How to Balance Chemical Equations: Complete Guide

Balancing chemical equations is a fundamental skill in chemistry. Here's exactly how to do it:

What Does "Balanced" Mean?

A balanced chemical equation has equal numbers of each type of atom on both sides, following the Law of Conservation of Mass.

Step-by-Step Method

Step 1: Write the Unbalanced Equation

Example: H₂ + O₂ → H₂O (unbalanced)

Step 2: Count Atoms on Each Side

Left side: 2 H, 2 O
Right side: 2 H, 1 O
Oxygen is unbalanced!

Step 3: Balance One Element at a Time

Start with the most complex molecule (H₂O):
- We need 2 oxygen atoms on the right
- Add coefficient 2: H₂ + O₂ → 2H₂O

Step 4: Recount and Adjust

Left side: 2 H, 2 O
Right side: 4 H, 2 O
Now hydrogen is unbalanced!

Step 5: Balance Remaining Elements

Add coefficient 2 to H₂: 2H₂ + O₂ → 2H₂O

Step 6: Final Check

Left side: 4 H, 2 O
Right side: 4 H, 2 O ✓ BALANCED!

More Complex Example

Unbalanced: C₃H₈ + O₂ → CO₂ + H₂O

Step 1: Count atoms
- Left: 3 C, 8 H, 2 O
- Right: 1 C, 2 H, 3 O

Step 2: Balance carbon first
C₃H₈ + O₂ → 3CO₂ + H₂O

Step 3: Balance hydrogen
C₃H₈ + O₂ → 3CO₂ + 4H₂O

Step 4: Balance oxygen
- Right side now has: (3$\times$2) + (4$\times$1) = 10 oxygen atoms
- Need 5 O₂ molecules: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

Final check:
- Left: 3 C, 8 H, 10 O
- Right: 3 C, 8 H, 10 O ✓

Pro Tips

1. Balance metals first, then non-metals, then hydrogen and oxygen last
2. Use fractions if needed, then multiply everything to get whole numbers
3. Never change subscripts - only add coefficients
4. Start with the most complex molecule
5. Double-check your work by counting atoms

Common Mistakes to Avoid

❌ Changing subscripts (H₂O → H₃O)
❌ Adding elements not in the original equation
❌ Forgetting to multiply coefficients by subscripts
❌ Not checking your final answer

Practice Problems

Try these:
1. Fe + O₂ → Fe₂O₃
2. NH₃ + O₂ → NO + H₂O
3. C₂H₆ + O₂ → CO₂ + H₂O

Answers:
1. 4Fe + 3O₂ → 2Fe₂O₃
2. 4NH₃ + 5O₂ → 4NO + 6H₂O
3. 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O

With practice, balancing equations becomes automatic!