Balancing Chemical Equations

Terms Subscript: Coefficient:

RULES YOU CAN ONLY ADD WHOLE MOLECULES!!!! This means you can only change coefficients, never subscripts.

Step 1: Identify the Reactants and Products Reactants: Products:

Step 2: Write a word equation for the reaction General Formula: Example:

Step 3: Rewrite the equation using formulas for the elements and compounds Remember: some gaseous elements, like Oxygen, are molecules (O 2 ), not atoms Example: Magnesium + oxygen  magnesium oxide

Diatomic Elements

Step 4: Balance the equation one element at a time The same number of each kind of atom must appear on both sides. So far, there is one atom of magnesium on each side of the equation Mg + O 2  MgO AtomReactantsProductsBalanced? Mg O

Step 4: Balance the equation one element at a time But there are two oxygen atoms on the left and only one on the right. To balance the number of oxygen atoms, you need to double the amount of magnesium oxide Mg + O 2  2MgO AtomReactantsProductsBalanced? Mg O

Step 4: Balance the equation one element at a time This equation gives you two magnesium atoms on the right and only one on the left, so you need to double the amount of magnesium on the left as follows. 2Mg + O 2  2MgO AtomReactantsProductsBalanced? Mg O

Homework