1. How to Balance Chemical Equations
By: Erin Lee

2. What Are Chemical Equations?
Chemical equations occur when bonds between the outermost parts of atoms are formed or broken.
Chemical equations involve changes in matter, the making of new materials with new properties, and energy changes.

3. Know Your Symbols! Solid (s) Liquid (l) Gas (g) Aqueous solution (aq)
Heated ()

4. The Set Up of an Equation
The molecules on the Left side of the arrow, are called the reactants.
The molecules on the Right side of the arrow, are called the products.
The “+” sign separates molecules on the same side
The arrow reads as “yields”
Example Problem: C + O2 --> CO2
- This reads Carbon plus oxygen yields carbon dioxide.

5. Rules of Balancing
Because of the principle of The Conservation of Matter,
an equation must be balanced.
It must have the same number of atoms of the same kind on both sides.
When balancing a chemical reaction you may add coefficients in front of the compounds to balance the reaction.
But you may not change the subscripts. Changing the subscript will change the compound.

6. The First Step in Balancing!
Write the correct formula for the reactants and the products.
Do not try to balance it yet. You must write the correct formulas first.

7. Second Step!
Find the number of atoms for each element on the left side. Then compare those against the number of the atoms of the same element on the right side.
Example: 2Al(s) + 3Br2(l) ---> Al2Br6(s)
Right Side Left Side
Al = 2 Al = 2
Br = 6 Br = 6

8. Step Three!
Determine where to place coefficients in front of formulas so that the left side has the same number of atoms as the right side for EACH element in order to balance the equation.
Example: ___ Al(s) + ___ Br2(l) ---> ___ Al2Br6(s)
Answer: ___ Al(s) + ___ Br2(l) ---> ___ Al2Br6(s) 2 3

9. Last But Not Least! Check Your Work!
The numbers of atoms on both sides of the equation are now balanced.
The coefficients are in the lowest possible whole number ratios. (reduced)