A mole is the amount of a substance which contains the same number of chemical units (atoms, molecules or ions) as there are atoms in exactly 12 g of carbon-12. The unit of mole is given by the symbol ‘mol’.
We know that Avogadro number is 6.022 × 1023
Number of molecules in a certain mass
= (Mass of the substance / Molar mass) x NA
= (W / M) x 6.022 x 1023 molecules
where ‘W’ is the mass of the substance in which number of molecules is to be calculated and ‘M’ is the molecular mass of the substance.
