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:

C, B, A

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.