Question

With respect to large-scale method of obtaining nitric acid, explain the following: [5 MARKS]
(a) Excess air is taken in the reaction.
(b) The gases entering the catalytic chamber must be pure.
(c) The gases must be cooled before entering the oxidation chamber.
(d) In the catalytic chamber, once the reaction starts, the external source of heat is removed.

Answer 1

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

(a) Excess air is taken in the reaction due to the following reasons:
(i) All the steps of the reaction need oxygen.
(ii) All the three reactions are reversible. With an increase in the concentration of the reactants, the forward reaction is favoured. The equilibrium shifts towards the right.
(iii) Only about 21% of air is oxygen.

(b) The gases entering the catalytic chamber must be pure because impurities present may poison the catalyst and it loses its efficiency.

(c) The gases must be cooled before entering the oxidation chamber because low temperature favours the oxidation of nitric oxide to nitrogen dioxide.

(d) The reaction is exothermic itself, i.e. accompanied by the release of heat, therefore the external source of heat is removed once the reaction starts.