MnO2 + 02 + KOH → K2Mn04 + H20

Balanced equation (in basic solution, with KOH spectator included to form K2MnO4):

2 MnO2 + O2 + 4 KOH → 2 K2MnO4 + 2 H2O

Check:

• Mn: 2 on both sides
• K: 4 on left, 4 on right
• O: left 4 (MnO2) + 2 (O2) + 4 (KOH) = 10; right 8 (2 K2MnO4) + 2 (H2O) = 10
• H: left 4 (KOH); right 4 (H2O)

Alternative (no K+): 2 MnO2 + O2 + 4 OH- → 2 MnO4^2- + 2 H2O.