Mastering Balancing Chemical Equations: Step-by-Step Examples

Balancing chemical equations is a fundamental skill in chemistry, essential for understanding reactions and stoichiometry. This guide provides clear, practical examples to help you grasp the concept of balancing equations effectively.
By Jamie

What is a Chemical Equation?

A chemical equation represents a chemical reaction, showing the reactants (starting substances) and products (substances formed). Balancing these equations ensures that the law of conservation of mass is upheld, meaning that the number of atoms for each element is the same on both sides of the equation.

Steps for Balancing Chemical Equations:

  1. Write the unbalanced equation.
  2. Count the number of atoms of each element on both sides.
  3. Add coefficients to balance the atoms one element at a time.
  4. Double-check that all elements are balanced.

Example 1: Combustion of Methane

Unbalanced Equation:
CH₄ + O₂ → CO₂ + H₂O

Balancing Steps:

  1. Count atoms:
  • Left: C=1, H=4, O=2
  • Right: C=1, H=2, O=3

  1. Balance Hydrogen:

    • Add a coefficient of 2 to H₂O:
      CH₄ + O₂ → CO₂ + 2H₂O

    • New count: Left: C=1, H=4, O=2; Right: C=1, H=4, O=4

  2. Balance Oxygen:

    • Add a coefficient of 2 to O₂:
      CH₄ + 2O₂ → CO₂ + 2H₂O

    • Final count: Left: C=1, H=4, O=4; Right: C=1, H=4, O=4

Balanced Equation:
CH₄ + 2O₂ → CO₂ + 2H₂O

Example 2: Reaction of Iron and Oxygen

Unbalanced Equation:
Fe + O₂ → Fe₂O₃

Balancing Steps:

  1. Count atoms:
  • Left: Fe=1, O=2
  • Right: Fe=2, O=3

  1. Balance Iron:

    • Add a coefficient of 2 to Fe:
      2Fe + O₂ → Fe₂O₃

    • New count: Left: Fe=2, O=2; Right: Fe=2, O=3

  2. Balance Oxygen:

    • Add a coefficient of 3/2 to O₂ (or 3 to all coefficients):
      4Fe + 3O₂ → 2Fe₂O₃

    • Final count: Left: Fe=4, O=6; Right: Fe=4, O=6

Balanced Equation:
4Fe + 3O₂ → 2Fe₂O₃

Example 3: Decomposition of Water

Unbalanced Equation:
H₂O → H₂ + O₂

Balancing Steps:

  1. Count atoms:
  • Left: H=2, O=1
  • Right: H=2, O=2

  1. Balance Oxygen:

    • Add a coefficient of 2 to H₂O:
      2H₂O → H₂ + O₂

    • New count: Left: H=4, O=2; Right: H=2, O=2

  2. Balance Hydrogen:

    • Add a coefficient of 2 to H₂:
      2H₂O → 2H₂ + O₂

    • Final count: Left: H=4, O=2; Right: H=4, O=2

Balanced Equation:
2H₂O → 2H₂ + O₂

By following these steps and practicing with various equations, you can become proficient in balancing chemical equations. Remember, practice makes perfect!