Given below is the diagram for the laboratory preparation of Nitric Acid.

(a) Name the reactant labelled Y.

(b) Write a balanced equation for the reaction between Y and KNO₃.

(c) The complete apparatus is made up of glass. Why?

(d) State why concentrated HNO₃ appears slightly yellowish in colour when left standing in a glass bottle for a long time.

(a) Conc. sulphuric acid

(b)

$\underset{[conc.]}{\text{KNO}$3} + \underset{[conc.]}{\text{H}2\text{SO}4} \xrightarrow{\lt 200 \degree\text{C}} \underset{[acid \space salt]}{\text{KHSO}4} + \text{HNO}_3

(c) The complete apparatus is made up of glass because nitric acid vapours attack rubber and cork.

(d) Pure acid is colourless but the acid obtained in the laboratory is slightly yellow. The yellow colour is due to dissolution of reddish brown coloured nitrogen dioxide gas in the acid. This gas is produced due to the thermal decomposition of a portion of nitric acid.
4HNO₃ ⟶ 2H₂O + 4NO₂ + O₂