1. 7.4 BALANCING A CHEMICAL EQUATION By: Faraz, Reilly, Matt

2. DEFINITION balancing equations- each side of the equation has the same number of atoms of each element. REMEMBER- in a chemical reaction, atoms are not created or destroyed, they are simply rearranged. Coefficient – a small whole number that appears in front of a chemical formula in a equation.

3. RULES 1.Determine the correct formulas for the product and reaction. 2.Write the formulas for the reactants on the left and the product on the right with a yield sign in between them. If two or more reactants or products are involved, separate there formulas with + signs. PbO ₂ PbO + O ₂ MgO + H 2 O Mg(OH) ₂

4. RULES 3.Count the number of atoms of each element in the reactants and products. A polyatomic ion unchanged on both sides of the equation is counted as 1 unit. PbO ₂ PbO + O ₂ 1+2 1+3

5. RULES 4. Balance the elements one at a time by using coefficients. When no coefficient is there it is assumed to be 1. It is best to begin the balancing operation with elements that appear only once on each side of the equation. DON’T change the subscripts. P + 0 ₂ P ₄ O ₁₀ 4P + 5O ₂ P ₄ O ₁₀

6. RULES 5. Check each atoms or polyatomic ion to make sure that each equation is balanced. 6. Finally make sure the coefficients are in simplest form. KEEPING the same ratio. 8P + 10 O ₂ 2P ₄ O ₁₀ (what not to do) 4P + 5O ₂ P ₄ O ₁₀

7. PRACTICE PROBLEMS Al + N ₂ AlN Al + N₂ 2AlN 2Al + N ₂ 2AlN

8. PRACTICE PROBLEM Carbon + Oxygen Carbon Dioxide C + O ₂ Carbon Dioxide C + O CO ₂

9. HOMEWORK Balance These Na + Br ₂ NaBr Iodine + Fluorine Pentiodine Difluoride