A `0.1g` sample of pyrolusite ore containing `MnO_(2)(MW = 87)` was dissolved in a concentrated `HCI` solutiona and liberated `CI_(2)(g)` was passed through a concentrated `KI` solution releasing `I_(2)` if the liberated iodine required 16 ml of `1.25M` sodium thiosulphate `(Na_(2)S_(2)O_(3))` solution, mass percentage of `MnO_(2)` in the given sample is

Options

A. `43.5%`
B. `87%`
C. `21.75%`
D. `0.875%`

Answer

B

Explanation

No. of m.eqts `MnO_(2) =` No. of m.eqts of `Cl_(2)`
= No. of m.eqts of `KI =` No. of m.eqts hypo No. of m.eqts
`= MnO_(2) = 16 xx 1.25 = 16 xx (5)/(4) =20`
No. of milli moles of `MnO_(2) = 10`
weight of `MnO_(2) = 10 xx 87 xx 10^(-3) = 0.87g`
weight % of `MnO_(2) = (0.87)/(1) xx 100 = 87%`