1. BALANCING CHEMICAL EQUATIONS H 2 + O 2 --> H 2 O

2. What is a chemical equation? H 2 + O 2 --> H 2 O Chemical equations are mathematical models to represent what happens with a chemical reaction. It helps to demonstrate the conservation of mass because the atoms in the reactants will be rearranged in various ways to create the products. No atoms will be created or destroyed in this process!

3. What is a chemical equation? H 2 + O 2 --> H 2 O In the chemical equation above, the substances to the left of the arrow are the “reactants.” These substances will react with each other. The substances to the right of the arrow are the “products.” These will be produced as a result of the chemical reaction

4. 1. Count the number of atoms of each element for the reactants and products. H 2 + O 2 --> H 2 O H H H H H H H H O O O O O O Reactants: H-2 atoms O-2 atoms Products: H-2 atoms O-1 atom This equation is NOT balanced! =

5. 2. Add coefficients to balance the atoms. H 2 + O 2 --> H 2 O H H H H H H H H O O O O O O Reactants: H-4 atoms O-2 atoms Products: H-4 atoms O-2 atom This equation IS balanced because there are 4 atoms of hydrogen on both sides and 2 atoms of oxygen on both sides. H H H H H H H H O O = 2 2

6. 2. Add coefficients to balance the atoms. 2H 2 + O 2 --> 2H 2 O H H H H H H H H O O O O O O The coefficients tell you the number of molecules you will need for this reaction to take place. You will need TWO molecules of H 2 and ONE molecule of O 2 to react, yielding TWO molecules of H 2 O H H H H H H H H O O =

7. N 2 + H 2 --> NH 3 H H H H H H H H H H N N N N N N = Reactants: Nitrogen-2 Hydrogen-2 Products: Nitrogen-2 Hydrogen-6 H H H H H H N N 2 Not balanced yet

8. N 2 + H 2 --> NH 3 H H H H H H H H H H N N N N N N = Reactants: Nitrogen-2 Hydrogen-6 Products: Nitrogen-2 Hydrogen-6 H H H H H H N N 2 3 H H H H H H H H Balanced!

9. Fe + O 2 --> Fe 2 O 3 Fe O O O O O O O O O O Reactants: Iron-1 Oxygen-2 Products: Iron-2 Oxygen-3

10. Fe + O 2 --> Fe 2 O 3 Fe O O O O O O O O O O Reactants: Iron-1 Oxygen-2 Products: Iron-4 Oxygen-6 2 Fe O O O O O O

11. Fe + O 2 --> Fe 2 O 3 Fe O O O O O O O O O O Reactants: Iron-4 Oxygen-2 Products: Iron-4 Oxygen-6 2 Fe O O O O O O 4

12. Fe + O 2 --> Fe 2 O 3 Fe O O O O O O O O O O Reactants: Iron-4 Oxygen-6 Products: Iron-4 Oxygen-6 2 Fe O O O O O O 4 3 O O O O O O O O Balanced!