Question

`KMnO_(4)` acts as an oxidising agent in acidic medium. The number of moles of `KMnO_(4)` that will be needed to react with one mole of sulphide ions in acidic solution is
A. `(2)/(5)`
B. `(3)/(5)`
C. `(4)/(5)`
D. `(1)/(5)`

Answer 1

The reaction of `KMnO_(4)` in which it acts as an oxidising agent in acidic medium is
`2KMnO_(4)+3H_(2)SO_(4) rarrK_(2)SO_(4)+2MnSO_(4)+3H_(2)O+5[O]`
`(H_(2)S+[O]rarrH_(2)O+Sxx5)/(2KMnO_(4)+3H_(2)SO_(4)+5H_(2)SrarrK_(2)SO_(4)+2MnSO_(4)+8H_(2)O+5S)`
5 moles of `S^(2-)` ions react with 2 moles of `KMnO_(4)`. So, 1 mole of `S^(2-)` ion will react with `(2)/(5)` moles of `KMnO_(4)`.