Identify the gas evolved when:

(i) Sulphur is treated with conc. nitric acid.

(ii) A few crystals of KNO₃ are heated in a hard glass test tube.

Identify the acid which is :

(a) used for the preparation of non-volatile acid.

(b) prepared by cata­lytic oxidation of ammonia.

What is the property of nitric acid which allows it to react with copper?

Explain why

(a) Only all-glass apparatus should be used for the preparation of nitric acid by heating concentrated sulphuric acid and potassium nitrate.

(b) Nitric acid is kept in a reagent bottle for a long time.

(c) Iron is rendered passive with fuming HNO₃. Give reason.

(d) Dil. HNO₃ is generally considered a typical acid but not so in it's reaction with metals.

(e) When it is left standing in a glass bottle, concentrated nitric acid appears yellow.