Oxidation Reduction Reactions AKA Redox Reactions So far we have balanced reactions so that the number of each element in the reactants and products is the same. - Now we are going to also balance reactions so that atoms will lose and gain electrons and the number of electrons lost and gained will be the same.

Oxidation Reduction Reactions Oxidation: The loss of electrons in a chemical reaction Reduction: The gain of electrons in a chemical reaction http://www.youtube.com/watch?v=e6Xxz-VBE6s

Oxidation – Reduction Reaction or Redox Reaction - When one reactant loses electrons and another gains a electrons in a reaction In a redox reaction oxidation and reduction happen simultaneously

L E O oses lectrons xidation G E R ains lectrons eduction A trick to remembering which element is being oxidized and which one is being reduced L E O oses lectrons xidation G E R ains lectrons eduction

Reducing Agent: - The reactant in a redox reaction that loses electrons - It makes the other reactant reduced Oxidizing Agent: The reactant in a redox reaction that accepts electrons - It makes the other reactant oxidized Oxidation Number: - The charge on an ion

+3 -2 +2 -2 0 +4 -2 Fe2O3 + CO → Fe + CO2 How to: Identify the charges for every element in the reactants and in the products. - Hint: if two nonmetals are bound together, the nonmetal that is most electronegative will have its usual negative charge. The other atom will have whatever charge is necessary for the compound to add up to zero total charge.

+3 -2 +2 -2 0 +4 -2 Fe2O3 + CO → Fe + CO2 Now you can write the Half Reactions - Half Reactions are a mini chemical equation that shows how one atom changes it charge (because of gaining or losing electrons) from the reactants to the products. For the equation above: Fe+3 + 3e-  Fe0 C+2  C+4 + 2e-

+3 -2 +2 -2 0 +4 -2 Fe2O3 + CO → Fe + CO2 Now you can identify which element is oxidized and which one is reduced. - Fe is gaining negative electrons and is reduced - C is losing negative electrons and is oxidized.

+3 -2 +2 -2 0 +4 -2 Fe2O3 + CO → Fe + CO2 You can also identify what the oxidizing agent and reducing agent are. - Fe is forcing C to lose electrons so that it can gain those electrons. This means that Fe is the oxidizing agent - C is forcing Fe to gain electrons so that it can lose those electrons. This means that C is the reducing agent.

+3 -2 +2 -2 0 +4 -2 3 2 3 Fe2O3 + CO → Fe + CO2 You can use the half reactions that you already wrote to balance difficult reactions. According to the half reactions; Fe+3 + 3e-  Fe0 and C+2  C+4 + 2e- Each C atom loses 2 electrons and each Fe atom gains 3 electrons. - the least common multiple of 2 and 3 is 6 - this means that we should add coefficients to both the reactants and products so that we have enough C and Fe atoms to lose 6 electrons and gain 6 electrons respectively - Now go through and add coefficients to finish balancing if necessary

+3 -2 +2 -2 0 +4 -2 Fe2O3 + 3 CO  2 Fe + 3 CO2 Now you can identify how many electrons are exchanged (transferred or traded between different types of atoms). According to the half reaction, C+2  C+4 + 2e- each carbon atom loses two electrons. In the balanced reaction there are three carbon atoms - this means that there are a total of 6 electrons given off by all the carbon atoms According to the half reaction, Fe+3 + 3e-  Fe0 each iron atom gains three electrons. In the balanced reaction there are two iron atoms - this means that there are a total of 6 electrons gained by all the iron atoms The 6e- lost by the C atoms are the same 6e- gained by the Fe atoms In other words there are 6e- exchanged in the balanced reaction

+3 -2 +2 -2 0 +4 -2 Fe2O3 + 3 CO  2 Fe + 3 CO2 Spectator Ion: a spectator ion is an ion in the reaction that does not change its charge from the reactants to the products. - In this reaction, O has a -2 charge in both the reactants and the products so it is the spectator ion

When transition elements gain and lose electrons in chemical reaction they can be used to make a cell or battery.

When electricity (or electrons) are added in a setup similar to a battery you can electroplate metal onto another metal.