Question

A black compound of manganese reacts with a halogen acid to give greenish yellow gas. When excess of this gas reacts with $NH_3$ an unstable trihalide is formed. In this process the oxidation state of nitrogen changes from

• A. $- 3$ to $+3$
• B. $- 3$ to $0$
• C. $- 3$ to $+5$
• D. $0$ to $-3$

Answer 1

Answer: (A)

$- 3$ to $+3$

Answer 2

$\underset{\text{(black)}}{ {MnO2}}\,+ {4HCl -> MnCl2 +}$ \underset{\text{(greenish yellow gas)}}{ {Cl2 ^}}+ {2H2O} $\overset{(-3)}{N}H_3\,+$ $\underset{\text{(excess)}}{ {3Cl2->}}$ $\overset{+3}{N}Cl_3 +3HCl$