0.6 g of a sample of pyrolusite was boiled with 200 " mL of " `(N)/(10)` oxalic acid and excess of dilute sulphuric acid. The liquid was filtered and the residue washed. The filtrate and washing were mixed and made up to 500 mL in a measuring flask. 100 " mL of " this solution required 50 " mL of " `(N)/(30)KMnO_4` solution. Calculate the percentage of `MnO_2` in the sample `(Mn=55)`.

Options

A. `10.86%`
B. `5.43%`
C. `1.086%`
D. none of these

Answer

B

Explanation

`m" Eq of "KMnO_(4)-=m" Eq of "H_(2)C_(2)O_(4)]_("excess in "25 mL)`
`impliesexcess m" Eq of "H_(2)C_(2)O_(4)` in 25 mL
`=0.01xx30=0.30`
Excess m" Eq of "`H_(2)C_(2)O_(4)` in 250 mL`=3.0mL`
m" Eq of "`H_(2)C_(2)O_(4)` used `=5-3=2`
`m" Eq of "MnO_(2)=2`
`(Weight)/((87)/(2))xx1000=2impliesweight=0.087g`
`% MnO_(2)=(0.087)/(1.6)xx100=5.43%`