Worksheet: Balancing Equations I. Fill in the blanks with the most appropriate term:
A tells the story of a chemical reaction. are the starting substances in the reaction while are the new substances that are formed. The large numbers in front of some of the formulas are called . These numbers are used to the equation because chemical reactions must obey the Law of of Matter. The number of atoms of each element on both sides of the equation must be because matter
cannot be or . When balancing equations, the only numbers that can be changed are ; remember that must never be changed in order to balance an equation.
II. Balance the following equations:
1. Al + O2 Al2O3

2. C3H8 + O2 CO2 + H2O

3. P4 + O2 P2O3

4. KNO3 KNO2 + O2

5. O2 + CS2 CO2 + SO2

6. KClO3 KCl + O2

7. N2 + H2 NH3

8. NaF + Br2 NaBr + F2

9. Al + HCl H +AlCl3

10. WO3 + H2 W + H2O