Question

What happens when (give balanced equation) [5 MARKS]
(a) Nitric acid is added to KI (aq.)?
(b) Nitric acid is added to washing soda and the resulting gas is passed through a freshly prepared lime water?
(c) Limestone reacts with nitric acid?

Answer 1

a) 1 Mark
b) 2 Marks
c) 2 Marks

(a) When nitric acid is added to KI (aq.), it is oxidised to iodine.
$6KI+8HN{O}_3\to 6KN{O}_3+4H_{2}O+2NO+3I_2$

(b) When nitric acid is added to washing soda (sodium carbonate), carbon dioxide gas is evolved.
$\underset{Sodiumcarbonate}{N{a}_{2}C{O}_3}+2HN{O}_3\to 2NaN{O}_3+C{O}_2+H_{2}O$
When carbon dioxide gas is passed through freshly prepared lime water (calcium hydroxide), it turns milky due to the formation of calcium carbonate.
$\underset{Limewater}{Ca(OH{)}_2}+C{O}_2\to \underset{\left(Milky\right)}{CaC{O}_3}+H_{2}O$
When the gas is passed in excess, the milkiness disappears due to the formation of soluble calcium bicarbonate.
$\underset{\left(Milky\right)}{CaC{O}_3}+H_{2}O+C{O}_2\to \underset{\left(soluble\right)}{Ca(HC{O}_3{)}_2}$

(c) When limestone or calcium carbonate reacts with nitric acid, calcium nitrate is formed with the evolution of carbon dioxide gas.
$CaC{O}_3+2HN{O}_3\to Ca(N{O}_3{)}_2+CO2\uparrow +H_{2}O$