Question

Balance this half-reaction: MnO4- → MnO2 (basic solution)

Answer 1

It would be MbO4-   ------> MnO2+ 2H2O

Answer 2

Balance atoms: (for everything except oxygen and hydrogen):

MnO4- → MnO2 (atoms are balanced)

Balance oxygen:

MnO4- → MnO2 + 2H2O

Balance hydrogen:

4H+ + MnO4- → MnO2 + 2H2O

Make adjustments for basic solution.

Add hydroxide ions to balance hydrogen:

4OH- + 4H+ + MnO4- → MnO2 + 2H2O + 4OH-

Remove hydrogen by forming water molecules and removing them:

4H2O + MnO4- → MnO2 + 2H2O + 4OH-

Cancel out any water molecules that are on both sides of the equation:

2H2O + MnO4- → MnO2 + 4OH-

Balance charge:

2H2O + MnO4- +3e- → MnO2 + 4OH-