Cân bằng phương trình sau: Fe(OH)2 + KMnO4 + H2SO4 → Fe2(SO4)3 + MnSO4 + K2SO4 + H2O

\[\mathop {Fe}\limits^{ + 2} {\left( {OH} \right)_2} + {\rm{ }}K\mathop {Mn}\limits^{ + 7} {O_4} + {\rm{ }}{H_2}S{O_4} \to {\rm{ }}{\mathop {Fe}\limits^{ + 3} _2}{\left( {S{O_4}} \right)_3} + {\rm{ }}\mathop {Mn}\limits^{ + 2} S{O_4} + {\rm{ }}{K_2}S{O_4} + {\rm{ }}{H_2}O\]

\[\left. {\begin{array}{*{20}{c}}{5 \times }\\{2 \times }\end{array}} \right|\begin{array}{*{20}{c}}{\mathop {2Fe}\limits^{ + 2} \to \mathop {2Fe}\limits^{ + 3} + 2e}\\{\mathop {Mn}\limits^{ + 7} + 5e \to \mathop {Mn}\limits^{ + 2} }\end{array}\]

10Fe(OH)₂ + 2KMnO₄ + 18H₂SO₄ → 5Fe₂(SO₄)₃ + 2MnSO₄ + K₂SO₄ + 28H₂O