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
 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.