One litre of an acidified solution of `KMnO_4` containing 15 g of `KMnO_4` is decolourised by passing sufficient amount of `SO_2`. If `SO_2`. If `SO_2` is produced by roasting of iron pyrites `(FeS_2)`. What will be the amount of pyrites required to produce the necessary amount of `SO_2`

Explanation

v.f. of `KMnO_(4)=5 ` & v.f. of `SO_(2)=2`
Now, Eq. of `KMnO_(4)`=Eq. of `SO_(2)`
`(15.8)/(158//5)`=moles of `SO_(2)xx2`
so, moles of `SO_(2)=1//4`
Now, applying POAC on S, we get :
`2xx` mole of `FeS_(2)=1xx` moles of `SO_(2)`
so, moles of `FeS_(2)=(1)/(4)xx(1)/(2)=(1)/(8)`
so, weight of `FeS_(2)=(1)/(8)xx120=15g`.