Summary of Unit 5: Electrochemistry Oxidation numbers help to determine which element is being oxidized and which is being reduced in a given chemical reaction. The element being reduced is the Oxidation Agent. Likewise, the element being oxidized is the Reducing Agent. In a chemical reaction, the oxidized and reduced elements can be deduced from the change in charge. Remember the acronym OIL RIG: Oxidation Involves Loss (of charge, electrons), Reduction Involves Gain (of charge, electrons). Balancing half reactions in a basic solution involves the same process as balancing in an acidic solution until the final, additional step that basic solution balancing requires. Recommended order in which to balance molecules in a half reaction: original ions, then water molecules, followed by Hydrogen ions, then finally balance the charge in the reaction by adding electrons to a given side. Don’t forget to cancel out similar molecules, elements, or ions on opposite sides of a reaction after combining two half reactions. Always simplify! In an electrochemical cell, the anions of the salt bridge will always travel in the opposite direction of the electrons. When comparing two reduction equations in a cell, the equation with a smaller voltage value is the reaction that will go in the reverse direction (be oxidized instead of reduced). Don’t forget to flip the sign on the voltage of the oxidation reaction. Corrosion is when one metal is oxidized away due to a chemical reaction with its surroundings. Remembering Conversion Factors in Electrochemistry: Charge, q, is represented in units of Coulombs (C). Current, I, (also known as “amperage”) is in the unit of Amperes, or Coulombs per second. Voltage, E, (also referred to as potential, emf) is in the unit of Volts, or Joules per Coulomb. Power, P, is represented by the unit Watts, or Joules per second. Energy is given in the units of Joules.