How do you Calculate the Number of Moles? Explain with Example.

Answer: You can calculate the number of moles by dividing the mass of a substance by its molar mass.

To calculate the number of moles (n) of a substance, you can use the formula:

n= m/M​

Where:

• n is the number of moles.
• m is the mass of the substance in grams.
• M is the molar mass of the substance in grams per mole.

For example, let’s say you have 36 grams of water (H₂O) and want to find the number of moles. The molar mass of water is the sum of the molar masses of its components: 2 hydrogen atoms (H) and 1 oxygen atom (O). The molar mass of hydrogen is approximately 1 g/mol, and oxygen is approximately 16 g/mol.

So, for water (H₂O): M= (2×1g/mol) + (1×16g/mol) = 18g/mol

Now, we use the formula :

n = m/M ​= 36g​ ÷1 8g mol= 2moles

So, we have 2 moles of water. This method is essential in chemistry for measuring substances in terms of moles, which allows for precise calculations in chemical reactions and stoichiometry.