Question

A violet compound of manganese $\left(A\right)$ decomposes on heating to liberate oxygen and compounds $\left(B\right)$ and $\left(C\right)$ of manganese are formed. Compound $\left(C\right)$ reacts with $KOH$ in the presence of potassium nitrate to give compound $\left(B\right)$. On heating compound $\left(C\right)$ with conc. $H_{2}S{O}_4$ and $NaCl$, chlorine gas is liberated and a compound (D) of manganese along with other products is formed. Identify compounds A to D and also explain the reactions involved.

Answer 1

$Decompositionof{}^{\prime }{A}^{\prime }toproduce{}^{\prime }{B}^{\prime }\text{and}{}^{\prime }{C}^{\prime }$

The violet compound of manganese $\left(A\right)$ is potassium permanganate $\left(KMn{O}_4\right)$.

It decomposes on heating to liberate oxygen along with potassium manganate $\left(B\right)$ and manganese dioxide $\left(C\right)$.

$2KMn{O}_4\to K_{2}Mn{O}_4+MNn{O}_4+O_2$
$\left(A\right)$ $\left(B\right)$ $\left(C\right)$


Reaction of ${}^{\prime }{C}^{\prime }$ with $KOH$ to produce ${}^{\prime }{B}^{\prime }$

$Mn{O}_2$ with an alkali metal hydroxide forms dark green $K_{2}Mn{O}_4$:

$Mn{O}_4+KOH+O_2\to 2K_{2}Mn{O}_4+2H_{2}O$
$\left(C\right)$ $\left(B\right)$


Reaction of ${}^{\prime }{C}^{\prime }$ with concentrated $H_{2}S{O}_4$ to produce ${}^{\prime }{D}^{\prime }$

On heating manganese dioxide $\left(C\right)$ with conc. $H_{2}S{O}_4\text{and}NaCl$, formation of manganese chloride $\left(D\right)$ along with chlorine gas takes place.



Hence, $A:KMn{O}_4,B:Mn{O}_4,C:Mn{O}_4,D:MnC{l}_2$