1)K2Cr2O7 + 3 H2SO3 + H2SO4 → Cr2(SO4)3 + K2SO4 + 4 H2O Cr(6) + 3 e- → Cr(3) SI(5) - 2 e- → S(6)
2)HIO3+5HI-->3H2O+3I2 2I(+5) +10e-->I2(0) [1]
2I(-1) -2e-->I2(0) [5]
3)2MnSO4+5PbO2 +6HNO3 = 2HMnO4+ 3Pb(NO3)2 +2PbSO4+2H2O
5Pb(+4) +10e = 5Pb(+2)
2Mn(+2) - 10e = 2Mn(+7)
4)2KCIO3=2KCI+3O2
СI+6e→СI
2О-4e→2О