Test for Carbonates (Oxford AQA IGCSE Combined Science Double Award)

Test for Carbonates

• 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 as CO₂ gas is produced, 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 

Testing for carbonate ions