Balancing a Chemical Equation

The number of atoms on each side of a chemical equation must be equal.

To balance a chemical equation the following rules must be followed:

-After you have written a chemical equation check to see if the equation is balanced (have the same number of atoms of each element on each side).

-If it is not balanced then the smallest possible number must be placed in front of the reactants and/or products to ensure it is balanced on either side.

Let’s look at the following equations:

C(s) + O2 (g) CO2 (g)

The equation above is balanced as you can see there are an equal number of carbon and oxygen atoms on either side.

H2 (g) + O2 (g) →   H2O (l)

This equation above is not balanced. Let’s look at the left and right sides of the equation and count the number of hydrogen and oxygen atoms. There are 2 hydrogen atoms and 2 oxygen atoms on the left side of the equation and there are 2 hydrogen atoms and one oxygen atom on the right side.

If we follow the rules from above, we must add the smallest possible number in front of the products and/or the reactants to ensure it is balanced on either side.

The balanced equation is:

2H2 (g) + O2 (g) 2H2O (l)

Here is another example:

Fe(s) + Cl2 (g) FeCl3(s)

The equation above is not balanced.

The balanced equation looks something like this:

2Fe(s) + 3Cl2(g) 2FeCl3(s)

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