1) 2KMnO4 + Zn + 4KOH = 2K2MnO4 + K2[Zn(OH4)], баланс:
(MnO4)- +e- = (MnO4)2- | 1 | 2 | 2 |
Zn -2e- + 4OH- = [Zn(OH)4]2- | 2 | | 1 |;
2(MnO4)- + Zn + 4OH- = 2(MnO4)2- + [Zn(OH)4]2-;
3) K2Cr2O7 + 3NaNO2 + 4H2SO4 = K2SO4 + Cr2(SO4)3 + 3NaNO3 + 4H2O, баланс:
(Cr2O7)2- +6e- + 14H+ = 2Cr3+ + 7H2O | 6 | 6 | 1 |
(NO2)- -2e- + H2O = (NO3)- + 2H+ | 2 | | 3 |;
(Cr2O7)2- + 3(NO2)- + 8(H3O)+ = 2Cr3+ + 3(NO3)- + 12H2O.