$H_2O_2$ acts as oxidising and reducing agent in both acidic as well as in basic medium. $H_2O_2$ as an oxidizing agent (in acidic medium) $2FeSO_{4(aq)} + H_2SO_{4(aq)}$ + $H_2O_{2(aq)}$ → $Fe_2(SO_4)_{3(aq)} + 2H_2O_(l)$ $PbS_(s) + 4H_2O_{2(aq)}$ → $PbSO_{4(s)} + 4H_2O_(l)$ In basic medium : $MnSO_{4(aq)} + H_2O_{2(aq)}$ + $2NaOH_(aq)$ → $MnO_{2(s)} + Na_2SO_{4(aq)}$ + $2H_2O_(l)$ $H_2O_2$ as a reducing agent (in acidic medium) $2KMnO_{4(aq)}$ + $3H_2SO_{4(aq)} + 5H_2O_{2 (aq)}$ → $K_2SO_{4 (aq)} + 2MnSO_{4(aq)}$ + $8H_2O_(l) + 5O_{2 (g)}$ In basic medium : $2Fe^{3+}_(aq)$ + $H_2O_2(aq) + 2OH^{-}(aq)$ → $2Fe^{2+}_(aq)$ + $2H_2O_(l) + O_{2(g)}$