Question

Define the following terms:

(i) Mole fraction 

(ii) Molality 

(iii) Molarity 

(iv) Mass percentage.

Answer 1

(i) Mole fraction (X): The mole fraction of any component in a solution is the ratio of the number of moles of that component to the sum of the number of moles of all the components present in the solution. For a binary solution containing A and B, Mole fraction of A,

where n_A and n_B are the numbers of moles of components A and B respectively. 

(ii) Molality (m): Molality is the numberof moles of the solute dissolved in 1000 gms (1 kg) of the solvent. It B denoted by ‘m’ mathematically.

(iii) Molarity of a solution is defined as the number of moles of the solute dissolved per litre (or dm³) of solution. It is denoted by ‘M’ mathematically.

(iv) Mass fraction multiplied by 100 gives mass percentage. E.g.: mass percentage of A