Question

Balance the following equation by oxidation number method
`PbS+H_(2)O_(2) to PbSO_(4)+H_(2)O`

Answer 1

Writing oxidation number of all the atoms,
`overset(+2 ,-2)(PbS)+overset(+1, -1)(H_(2)O_(2)) to overset(+2 +6 -2)(PbSO_(4))+overset(+1, -2)(H_(2)O)`
The oxidation number S has increased and O has decreased.
`Pboverset(-2)(S) to Pboverset(+6)(SO_(4)) ...(i)`
`H_(2)overset(-1)(O_(2))to H_(2)overset(-2)(O) ....(ii)`
Increase in Ox. no. of S=8 unit per PbS moleucle
Decrease of Ox. no. of O=1 unit per `(1)/(2) H_(2)O_(2)` molecule =2 unit per `H_(2)O_(2)` molecules
Multiplying eq. (ii) by 4 as to make increase and decrease equal
`PbS+4H_(2)O_(2) to PbSO_(4)+4H_(2)O`
This is the balanced equation.