Mole:

Mole can be defined as amount of the substance that contains as many particles or entities or atoms exactly in 12 gm of the C-12 isotope.

1 atom of  C-12 weighs ———1.99×10^-23gm

How may atoms will be in——12 gm

Therefore 12×1/1.99×10^-23=6.023×10²³atoms.

These number of atoms in c-12 isotope can be mentioned as Avagadro number of atoms.

1 mole of any substance consists of avagadro number of atoms/molecules/ions i.e;6.023×10²³atoms/molecules/ions.

Avagadro number is indicated with capital letter ‘N’

N value is 6.023×10²³atoms/molecules/ions.

For example:

1 mole of H₂O molecule consists of  N number of water molecules.

1 mole of H₂O molecule consists of  2N number of  hydrogen atoms.

1 mole of H₂O molecule consists of 1N number of oxygen atoms.

Molar mass:

Molar mass can be defined as mass of  1 mole of substance in grams.

For example: 1 mole of H₂O weighs 18gm.

1 mole of CO₂ weighs 44gm.

Percentage composition:

Generally the molecule is made of atoms.if we consider the molecule is 100% then we should find the percentage composition of individual atoms or elements in the given molecule or compound.

For example:

Lets find the percentage composition of hydrogen and oxygen in water molecule.

Total is 99.9% which is nearly equal to 100%.