1. Writing Equations
Walkthrough

2. Example 1
1) The reaction of ammonia (NH3) with iodine to form nitrogen triiodide and hydrogen gas.
Step 1 – Write formulas out in words.
Ammonia Iodine  Nitrogen Triiodide Hydrogen Gas
Step 2 – Write symbols for the words:
NH I  N I H
Step 3 – Check for diatomic elements (BrINClHOF):
NH I  N I H2
Step 4 – Combine atoms into molecules/compounds:
NH I  NI H2
Step 5 – Balance:
2 NH I  NI H2
Step 6 – Classify:
SINGLE REPLACEMENT

3. Propane + Oxygen  Carbon Dioxide + Water
Example 2
2.) The combustion of propane (C3H8). This is a reaction of propane with oxygen that yields carbon dioxide and water.
Step 1 – Write formulas out in words (optional):
Propane Oxygen  Carbon Dioxide Water
Step 2 – Write symbols for the words:
C3H O  C O H2O
Step 3 – Check for diatomic elements (BrINClHOF):
C3H O2  C O H2O
Step 4 – Combine atoms into molecules/compounds:
C3H O2  CO H2O
Step 5 – Balance:
C3H O2  3 CO H2O
Step 6 – Classify:
COMBUSTION

4. Example 3 Step 1 – Write formulas out in words (optional):
aluminum bromide + magnesium hydroxide  aluminum hydroxide + magnesium bromide
Step 2 – Write symbols for the words:
Al Br Mg OH  Al OH Mg Br
Step 3 – Check for diatomic elements (BrINClHOF):
NONE
Step 4 – Combine atoms into molecules/compounds:
Al3+ Br Mg2+ OH  Al3+ OH Mg2+ Br -
AlBr Mg(OH)2  Al(OH) MgBr2
Step 5 – Balance:
2 AlBr Mg(OH)2  Al(OH) MgBr2
Step 6 – Classify:
Double Replacement