Lesson 3: Balancing Redox Reactions

• Balancing Redox Reactions in acidic or basic solutions

  1. In Acidic Solutions (half reaction method):

  2. Write the half reactions (do not include electrons)

  3. Balance all atoms except Oxygen and Hydrogen

  4. Balance Oxygen atoms by adding H2O to the side that needs O.

  5. Balance hydrogen by adding H+ to the side that needs H

  6. Balance the charge by adding electrons to the side with more positive charge

  7. Make electrons gained equal to electrons lost

  8. Add the two half-reactions to get the overall equation.
• Balancing Redox Reactions in acidic or basic solutions

  1. In Basic Solutions (half reaction method):

  2. Write the half reactions (do not include electrons)

  3. Balance all atoms except Oxygen and Hydrogen

  4. Balance Oxygen atoms by adding H2O to the side that needs O.

  5. Balance hydrogen by adding by adding H+ to the side that needs H

  6. Balance the charge by adding electrons to the side with more positive charge

  7. Make electrons gained equal to the electrons lost.

  8. Add the two half-reactions to get the overall equation.

  9. Add the same # of OH- as there are H+ to both sides of the equation

  10. Combine OH- and H+ to form H2O

  11. 10. Cancel any H2O that you can
• Balancing Redox Reactions in acidic or basic solutions


  • Example 1
  • Example 2: MnO4- (aq) + H2C2O4(aq) -> Mn2+(aq) + CO2(g)
  • Example 3: Zn(s) + NO3- (aq) -> Zn2+(aq)+ NO(g)
• Balancing Redox Reactions in acidic or basic solutions


  • Example 2: ClO- (aq) + CrO2- (aq) -> Cl- (aq) + CrO4 2- (aq)
  • Example 3: MnO2 (aq) + ClO3 - (aq) -> MnO4 - (aq) + Cl- (aq)