1. Information in Chemical Equations (Balancing)
Remember, the Law of Conservation of Mass states that atoms (mass) can’t be created or destroyed during a reaction. The same amount of each atom must be present in the reactants and products.
Example:
If 5g of hydrogen mix with 3g of oxygen, how much water would be produced?
Answer = 8g of water
Example:
If 16g of copper reacts with oxygen to produce 21.5g of copper oxide, how much oxygen was needed?
Answer = 5.5g of oxygen

2. We balance chemical equations so that they follow the law of conservation of mass.
The coefficients change the number of any given molecule in the equation.
The mass of the reactants will equal the mass of the products in a balanced equation.

3. STEPS TO BALANCE AN EQUATION:
1. Write the word equation.
2. Write the skeleton equation (unbalanced chemical formula).
3. Count the number of atoms in the reactants and products.
4. Multiply each formula by the correct coefficient to balance the number of atoms on each side of the equation. START with atoms that appear the least number of times and leave oxygen and hydrogen for the end.
5. Check the number of atoms on each side in the comparison table.

4. Balancing Equations
Example 1: Magnesium reacts with oxygen to produce magnesium oxide.
Write the word equation
Magnesium and Oxygen reacts to form Magnesium Oxide
Mg + O2 → MgO
Write the skeleton chemical equation
Count the number of each atom in the reactants and the products.
Reactants
Products Mg 1 O 2

5. Multiply the formulas by the correct coefficient
Multiply the formulas by the correct coefficient. Start with the atoms that appear the least number of times and leave oxygen and hydrogen until the end.
Reactants
Products Mg 1 O 2
Mg + O2 → MgO
Reactants
Products Mg 1 2 O
Mg + O2 → 2 MgO
Reactants
Products Mg 2 O
2 Mg + O2 → 2 MgO

6. Example: Methane and Oxygen react to form Carbon Dioxide and Water
_____ CH _____ O2  _____ CO _____ H2O
Check to see that the number of atoms in the reactants and products match.
Reactants
Products C H O

7. Example: Methane and Oxygen react to form Carbon Dioxide and Water
Reactants
Products C 1 H 4 2 O 3
CH4 + O2  CO2 + H2O
Reactants
Products C 1 H 4 O 2
CH4 + O2  CO2 + 2 H2O
Reactants
Products C 1 H 4 O
CH4 + 2 O2  CO2 + 2 H2O

8. Zinc + Silver nitrate  Zinc nitrate and Silver
Example: Zinc and Silver nitrate react to form Zinc nitrate and Silver.
Zinc + Silver nitrate  Zinc nitrate and Silver
_____ Zn + _____ Ag (NO3)  _____ Zn (NO3) _____ Ag
Check to see that the number of atoms in the reactants and products match.
Reactants
Products Zn 1 Ag N 2 O 3 6

9. Example: Zinc and Silver nitrate react to form Zinc nitrate and Silver.
Reactants
Products Zn 1 Ag N 2 O 3 6
Zn + Ag(NO3)  Zn(NO3)2 + Ag
Reactants
Products Zn 1 Ag 2 N O 6
Zn + 2 Ag(NO3)  Zn(NO3)2 + Ag

10. Reactants
Products Zn 1 Ag 2 N O 6
Zn + 2 Ag(NO3)  Zn(NO3)2+ 2 Ag

11. Now practice……..
Write a balanced equation for the reaction between potassium and bromine to make potassium bromide.
Write a balanced chemical equation for the reaction between oxygen and pentane (C5H12) to produce carbon dioxide and water.
Write a balanced chemical equation for the reaction between iron (III) nitrate and sodium hydroxide to produce iron (III) hydroxide and sodium nitrate.