A. further heating
B. adding concentrated H2SO4
C. cooling the acid solution with cold water
D. bubbling air through the acid solution
Correct Answer:
Option D – bubbling air through the acid solution
Explanation
Bubbling of air through the acid solution removes deposited oxides of nitrogen.
Nitric acid is prepared in the laboratory by heating a nitrate salt with the concentrated acid.
NaNO3 + H2SO4 → NaHSO4 + HNO3
Vapours of nitric acid are condensed to a brown liquid in a receiver cooled under cold water. “Dissolved oxides of nitrogen” e.g NO2 are removed by redistillation or blowing a current of carbondioxide or dry air through the warm acid
