a) 1 Mark
b) 2 Marks
c) 2 Marks
(a) When nitric acid is added to KI (aq.), it is oxidised to iodine.
6KI+8HNO3→6KNO3+4H2O+2NO+3I2
(b) When nitric acid is added to washing soda (sodium carbonate), carbon dioxide gas is evolved.
Na2CO3Sodium carbonate+2HNO3→2NaNO3+CO2+H2O
When carbon dioxide gas is passed through freshly prepared lime water (calcium hydroxide), it turns milky due to the formation of calcium carbonate.
Ca(OH)2Limewater+CO2→CaCO3(Milky)+H2O
When the gas is passed in excess, the milkiness disappears due to the formation of soluble calcium bicarbonate.
CaCO3(Milky)+H2O+CO2→Ca(HCO3)2(soluble)
(c) When limestone or calcium carbonate reacts with nitric acid, calcium nitrate is formed with the evolution of carbon dioxide gas.
CaCO3+2HNO3→Ca(NO3)2+CO2↑+H2O