7.4 BALANCING A CHEMICAL EQUATIONBy: Faraz, Reilly, Matt

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.

RULES1. 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.

PbO₂ PbO + O₂ MgO + H2O Mg(OH)₂

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.

PbO₂ PbO + O₂

1+2 1+3

RULES4. 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 + 0₂ P₄O₁₀

4P + 5O₂ P₄O₁₀

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 + 10O₂ 2P₄O₁₀ (what not to do)

4P + 5O₂ P₄O₁₀

PRACTICE PROBLEMS

Al + N₂ AlN Al + N₂ 2AlN2Al + N₂ 2AlN

PRACTICE PROBLEM

Carbon + Oxygen Carbon DioxideC + O₂ Carbon DioxideC + O CO₂

HOMEWORK Balance These Na + Br₂ NaBr Iodine + Fluorine Pentiodine Difluoride