When a brown compound of manganese [A] is treated with HCl, it gives a gas [B]. The gas taken in excess, reacts with `NH_(3)` to give as explosive compound [C]. Identify compound A, B and C.

Explanation

The available information suggests that the brown compound [A] is manganese dioxide `[MnO_(2)]`. The reaction involved are given as follows :
`underset((A))(MnO_(2)(s))+4Hcl(aq) to MnCl_(2)(aq)+2H_(2)O(aq)+underset((B))(Cl_(2)(g))`
`NH_(3)(g)+ underset("(Excess)")(3Cl_(2)(g)) to underset("Explosive(C)")(NCl_(3))+3HCl`