pbs+ 4h2o2 = pbso4 + 4h2o2, which substance is reduced and which is oxidised?
Checking what the oxidation states of the elements are. H is +1 when not bound to a metal, O and S are -2 when bound to elements of lower electronegativity only.
With 2+1 ON in H2O2, the O2 entity has to be -2, meaning O is -1. S is -2 in PbS, so Pb is +2. Sulfate has a charge of -2, so Pb is still +2. O is -2 here, so work out S. S = -[+2 - 4(-2)] = -(-6) = +6. H in H2O is still +1, so O is -2.