A metal `M` reacts with `N_(2)` to give a compound `'A'(M_(3)N)`. 'A' on heating at high temperature gives back `'M'` and `'A'` on reacting with `H_(2)O` gives a gas 'B'.'B' turns `CuSO_(4)` solution blue on passing through it `A` and `B` can be

Options

A. `Al` and `NH_(3)`
B. `Li` and `NH_(3)`
C. `Na` and `NH_(3)`
D. `Mg` and `NH_(3)`

Answer

B

Explanation

Lithium forms nitride on heating with nitrogen. Lithium nitride gives ammonia when heated with `H_(2)O`. Ammonia gas forms tetrammine copper complex with `CuSO_(4)` solution.
`6Li+N_(2) rarr 2Li_(3)N`
`Li_(3)N+3H_(2)O rarr 3LiOH+NH_(3)`
`CuSO_(4)+4NH_(3) rarr [Cu(NH_(3))_(4)]SO_(4)`