Carbonates (AQA GCSE Chemistry)

• Carbonates all contain the carbonate ion, CO₃^2-
• The test for this ion involves adding dilute acid and testing the gas released
• If a carbonate compound is present then effervescence should be seen and the gas produced is CO₂ which forms a white precipitate of calcium carbonate when bubbled through limewater:

CO₃^2- (aq) + 2H⁺ (aq) → CO₂ (g) + H₂O (l)

CO₂ (g) + Ca(OH)₂ (aq) → CaCO₃(s) + H₂O(l)

• The white precipitate turns limewater cloudy 

Test for carbonates 

Limewater turns cloudy in the presence of CO₂