Question

When a brown coloured salt (A) of Mn reacts with HCl, a gas (B) is obtained. This gas in excess reacts with NH$_3$ to form an explosive salt (C). Identify (A), (B) and (C) and write the chemical equations.

Hint:

Chlorine with excess NH$_3$ can form explosive \(\mathrm{NCl_3}\); with excess NH$_3$ consumed and limited \(\mathrm{Cl_2}\), the main products are \( \mathrm{N_2} \) and \( \mathrm{NH_4Cl} \). Always note which reagent is in excess.

Answer 1

Identification: (A) = \(\mathrm{MnO_2}\) (brown–black solid); (B) = \(\mathrm{Cl_2}\); (C) = \(\mathrm{NCl_3}\) (explosive).
Equations:
Generation of chlorine from manganese dioxide and HCl:
\[ \mathrm{MnO_2 + 4HCl \;\longrightarrow\; MnCl_2 + Cl_2 + 2H_2O} \]
Action of \(\mathrm{Cl_2}\) (excess) on ammonia giving explosive nitrogen trichloride:
\[ \mathrm{3Cl_2 + NH_3 \;\longrightarrow\; NCl_3 + 3HCl} \]