20 mL of `Fe^(2+)` solution of certain concentration has completely reacted with 20 mL of 0.01 M `K_(2) Cr_(2) O_(7)` in acidic medium .If 20 mL of same `Fe^(2+)` solution has reacted completely with 20 mL of `KMnO_(4)` solution in acid medium the molarity of `KMnO_(4)` solution is

Options

A. `0.01 M`
B. `0.12 M`
C. `0.10 M`
D. `0.012 M`

Answer

D

Explanation

The reaction between `Fe^(2+)` and `Cr_(2)O_(7)^(2-)`
`Cr_(7)O_(7)^(2-) + 14H^(+) + 6Fe^(2+) to 2Cr^(3+) + 7H_(2) O + 6Fe^(2+)`
The reaction between `Fe^(2+) ` and `MnO_(4)^(-)`
`MnO_(4)^(-) + 8H^(+) + 5Fe^(2+ ) to Mn^(2+) + 4H_(2) O + 5Fe^(3+)`
`Cr_(2) O_(7)^(2-) ` react with 6 `Fe^(2+) n_(1)` and `MnO_(4)^(-)` react with Gram equlvalent of `Fe^(2+)`
Conc. of `K_(2) Cr_(2) O_(7)= 0.01 (m(m_(1))`
Volume of `k_(2) Cr_(2)O_(7) = ` 20 mL (`V_(1)`)
Conc. of `MnO_(4) =` to find (say `M_(2)`)
Volume of `KMnO_(2) =20 mL (V_(2))`
Thus `M_(1) xx V_(1) xx n_(1) = m_(2) xx v_(2) xx n_(2)`
or 0.01 `xx 20xx 6 = m_(2) xx 20 = 5`
`M_(2) = ( 0.01 xx 6)/(5) = 0.012 M`
Hence option ( d) is the correct answer