When nitric acid is prepared by the action of concentrated sulphuric acid on potassium nitrate, what is the special feature of the apparatus used.

Write the equation for the lab. preparation of HNO₃ from potassium nitrate and conc. H₂SO₄

State the conc. acid which will oxidise sulphur directly to H₂SO₄. Write the equation for the same.

X, Y and Z are three crystalline solids which are soluble in water and have a common anion. To help you to identify X, Y and Z, you are provided with the following experimental observation. Copy and complete the corresponding inference.

A reddish-brown gas is obtained when X, Y and Z are separately warmed with concentrated sulphuric acid and copper turnings added to the mixture. The common anion is the ………….. ion.