Balance the following redox equation without using partial ionic equations: $PbS$ $+$ $H_2O_2$ $\longrightarrow$ $PbSO_4$ $+$ $H_2O$ - Look for the atoms whose oxidation number changes ! - How many electrons are exchanged by each of those atoms?
o.n.(S): -$2$ → $6$ : $8 e^-$ exchanges by each $S$ atom. o.n.(O): -1 → -2 : $1 e^-$ exchange by each $O$ atom.
How many electrons are exchanged by a "molecule" containing these atoms?
$8 e^-$ exchanged by each $PbSO_4$ $2 e^-$ exchanged by each $H_2O_2$.
What is the ratio of these molecules? Finish the balancing!
Ratio 1:4 $1$$PbS$ $+$$4$$H_2O_2$ $\longrightarrow$ $1PbSO_4$ $+$ $4H_2O$