Review of Redox Reactions

• A half-reaction shows either a reduction or an oxidation reaction but not both
• reduction is a gain in electrons so that electrons are on the reactant side while oxidation is a loss of electrons so that electrons are on the product side
• What two things do we balance in a redox reaction?

  In a redox reaction, we balance both matter and charge
• What substances do you use to balance a reaction in an acidic medium?

  In an acidic medium, we add H+ and H2O in to balance the equation.
• What is a better technique in balancing reactions in basic medium?

  It is generally easier to balance reactions in basic medium by balancing it first as if it were in acidic medium. Then the H+ is neutralized by adding OH– in both sides of the equation. The number of H2O molecules in the overall equation is then adjusted.
• To balance the redox equation, you need to remember

  1. The number of each type of atom in both sides of the equation should be balanced.
  2. The total number of electrons lost or gained should be the same for both half-reactions.
• An oxidation-reduction reaction (redox reaction) is a chemical reaction wherein the oxidation number of a molecule, atom, or ion changes due to gain or lose of electrons
• the substance that loses an electron

  Oxidized substance
• the substance that gains an electron

  Reduced substance
• A reducing agent loses electrons and its oxidation state increases.
• A oxidizing agent gains electrons and its oxidation state decreases
• The substance oxidized is the reducing agent while the substance reduced is the oxidizing agent