1. (2.3) Balancing Chemical Equations (p150)

2. Conservation of Mass As we saw in class, the mass of the reactants must equal the mass of the products in a chemical reaction. To show that a reaction is balanced, we must write a balanced chemical equation. In a balanced chemical equation, the number of atoms on each side of the equation is the same.

3. How To Write a Balanced Chemical Equation 1. The chemical formula for a substance CANNOT be changed! ex. CO 2 molecules must stay as CO 2

4. How To Write a Balanced Chemical Equation 2. From the word equation, write the chemical equation using the correct chemical formula for all the substances involved. ex. The combustion of ethanol (C 2 H 6 OH) ethanol+ oxygen  carbon dioxide + water C 2 H 6 OH + O 2  CO 2 + H 2 O

5. How To Write a Balanced Chemical Equation 3. Count the number of atoms in both the reactants and products. 4. Multiply each formula by a coefficient to balance the number of each kind of atom in both the reactants and products.

6. THE RAP SHEET The RAP sheet is a methodology used to help balance chemical equations. It helps keep track of the number and kinds of atoms in a chemical equation.

7. R Reactants A Atoms P Products C H O 2 6 3 C 2 H 5 OH + O 2  CO 2 + H 2 O Add coefficient 2 CO 2 Add coefficient 3 to H 2 O Add coefficient 3 to O 2 1 2 3 2 5 6 7 7

8. TRY THESE Worksheets 2.3 (D) and 2.3 (E)

9. (2.3) Balancing Chemical Equations (p150)

10. ASSIGNMENTS: Workbook p56 p60-63