KCET · Chemistry · d and f Block Elements

When a brown compound of \( M n(A) \) is treated with \( H C l \), it gives a gas (B). The gas (B) taken in
excess reacts with \( \mathrm{NH}_{3} \) to give an explosive compound (C).
The compounds A, B and C are;

A \( \mathrm{A}=\mathrm{MnO}_{2}, \mathrm{~B}=\mathrm{Cl}_{2}, \mathrm{C}=\mathrm{NCl}_{3} \)
B \( A=M n O, B=C l_{2}, C=N H_{4} C l \)
C \( \mathrm{A}=\mathrm{Mn}_{3} \mathrm{O}_{4}, \mathrm{~B}=\mathrm{Cl}_{2}, \mathrm{C}=\mathrm{NCl}_{3} \)
D \( \mathrm{A}=\mathrm{MnO}_{3}, \mathrm{~B}=\mathrm{Cl}_{2}, \mathrm{C}=\mathrm{NCl}_{2} \)

Verified Solution

Answer & Solution

Correct Answer

(A) \( \mathrm{A}=\mathrm{MnO}_{2}, \mathrm{~B}=\mathrm{Cl}_{2}, \mathrm{C}=\mathrm{NCl}_{3} \)

Step-by-step Solution

Detailed explanation

When a brown compound of \( M n(A) \) is treated with \( H C l \), it gives a gas (B) as shown below.
\( \mathrm{MnO}_{2}(\mathrm{~A})+4 \mathrm{HCl} \rightarrow \mathrm{MnCl}_{2}+2 \mathrm{H}_{2} \mathrm{O}+\mathrm{Cl}_{2}(\mathrm{~B}) \)
The gas (B) taken in excess reacts with \( \mathrm{NH}_{3} \) to give an explosive compound (C) as shown below.
\( 3 \mathrm{Cl}_{2}(B)+\mathrm{NH}_{3} \rightarrow \mathrm{NCl}_{3}(C)+3 \mathrm{HCl} \)
Therefore, the compounds \( A, B \) and \( C \) are
\( \mathrm{MnO}_{2}, \mathrm{Cl}_{2} \), and \( \mathrm{NCl}_{3} \).

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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When a brown compound of \( M n(A) \) is treated with \( H C l \), it gives a gas (B). The gas (B) taken inexcess reacts with \( \mathrm{NH}_{3} \) to give an explosive compound (C).The compounds A, B and C are;

Step-by-step Solution

When a brown compound of \( M n(A) \) is treated with \( H C l \), it gives a gas (B). The gas (B) taken in
excess reacts with \( \mathrm{NH}_{3} \) to give an explosive compound (C).
The compounds A, B and C are;