Chemistry [2 Mark Question Answer]

An all-glass apparatus is used in the laboratory preparation of nitric acid because nitric acid vapour corrodes rubber and cork.

Dilute nitric acid is generally considered a typical acid except for its reaction with metals because it does not liberate hydrogen. It is a powerful oxidising agent, and nascent oxygen formed oxidises hydrogen in water.

At high temperature, nitric acid decomposes and the glass apparatus may get damaged. Sodium formed at a higher temperature forms a hard crust which sticks to the walls of the retort.

In a glass apparatus nitric acid gets decomposed by sunlight. Yellowish brown colour of nitric acid is due to the presence of nitrogen dioxide formed due to thermal decomposition of nitric acid.

Dilute nitric acid is generally considered a typical acid except for its reaction with metals because it does not liberate hydrogen. It is a powerful oxidising agent, and nascent oxygen formed oxidises hydrogen in water.

Yellowish brown colour of nitric acid is due to the presence of nitrogen dioxide formed due to thermal decomposition of nitric acid.

For laboratory preparation of nitric acid potassium nitrate or sodium nitrate and conc. sulphuric acid is required.

Gold will dissolve only in aqua regia i.e., a mixture of conc. hydrochloric acid and conc. nitric acid in 1:3 but copper will dissolve in nitric acid.
To separate gold from a mixture of gold and platinum add some nitric acid to the mixture, gold will remain undissolved hence can be filtered.

Nitric acid usually do not yield hydrogen gas with metals, instead it reacts with metals and form respective nitrates , nitric oxide and water.

Concentrated nitric acid renders iron passive because of the formation of extremely thin, unreactive, protective layer of insoluble metallic oxide on the surface which stops further reaction.

Aluminum does not react with nitric acid of any concentration because of the formation of extremely thin, unreactive, protective layer of insoluble metallic oxide on the surface of aluminium which stops further reaction.

Commercial nitric acid is yellow in colour because of presence of nitrogen dioxide but when it is diluted with water, it turns colourless because nitrogen dioxide get dissolved in water.

ln laboratory preparation of nitric acid all the apparatus including cork should be made up of glass because nitric acid vapours are highly corrosive in nature and corrodes cork, rubber etc.

lf the test tube is disturbed brown ring will disappear because the complex formed will get dissolved in the layers of the liquid.

Freshly prepared ferrous sulphate solution is used in the ring test otherwise. Ferrous sulphate undergoes aerial oxidation and converts to ferric sulphate.

Aqua Regia: It is a mixture of concentrated nitric acid and concentrated hydrochloric acid in proportionof 1:3 (by volume).

Aqua fortis : It is the other name for nitric acid, it is also known as strong water. It was called so because earlier this was the only liquid which could dissolve many metals including silver.