Pyrolusite on heating with KOH in the presence of air gives a dark gre

1.	Pyrolusite on heating with KOH in the presence of air gives a dark green compound (A). The solution of (A) on treatment with H2SO4 gives a purple coloured compound (B).(a). Identify ‘A’ and ‘B’ and write the balanced chemical equation.(b). Write two reactions to show the oxidising nature of ‘B’.
Answer» (a). A - K₂MnO₄ B - KMnO₄ 2MnO₄ + 4KOH + O₂ \(\longrightarrow\) 4K₂MnO + 2H₂O K₂MnO₄ \(\overset{H_2SO_4}\longrightarrow\) KMnO₄ (b). 10I^- +2MnO₄^- + 16H⁺ \(\longrightarrow\) 2Mn²⁺ + 8H₂O +5I₂ 5Fe²⁺ + MnO₄- + 8H⁺ \(\longrightarrow\) Mn²⁺ + 4H₂O + 5Fe³⁺

Pyrolusite on heating with KOH in the presence of air gives a dark green compound (A). The solution of (A) on treatment with H2SO4 gives a purple coloured compound (B).(a). Identify ‘A’ and ‘B’ and write the balanced chemical equation.(b). Write two reactions to show the oxidising nature of ‘B’.

Answer»

(a). A - K₂MnO₄

B - KMnO₄

2MnO₄ + 4KOH + O₂ \(\longrightarrow\) 4K₂MnO + 2H₂O

K₂MnO₄ \(\overset{H_2SO_4}\longrightarrow\) KMnO₄

(b). 10I^- +2MnO₄^- + 16H⁺ \(\longrightarrow\) 2Mn²⁺ + 8H₂O +5I₂

5Fe²⁺ + MnO₄- + 8H⁺ \(\longrightarrow\) Mn²⁺ + 4H₂O + 5Fe³⁺