⁺ ions than the ethanoic acid, even though they are both the same concentration.

We can say that ethanoic acid is a weaker acid than hydrochloric acid as it only partly ionises in water. Hydrochloric acid is a strong acid and completely ionises in water.