Question

Explain the following :
i) $Dil.HN{O}_3$ is generally considered a typical acid but not so in the reaction with metals.
ii) Concentrated nitric acid appears yellow when it is left standing in a glass bottle.
iii) In the laboratory preparation of nitric acid an all-glass apparatus is used.

Answer 1

i) Dilute nitric acid is generally considered a typical acid but not in its reaction with metals because the action of nitric acid on metals depends on the temperature and concentration of nitric acid. These conditions are not required in the case of hydrochloric acid and sulphuric acid.
ii) Although pure concentrated nitric acid is colourless, it appears yellow when left standing in a glass bottle due to the dissolution of reddish-brown nitrogen dioxide gas in the acid.
iii) The apparatus used for the laboratory preparation of nitric acid are made of glass completely because the vapours of nitric acid are highly corrosive. They attack rubber cork, plastics etc.