Ostwald's process for the manufacture of nitric acid involves three steps. Arrange them in correct sequence:
A. 3NO2(g) + H2O(l) → 2HNO3(aq) + NO(g)
B. 2NO(g) + O2(g) → 2NO2(g)
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
In the laboratory, nitric acid is prepared by heating KNO3 or NaNO3 and concentrated H2SO4 in a glass retort.
NaNO3 + H2SO4 → NaHSO4 + HNO3
On a large scale it is prepared mainly by Ostwald’s process. This method is based upon catalytic oxidation of NH3 by atmospheric oxygen.
Nitric oxide thus formed combines with oxygen giving NO2.
B. 2NO(g) + O2(g) → 2NO2(g)
Nitrogen dioxide so formed, dissolves in water to give HNO3.
A. 3NO2(g) + H2O(l) → 2HNO3(aq) + NO(g)
NO thus formed is recycled and the aqueous HNO3 can be concentrated by distillation up to ~ 68% by mass. Further concentration to 98% can be achieved by dehydration with concentrated H2SO4.