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Q. Reaction of solid $KMnO_4$ with conc. $H_2SO_4$ produces manganese heptoxide $(Mn_2O_7)$ in

UP CPMTUP CPMT 2010The d-and f-Block Elements

Solution:

$KMnO_{4}$ on treatment with conc. $H_{2}SO_{4}$ forms manganese heptoxide via permanganyl sulphate which decomposes explosively on heating
$2KMnO_{4} + 3H_{2}SO_{4} \to 2KHSO_{4}+(MnO_{3})_{2} SO_{4} + 2H_{2}O$
$(MnO_{3})_{2} SO_{4} + H_{2}O \to \underset{\text{Red-brown liquid}}{{Mn_{2}O_{7}}}+ H_{2}SO_{4}$
$Mn_{2}O_{7} \to 2MnO_{2}+ \frac{3}{2}O_{2}$
$\therefore \, Mn_{2}O_{7}$ so formed is a red-brown liquid