One chemical reaction is called the Haber process, a method for preparing ammonia by reacting nitrogen gas with hydrogen gas:
This equation shows you what happens in the reaction, but it doesn’t show you how much of each element you need to produce the ammonia. To find out how much of each element you need, you have to balance the equation — make sure that the number of atoms on the left side of the equation equals the number of atoms on the right.
You know the reactants and the product for this reaction, and you can’t change them. You can’t change the compounds, and you can’t change the subscripts, because that would change the compounds.
So the only thing you can do to balance the equation is add coefficients, whole numbers in front of the compounds or elements in the equation. Coefficients tell you how many atoms or molecules you have.
For example, if you write the following, it means you have two water molecules:
Each water molecule is composed of two hydrogen atoms and one oxygen atom. So with two water molecules (represented above), you have a total of 4 hydrogen atoms and 2 oxygen atoms.
You can balance equations by using a method called balancing by inspection. You take each atom in turn and balance it by adding appropriate coefficients to one side or the other.
With that in mind, take another look at the equation for preparing ammonia: HOPE THIS HELPS