1. II. Balancing Equations

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

3. B. 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”

4. C. Balancing Example Al + CuCl2  Cu + AlCl3 Al Cu Cl 1 1 
Aluminum and copper(II) chloride react to form copper and aluminum chloride.
Al CuCl2  Cu AlCl3 Al Cu Cl 

5. Evidence of chemical change

6. All chemical reactions
have two parts
_____________- the substances you start with
______________- the substances you end up with
The reactants turn into the products.
______________ ® _____________

7. Balanced Equation Atoms can’t be ________________ or _________________
All the atoms we start with we must end up with
A balanced equation has the same number of each element on both sides of the equation.

8. ® O + C O C O O ________ + _______ ® ________
__________________________
What if it isn’t already?

9. ® O + C C O O ___________+ ______ ® _________
We need one more oxygen in the products.
Can’t change the formula, because it describes what is

10. Never Change a subscript to balance an equation.
If you change the formula you are describing a different reaction.
H2O is a different compound than H2O2
Never put a coefficient in the middle of a formula
2 NaCl is okay, Na2Cl is not.

11. Example
H2 + O2
H2O
Make a table to keep track of where you
are at

12. Examples AgNO3 + Cu ® Mg + N2 ® P + O2 ® Na + H2O ® CH4 + O2 ®
Pb(NO3)2+ KI 
Show your work on a separate sheet of paper

13. On a separate sheet of paper balance the equations
Don’t Break the Law