On heating, `(NH_(3))_(2)Cr_(2)O_(7)` gives rise to a gas which on treatment with `Mg` ribbon gives a white solid. On dissolving white solid in water another gas `(X)` is evolved. It gives white fumes when a rod dipped in conc. `HCl` is brought in its contact. Identify the gas `X`.

Explanation

The available information suggests that the gas (X) is ammonia. The chemical reactions involved are as follows :
`(NH_(4))_(2)Cr_(2)O_(7) overset("heat")to Cr_(2)O_(3)+N_(2)4H_(2)O`
`3Mg+N_(2)to Mg_(3)N_(2)`
` Mg_(3)N_(2)+6H_(2)O to 3Mg(OH)_(2)+underset("White fumes with HCl")underset((X))(2NH_(3))`