How to Balance a Chemical Equation

Introduction to Balancing a Chemical Equation

By selecting the right coefficient for every molecule that provides an equal number of each type of atoms on both sides of the equation.
However, a balanced equation should contain the smallest possible whole number coefficients.

Example: Burning of Methane in air

CH₄ + O₂ → CO₂ + H₂O This is an unbalanced equation
So, we need to balance the equation. To do that we look at the number of atoms of each kind in each side of the equation, and change their coefficients accordingly,

Balance the Equation
Type of atom	In	Out	What should be
C	1	1	none
H	4	2	2 out
O	2	3	1 in

So, the corresponding balanced equation is: CH₄ + 2O₂ → CO₂ + 2H₂O

Remark:
Symbols such as s (solid), l (liquid)and g (gas), may be used to show the physical state of the substance involved in the reaction.
Conditions such as heat (shown as Δ) maybe also shown on the right arrow.
CH_{4 (g)} + 2O_{2 (g)} →Δ CO_{2 (g)} + 2H₂O (g)

Exercise: Balance the following chemical reactions:

Exercise: Balancing Chemical Reactions

Check your answers here:
Solutions