Chapter 18 – Electrochemistry
18.1 – Redox Reactions
• Electrochemistry is a branch of chemistry that deals with the conversions between electrical and
o Electrochemical processes are redox reactions.
The energy released from a spontaneous reaction is converted to electricity
Electrical energy is used to cause a non-spontaneous reaction to occur.
Balancing Redox Reactions
• The overall reaction is split into its half reactions. Then, the half reactions are balanced separately.
o First, all atoms other than O and H are balanced.
• If the reaction takes place under acidic conditions, H O mol2cules are added to balance the O atoms.
Then H are added to balance the H atoms. If the charges are not equal on both sides of the reaction,
electrons are added. Then, the half reactions are multiplied by whole numbers so that there are an equal
number of electrons in both reactions. Then, the half reactions are added, and electrons are cancelled.
• If the reaction takes place under basic conditions, the same steps as for acidic conditions are followed.
Then the same number of OH as the number of H present are added to both sides of the equation. The
OH combine with the H to form water (on one side of the equation). Then, H O are cancelled2on both
sides of the equation.