A violet compound of manganese 'A' decomposes on heating to liberate oxygen and compounds B and C of manganese are formed. Compound C reacts with KOH in the presence of potassium nitrate to give a compound B. On heating compound C with conc.
`H_(2)SO_(4)` and NaCl, chlorine gas is liberated and compound D of manganese alongwith other products is formed. Identify compounds A to D and also explain the reactions involved.

Explanation

Since, compound C on treating with conc. `H_(2)SO_(4)` and NaCl gives `Cl_(2)` gas, so it is manganese dioxide `(MnO_(2))`. It is obtained along with `MnO_(4)^(2-)` when `KMnO_(4)` (violet) is heated.
Thus,

`{:(A=KMnO_(4),B=K_(2)MnO_(4)):}`
`{:(C=MnO_(2),D=MnCl_(2)):}`
(i) `underset(A)(KMnO_(4))overset(Delta)(to)underset(B)(K_(2)MnO_(4))+underset(C)(MnO_(2))+O_(2)`
(ii) `2MnO_(2)+4KOH+O_(2) to 2K_(2)MnO_(4)+2H_(2)O`
(iii) `MnO_(2)+4NaCl+4H_(2)SO_(4) to underset(D)(MnCl_(2))+4NaHSO_(4)+2H_(2)O+Cl_(2)uarr`