Five ways of calculating the number of molecules of a chemical compound

As a chemistry student, you have to know how to calculate the number of molecules of a particular chemical compound. However, sometimes most students fail to get the correct way of calculating molecules of a chemical compound. 

In this post, I will show you five remarkable ways of calculating the number of molecules of a chemical compound. Though, before I do that you have to understand the mole concept? What is a mole in chemistry? In chemistry, a mole is defined as the quantity unit that represents the amount of a particular substance. 

In chemistry, one mole of any chemical compound consists of 6.022 X 10²³ molecules. The number 6.022 X 10²³ is referred to as the Avogadro’s constant. 

The following are the steps of calculating the number of molecules of a chemical compound: 

Step one:  know the chemical formula

You have to determine the chemical formula of a chemical compound you want to calculate its number of molecules. For instance, let consider potassium sulfate. K₂SO₄ is the chemical formula of potassium sulfate. Each molecule of potassium sulfate comprises two atoms of potassium (K), an atom of sulfur (S), and four atoms of oxygen (O). 

Step two: determine atomic weights of every element

You have to note down the atomic weight of each element in a chemical compound. In our case, the atomic weights of potassium (K), sulfur (S), and oxygen (O) are 40, 32 and 16 respectively. 

Step three: determine the atomic of the compound

To get the molar mass of the chemical compound, you have to multiply the atomic mass of each element by the number of atoms in the molecule, and then adding the obtained weights together. In our example, this is done as follows (K₂SO₄):

(40 X 2)+ (32 X 1) + (16 X 4) =136g/mole

Step four: determine the number of moles

To get the number of moles, you have to divide the known (given) mass by the molar of the chemical compound. For example, let say 30 grams of potassium sulfate is provided in our case. Therefore, the number of moles K₂SO₄ would be:

30 grams/ 136 grams/mole= 0.221 moles 

Step five: getting the number of molecules

The number of molecules is obtained by multiplying the number of moles by the Avogadro’s constant (6.022 X 10²³). Hence, the number of molecules of potassium sulfate will be: 

(0.221 moles X 6.022 X 10²³)= 1.331 X 10²³ molecules of potassium sulfate 

By following these steps, you can calculate the number of molecules of any chemical compound.