An impure sample of pyrolusite ore `(MnO_2)` consist of 70 % `MnO_2`, 20% inert impurities and rest is the moisture. On strong heating, all `MnO_2` is converted into MnO alongwith formation of `O_2` . What is the% of Mn in dried sample? (Atomic mass of Mn = 55)

Options

A. 57 .4 %
B. 0.5
C. 0.478
D. 0.701

Answer

A

Explanation

`underset((70/87))(MnO_2) rarr underset((70/87))(MnO) + 1/2O_2`
% mass of Mn = `(((70)/(87))55xx100)/(((70)/(87))71+20)`=`(44.25)/(57+20)xx100 = 57`
4 %