In chemistry, the Mole is used as a fundamental unit that helps us understand the world at the atomic and molecular level. But what exactly is a Mole, and why is it so important in chemistry?
A mole is a unit of measure used to indicate a specific amount of substance. Basically, it’s a way of talking about atoms, molecules, or other chemical entities in terms that are tractable on a human scale. The definition of a mole is linked to the number of carbon atoms in exactly 12 grams of pure carbon-12. This corresponds to 6.022×10 23 particles. This gigantic number, known as the Avogadro number , provides a bridge between the microscopic world of atoms and molecules and the macroscopic world in which we live.
How to calculate the number of moles of a substance is explained step by step below. We have also added a handy Mol calculator with which you can check your calculation.
Step 1: Calculate the molecular mass
To calculate the molecular mass of a molecule you need the molecular formula. Imagine you have the following substance:
Sodium hydroxide
Molecular formula: NaOH
Then determine the elements that make up the molecule and determine the number of atoms and the atomic mass of each element. In the case of the substance sodium hydroxide have the following:
- 1 sodium atom (Na) with atomic mass 22.990 u
- 1 oxygen atom (O) with atomic mass 15.999 u
- 1 hydrogen atom (H) with atomic mass 1.008 u
Then add all the masses together:
(1 x 22.990 h) + (1 x 15.999 h) + (1 x 1.008 h) = 39.997 h
So the molecular mass of sodium hydroxide is 39.997 u.
Step 2: Convert Grams to Moles
In the example of sodium hydroxide, we have a molecular mass of 39.997 u. According to de Mol’s definition, this means that 39.997 grams of sodium hydroxide is equal to 1 mole.
39.997 grams NaOH = 1 Mole
Imagine we have 100 grams of Sodium Hydroxide. To convert this to the Mole unit, we divide 100 grams by 39.997.
100 grams / 39.997 h = 2.50 Mole
You can use the mole calculator below to calculate the number of moles for other substances.
Tips and other useful tools
Always proceed step by step and break down the molecular formula into the elements that make it up. Write down each step and make an ordered list of each element and its associated atomic mass. Do the calculation and use the calculator on this page to check your calculation.
Do you want to calculate the molarity of a solution? Then you can use our molarity calculator by following the link below.
