Balancing chemical equations

Atoms can neither be destroyed nor created during a simple chemical reaction. Therefore, in a chemical reaction

The sum of atoms before reaction = the sum of atoms after reaction

General Rules for balancing chemical equations – Rule 2

Balancing chemical equations may require some trial and error. There are some general rules that could be helpful, but they may not work all the time.

• Rule 1: Balancing chemical equations using the one’s and two’s technique
• Rule 2: Balancing chemical equations using the two’s and three’s technique
• Rule 3: Balancing chemical equations using the CHO technique
• Rule 4: Balancing chemical equations using the even technique
• Rule 5: Balancing chemical equations containing polyatomic ions

In this page, we will look at some examples of applying

Rule 2: Balancing chemical equations using the two’s and three’s technique.

Example:

Balance the equation

Fe + O₂ → Fe₂O₃

Solution:

Step 1: On the left side of the equation there are 2 oxygen atoms and on the right side of the equation there are 3 oxygen atoms. To balance the oxygen atoms, multiply Fe₂O₃ by the coefficient of 2 and the O₂ by the coefficient of 3

Fe + 3O₂ → 2Fe₂O₃

Step 2: Balance the Fe by placing the coefficient of 4 in front of Fe

4Fe + 3O₂ → 2Fe₂O₃

Step 3: Check that all the atoms balance and make sure that all coefficients are in the lowest-possible ratio.

The following videos show some examples of using the two’s and three’s method to balance chemical equations.

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