1. Balancing Chemical Equations
What information could a correctly balanced chemical equation provide?

2. Chemical reactions obey the laws of conservation of mass, charge, and energy
The total mass of the reactants is the same as the total mass of the products.
The total charge of the reactants is the same as the total charge of the products.

3. An equation is correctly balanced if:
there are the same number of atoms of each element involved on both sides

4. Electrolysis of Water
Water  Hydrogen + Oxygen 2 2
H2O  H O2

5. Balancing by Inspection
Count the number of atoms on both sides
Find an element that is out of balance and fix it
Add/Change Coefficients until each element is balanced
NEVER change Subscripts 2 2
Na Cl2  NaCl

6. The coefficients of a correctly balanced chemical equation can tell you:
The number of atoms / molecules that react
The moles worth of atoms / molecules that react
The relative volumes of gases that react (if reactants and products are gases)