ON adding NaOH to ammonium sulphate, a colourless gas with pungent odour is evolved which forms a blue coloured complex with `Cu^(2+)` ions. Identify the gas.

Explanation

Ammonium sulphate reacts with NaOH to evolve `NH_(3)` gas which has pungent smell and forms blue coloured complex with `Cu^(2+)` ions as shown below :
`underset("Amm. Sulphate")((NH_(4))_(2)SO_(4))+2NaOHtounderset("Ammonia")(2NH_(3))uarr+Na_(2)SO_(4)+2H_(2)O`
`underset("Copper (II) ion")(Cu^(2+)(aq.))+4NH_(3)(aq.)toundersetunderset(("Bule coloured complex"))("Tetraamminecopper (II) ion")([Cu(NH_(3))_(4)]^(2+)(aq.))`