(a) Name a drying agent for ammonia.

(b) How is hydrochloric acid prepared from HCl gas?

(c) Give the equations occurring at anode in the extraction of Aluminium.

(d) In the laboratory preparation, what must be added to sodium chloride to obtain HCI gas ?

(a) Quicklime (CaO)

(b) Hydrochloric acid is prepared by dissolving hydrogen chloride gas in water using a special funnel arrangement in which an inverted funnel, connected to the hydrogen chloride gas supply is placed in the beaker in such a way that it just touches the water taken in the trough. This arrangement minimizes back suction.

(c) Reaction at anode:

6O^2- - 12e- ⟶ 6[O]

3[O] + 3[O] ⟶ 3O₂

Anode is oxidised to carbon monoxide which further forms carbon dioxide

2C + O₂ ⟶ 2CO

2CO + O₂ ⟶ 2CO₂

(d) In the laboratory preparation of HCl, concentrated sulphuric acid (H₂SO₄) must be added to sodium chloride (NaCl) to obtain HCl gas.

1. $\text{NaCl} + \text{H}$2\text{SO}4 \xrightarrow{\lt 200 \degree\text{C}} \text{NaHSO}_4 + \text{HCl [g]} ↑

2. $\text{2NaCl} + \text{H}$2\text{SO}4 \xrightarrow{\gt 200 \degree\text{C}} \text{Na}2\text{SO}4 + \text{2HCl [g}] ↑