What is the normality of a $K M n O_{4}$ solution in which $15.8 g$ of $K M n O_{4}$ is present in $250 m L$ solution and the solution is used as an oxidant, where ${M n O_{4}}^{-}$ is reduced to ${M n}^{2 +}$ ? (Given: molar mass of $K M n O_{4} = 158 g m o l^{- 1}$ )

0.4 N

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20 N

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2 N

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40 N

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Solution

The correct option is C
2 N

We know that,

Normality = $\frac{N u m b e r o f g r a m e q u i v a l e n t s o f s o l u t e}{V o l u m e o f s o l u t i o n (i n l i t r e s)}$

Equivalent Mass = $\frac{M o l e c u l a r m a s s}{V a l e n y f a c t o r}$

${M n O_{4}}^{-}$ $\to$ ${M n}^{2 +}$

[ ${M n}^{7 +}$ + 5 $e^{-}$ $\to$ ${M n}^{2 +}$ ]

$\to$ Valency factor = 5

Molecular mass of $K M n O_{4}$ = 158

$∴$ equivalent weight = $\frac{158}{5}$ = 31.6

No of gram equivalents = $\frac{15.8}{31.6}$

$∴$ Normality $= \frac{\frac{15.8}{31.6}}{250 \times 10^{- 3}} = 2 N$

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What is the normality of a $K M n O_{4}$ solution in which $15.8 g$ of $K M n O_{4}$ is present in $250 m L$ solution and the solution is used as an oxidant, where ${M n O_{4}}^{-}$ is reduced to ${M n}^{2 +}$ ? (Given: molar mass of $K M n O_{4} = 158 g m o l^{- 1}$ )