Question

Manganese dioxide on heating with conntrated hydrochloric acid gives a greenish yellow gas, X. With exss of ammonia X gives Y and Z. Y and Z respectively are

• A. ${NH_4F}, {N_2}$
• B. ${NH_4I}, {NOCl}$
• C. ${NCl_3}, {HOCl}$
• D. ${NH_4Cl}, {N_2}$

Hint:

Reactivity of Chlorine with Ammonia:

• Limited Cl$_2$ leads to formation of N$_2$ and NH$_4$Cl.
• Excess Cl$_2$ would produce NCl$_3$ instead (explosive).
• This reaction is redox in nature: ammonia is oxidized, chlorine is reduced.

Answer 1

The Correct Option is D

The reaction between manganese dioxide and hydrochloric acid is:

\[ \mathrm{MnO_2} + 4 \mathrm{HCl} \rightarrow \mathrm{MnCl_2} + \mathrm{Cl_2} + 2 \mathrm{H_2O} \]

So, the greenish yellow gas X is chlorine (\( \mathrm{Cl_2} \)).

When excess ammonia is passed through chlorine gas, a redox reaction occurs. Chlorine reacts with ammonia as follows:

\[ \mathrm{Cl_2} + 2 \mathrm{NH_3} \rightarrow \mathrm{NH_4Cl} + \mathrm{N_2} \]

In this reaction, chlorine oxidizes ammonia, producing nitrogen gas (\( \mathrm{N_2} \)) and ammonium chloride (\( \mathrm{NH_4Cl} \)).

Hence, the correct identities are:

\[ X = \mathrm{Cl_2}, \quad Y = \mathrm{NH_4Cl}, \quad Z = \mathrm{N_2} \]

Answer 2

Step 1: Reaction of manganese dioxide with concentrated hydrochloric acid
When manganese dioxide (MnO₂) is heated with concentrated hydrochloric acid (HCl), it produces manganese(II) chloride (MnCl₂), water, and a greenish-yellow gas X, which is chlorine gas (Cl₂).

Step 2: Reaction of chlorine gas with excess ammonia
Chlorine gas (X) reacts with excess ammonia (NH₃) to give a mixture of ammonium chloride (NH₄Cl) and nitrogen gas (N₂).

Step 3: Identify products Y and Z
In the reaction of Cl₂ with excess NH₃, the products are:
Y = NH₄Cl (ammonium chloride) and
Z = N₂ (nitrogen gas).

Step 4: Conclusion
Therefore, the greenish-yellow gas X is chlorine (Cl₂), and with excess ammonia it produces Y = NH₄Cl and Z = N₂.