A molecule is the smallest particle of a substance (element or compound) which is capable of independent existence and shows all the properties of that substance. A molecule may be regarded as a group of two or more atoms that are chemically bonded together.

Atomic mass of an atom is defined as 1 12 th of the mass of carbon- 12 atom. In other words, atomic mass expresses the number of times an atom of the element is heavier than a carbon atom whose atomic mass is taken as 12 u .

Calculate the molar mass of Sulphuric acid, H 2 SO 4 .

The gram atomic mass of sulphur= 32 g , The gram atomic mass of hydrogen= 1 g , The gram atomic mass of oxygen= 16 g . The molar mass of H 2 SO 4 = ( 2 × Gram atomic mass of H ) + Gram atomic mass of S + ( 4 × Gram atomic mass of O ) . The molar mass of H 2 SO 4 = 2 × 1 + 32 + ( 4 × 16 ) = 98 g .