Redox Reaction

There are a set of half-reactions which students need to know;

H₂O₂ + 2H⁺ + 2e^- ----> 2H₂O

MnO₄^- + 8H⁺ + 5e^- ----> Mn²⁺ + 4H₂O

Cr₂O₇^2- + 14H⁺ + 6e^- ----> 2Cr³⁺ + 7H₂O

MnO₂ + 4H⁺ + 2e^- ----> Mn²⁺ + 4H₂O

O₂ + 4H⁺ + 4e^- ----> 2H₂O

NO₃^- + 4H⁺ + 3e^- ----> NO + 2H₂O

SO₄^2- + 4H⁺ + 2e^- ----> SO₂ + 2H₂O

2H₂O + 2e^- ----> H₂ + OH^-

Do not forget the table of standard reduction potentials included in the exam. It does not happen everytime, but that table often yields half reactions for part if not for a complete equation in Problem 4.