Mole Fraction, Molality, Molarity

Mole Fraction

For a binary mixture (having component A and B); if the No. of moles of A and B are n_A and n_B respectively.

Mole fraction of A will be

Mole fraction of B will be

• n_A + n_B = 1 (sum of all the mole fraction is unity)

Molarity [M]

It is defined as number of moles of Solute dissolved in 1 Liter of Solution. It's SI uint is Mol/L.

Molality [m]

It is defines as  number of moles of the Solute dissolve in 1 Kilogram of  Solvent. It's SI unit is mol/Kg.

Advantage of Molality over molarity

Molality does not change with change in temperature while, Molarity decreases with rise in temperature. This is beacuse volume depends on temperature Volume is dieactly proportional to Temperature. (V α T) But Mass does not change.