The equivalent weight of potassium permanganate in acid solution is

Options

A. 158
B. `31.6`
C. 79
D. `39.5`

Answer

B

Explanation

`KMnO_4` oxidises ferrous sulphate to ferric sulphate as per the equation
`2KMnO_4 + 8H_2SO_4 + 10FeSO_4 rarr K_2SO_4+2MnSO_4 +5Fe_2(SO_4)_3 + 8H_2O`
`2MnO_(4)^(-) , +16H^(+) +10Fe^(2+) rarr 2Mn^(2+) + 8H_2O+10Fe^(3+)`
and equivalent mass of an oxidising/reducing agent
`= ("Mol. mass or atomic mass")/("No. of electrons lost or gained by one molecule of the substance")`
`:.` Mol. mass of `KMnO_4 = 39 + 55 + 64 = 158`
and electrons lost `=[ MnO_(4)^(-) (+7)" to " Mn^(2+) (+2)]`
Eq.wt. = 158/5 = 31.6