All carbonates and hydrogen.carbonates react
with dilute acids to liberate carbon dioxide gas.
The reaction is always accompanied by vigorous
bubbling of gas or effervescence. A delivery tube
is used to pass the carbon dioxide gas produced
into limewater. Carbon dioxide forms a white precipitate
CaCO3 (s) + 2HCl -----> CaCl2 (aq) + CO2 (g) + H2O (l)
The nitrates of metals from calcium to copper
in the reactivity series of metals decompose on
strong heating to their respective metal oxides,
oxygen and nitrogen dioxide gas. The pungent brown
gas evolved confirms the presence of a nitrate.
CaCO3 (s) -----> CaO (s) + CO2 (g)