Question

(a) How is nitric acid prepared in laboratory?
(b) What is the purpose of conc. H₂SO₄ in the above preparation?
(c) Why is the temperature maintained at 200°C in the above reaction?
(d) Can we use conc. HCl in place of conc. H₂SO₄?

Answer 1

1. Nitric acid is prepared in the laboratory by the reaction of sulphuric acid with sodium nitrate or sodium nitrate.
2. The concentrated sulphuric acid in the preparation reduces the nitrates into nitric acid. Further, sulphuric acid is not volatile. As a result, nitric acid vapours can be collected without contamination from sulphuric acid.
3. The temperature is maintained at 200^oC for the following reasons:
   1. To avoid the decomposition of nitric acid into nitrogen dioxide
   2. To prevent the formation of sodium sulphate or potassium sulphate that may stick to the glass and cannot be removed easily.
   3. To prevent the cracking of glass apparatus