Qualitative Analysis of Carbonate Ion
Carbonate ion (CO32–) can be detected by treating a salt with dilute H2SO4.
Observation
Brisk effervescence and a colourless odourless gas is given out.
MCO3 + H2SO4 → MSO4 + H2O + CO2 (carbon dioxide)
Confirmatory Test
On passing the gas through lime water, it turns milky due to the formation of calcium carbonate.
Ca(OH)2 + CO2 → CaCO3 ↓ + H2O
On passing excess of CO2+ the milkiness disappears and a clear solution is obtained.
CaCO3 + CO2 + H2O → Ca(HCO3)2