Awater insoluble substance "X" on reacting with dilute H2SO4 released a colourless and odourless gas accompanied by a brisk effervescence. WHen the gas was passed through water, the solution turned blue litmus red. On bubbling the gas through lie water the soution became milky and milkyness disappeared when the gas was passed in excess. Identify the substance "X". Write its chemical equations of the reactions involved .

The water insoluble substance ‘X’ is metal carbonate CaCO3. On reacting with dilute H2SO4 released a colourless and odourless gas accompanied by a brisk effervescence which is carbon dioxide.

CaCO3 (s) + H2SO4 (aq) ---------> CaSO4(aq) + H2O (aq) + CO2 (g)

On passing carbon dioxide through water it forms carbonic acid which turns blue litmus red.

CO2 + H2O ---------> H2CO3

  Carbonic acid

On bubbling theCO2 gas through lie water (calcium hydroxide) the solution became milky and milkiness disappeared when the CO2 gas was passed in excess.

Ca(OH)2 + CO2 (g)----------------->CaCO3 (s) + H2O (l)

   (milky)

CaCO3 (s) + CO2 (G)+ H2O (aq)--------------> Ca(OH)2

  Excess CO2   (milkiness disappeared)