(a) A bottle of liquor ammonia should be cooled before opening. Give reason.
(b) Why conc. `H_2 SO_4`, anhydrous `CaCl_2` and `P_4 O_10` cannot be used as dehydrating agents for ammonia.

Explanation

(a) Liquor ammonia hsd high vapour pressure at room temperature. Hence, to reduce the vapour pressure inside the bottle in order to avoid bumping, it has to be cooled.
(b) Conc. `H_2 SO_4`, anhydrous `CaCl_2`and `P_4 O_10` react with ammonia and hence do not behave as dehydrating agent.
`H_2 SO_4 + 2 NH_3 rarr (NH_4)_2 SO_4`
`CaCl_2 + 8 NH_3 rarr CaCl_2. 8 NH_3`
`P_4 O_10 +12 NH_3 + 6 H_2 O rarr 4(NH_3)_3 PO_4`.