Balancing redox reactions

The electrons that are lost by the reducing agent are the same as the electrons gained by the oxidizing agent in a redox reaction. This means that in a redox reaction in addition to balancing the number of atoms for each element, the number of electrons also needs to be balanced.

In order to balance a redox reaction in an aqueous environment, it is important to first determine whether the environment is acidic or alkaline. Depending on the environment, H2O, H+ and/or OH- water, a proton, and or an hydroxide group should be added to the reaction.

In an acidic environment, the steps to balance the reaction are:

  1. Find the half-reactions
  2. Balance all atoms except O and H oxygen and hydrogen
  3. Balance oxygen by adding H2O water
  4. Balance hydrogen by adding H+ a proton
  5. Balance the charges by adding e- an electron
  6. Balance e- an electron and add up the half-reactions

In an alkaline environment, the steps to balance the reaction are:

  1. Find the half-reactions
  2. Balance all atoms except O and H oxygen and hydrogen
  3. Balance oxygen by adding H2O a molecule of water
  4. Balance hydrogen by adding H+ a proton
  5. Balance the charges by adding e- an electron
  6. Neutralize H+ by adding OH- a proton by adding an hydroxide group
  7. Balance H+, OH-, and e- a proton, an hydroxide group and an electron and add up the half-reactions