One mole black lead sulphide $\left(\mathrm{PbS}\right)$ is oxidised to white lead sulphate $\left({\mathrm{PbSO}}_4\right)$ by mole of ozone

Being a strong oxidising agent, ozone can oxidise $\mathrm{PbS}$ to ${\mathrm{PbSO}}_4$ along with liberation of oxygen gas.

$4{\mathrm{O}}_3+\mathrm{PbS}\to {\mathrm{PbSO}}_4+4{\mathrm{O}}_2$