question_answer

On heating, \[{{(N{{H}_{4}})}_{2}}C{{r}_{2}}{{O}_{7}}\] 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 cone. HCl is brought in its contact. Identify the gas X.

Answer:

                The available information suggests that the gas (X) is ammonia. The chemical reactions involved are as follows: \[{{(N{{H}_{4}})}_{2}}C{{r}_{2}}{{O}_{7}}\xrightarrow{heat}\,\,C{{r}_{2}}{{O}_{3}}+{{N}_{2}}+4{{H}_{2}}O\] \[3Mg\,+{{N}_{2}}\,\xrightarrow{\,\,}\,\,M{{g}_{3}}{{N}_{2}}\] \[M{{g}_{3}}{{N}_{2}}+6{{H}_{2}}O\xrightarrow{\,}\,3Mg\,{{(OH)}_{2}}+\underset{\begin{smallmatrix}  \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\text{(X)} \\  \text{White}\,\text{fumes}\,\text{with}\,\text{HCl} \end{smallmatrix}}{\mathop{2N{{H}_{3}}}}\,\]