1. Chemical Reactions & Equations
Chapter 8
Suggested Reading
Pages

2. Chemical Reaction
A process in which one or more substances are converted into new substances with different physical and chemical properties.

3. Reactants Products
Reactant or Reagent – a substance that enters into a chemical reaction.
Product – a substance that is produced by a chemical reaction.

4. Word Equations Read: Calcium reacts with oxygen to produce
Oxide
Calcium + Oxygen
Read:
Calcium reacts with oxygen to produce
calcium oxide

5. Balancing Chemical Equations
The number of atoms of each element MUST be the same before and after a chemical reaction.

6. Coefficients
Whole numbers placed in front of the formula to balance the number of atoms on each side of the equation.

7. Formula Equations Unbalanced: Ca + O2 CaO 2Ca + O2 2CaO Coefficients

8. Coefficient  subscript = # of atoms
Balancing Steps
1. Write the unbalanced equation.
2. Count atoms on each side.
3. Add coefficients to make numbers equal.
Coefficient  subscript = # of atoms
4. Reduce coefficients to lowest possible ratio, if necessary.
5. Double check atom balance.

9. Helpful Tips Balance one element at a time.
Update ALL atom counts after adding a coefficient.
If an element appears more than once per side, balance it last.
Balance polyatomic ions as single units.
“1 SO4” instead of “1 S” and “4 O”

10. Example 2 Al + CuCl2  Cu + AlCl3 Al Cu Cl 3 3 2 2  1 1 2 3  2  6
Aluminum and copper(II) chloride react to form copper and aluminum chloride. 2
Al CuCl2  Cu AlCl3 Al Cu Cl 3 3 2
2 
 2
 6
3 
6 
 3