An orange solid `(A)` on heating gave a green residue `(B)`, colourless gas `( C)` and water vapour. The dry gas `( C)` on passing over heated magnesium gave a white solid `(D).(D)` on reaction with water have a gas `( E)` which formed dense white fumes with `HCl`. Indentify `(A)` to `( E)` and give the reactions.

Explanation

The gas E must be ammonia so D is maganessium nitride and gas C is mirogen, It is expected that the orange solid A is ammonium dishromade .The green residue B is `Cr_(2)O_(3) `
`underset((A))((NH_(4))_(2)Cr_(2)O_(7))rarrunderset((B))(Cr_(2)O_(3))+underset((C))(N_(2))+4H_(2)O`
`N_(2) +3Mg rarr underset((D))(Mg_(3)N_(2))`
`Mg_(3)N_(2)+6H_(2)O rarr 3Mg(OH)_(2) +underset((E))(2NH_(3))`
`NH_(3) +HCI rarr NH_(4)CI` (Dense white fumes)