How do you Calculate the Number of Molecules in a Substance

Answer: The molecular mass of an element is the sum of its constituent elements’ atomic masses. The atomic mass units are also used to denote this amount.

To determine the number of molecules in a substance.

The total number of atoms/molecules in a sample can be calculated by multiplying the number of moles by the Avogadro constant. This formula is worded as follows:

One mole of substance comprises 6.022×1023 atoms, according to his law, which stipulates that “equivalent volumes of different gases measured under the same conditions of temperature and pressure contain the same number of molecules.”

To determine the required number of molecules, first determine the molecular weight of the substance for one mole, then divide the molar mass value by the molecular mass, and multiply by the Avogadro constant.

Example:

To determine the quantity of sulphur (S8) molecules present in a solid sulphur of present in 16 g of solid sulphur of 16 g.

1 mole of solid sulphur (S8)=8×32 g=256

256 g of solid sulphur contains 6.022×1023 molecules.

Then, 16 g of solid sulphur contains =6.022×1023256=16 molecules =3.76375×1022 molecules.