Which gas is given off when dilute hydrochloric acid is added to calcium carbonate?
How will you test the gas? Write the chemical equations for both reactions.

Carbon dioxide is given off when dilute hydrochloric acid is added to calcium carbonate. The equation involved is:
CaCO₃ + HCl → CaCl₂ + H₂O + CO₂↑

Carbon dioxide can be tested by passing it over lime water. Lime water turns milky. The equation involved is:
Ca(OH)₂ + CO₂ → CaCO₃ + H₂O
​Lime Carbon Calcium Water
dioxide carbonate

The calcium carbonate formed in the reaction is white in colour and not much soluble in water. It gives milky appearance and is used as a test for the presence of carbon dioxide.