Question

What is observed when nitric acid is kept in a reagent bottle for a long time?

• A. Brown vapours are seen in the bottle
• B. The nitric acid turns yellowish in colour
• C. The nitric acid turns black in colour
• D. both A and B

Answer 1

Answer: (D)

both A and B

:

1. Nitric acid takes yellowish brown colour due to the presence of dissolved nitrogen dioxide.
2. Nitric acid slowly decomposes even at room temperature, specially in the presence of sunlight. $4HN{O}_3\to 4N{O}_2+2H_{2}O+O_2$ Liberated nitrogen dioxide dissolves in the acid and gives a yellow colour.
3. Brown vapours are seen in the bottle and the nitric acid turns yellowish in colour.