Balancing Equations

1. Ch. 8 – Chemical Reactions Balancing Equations

2. 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 Aluminum and copper(II) chloride react to form copper and aluminum chloride. 2 3 3 2  2  6 1 1 1 1 2 3 2  3  6   3

5. Balance the following equations: 3 3 2 1.) Fe2O3 + H2 Fe + H2O 2 1 3 1 2 2 Fe O H  2  3 6   6

6. 2 2 2.) AgNO3 + H2S  Ag2S + HNO3 1 2 1 1 2 1 1 1 Ag NO3 H S 2  2   2  2

7. Problems (cont.) 3.) Zn(OH)2 + H3PO4 Zn3(PO4)2 +H2O 4.) SO2 + O2  SO3 5.) MnO2 + HCl  MnCl2 + H2O + Cl2