J.R. S. answered • 12/09/22
Ph.D. University Professor with 10+ years Tutoring Experience
Mn2+(aq) + O2(g) ==> MnO2(s) .. unbalanced redox equation
Mn2+ ==> MnO2 .. unbalanced oxidation reaction (Mn goes from 2+ to 4+)
Mn2+(aq) + 2H2O ==> MnO2(s) .. balanced for Mn and O
Mn2+(aq) + 2H2O + 4OH- ==> MnO2(s) + 4H2O .. balance for Mn, O and H (using base, OH-)
Mn2+(aq) + 4OH- ==> MnO2(s) + 2H2O + 2e- .. balanced for Mn,O,H and charge = BALANCED EQ
O2 ==> 2O2- .. unbalanced reduction reaction (O goes from zero to 2-)
O2 + 2H2O + 4e- ==> 4OH- .. BALANCED EQ
Multiply the oxidation reaction by 2 in order to equalize electrons, then add the two together. Combine/cancel like terms to end up with the final balanced redox equation:
2Mn2+(aq) + 8OH- ==> 2MnO2(s) + 4H2O + 4e-
O2 + 2H2O + 4e- ==> 4OH-
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2Mn2+(aq) + 4OH- + O2 ==> 2MnO2(s) + 2H2O .. BALANCED REDOX EQUATION
