Question

Which of the following terms are unitless?

(i) Molality

(ii) Molarity

(iii) Mole fraction

(iv) Mass percent

Answer 1

(iii) Mole fraction

(iv) Mass percent

Explanation:

Molality: It is defined as the number of moles of solute divided by the mass of solution in kg. It is denoted by m. The formula is expressed as 

m = `n/W`

The \[\ce{Sl}\] unit of morality is mol kg^–1.

Molality: It is defined as the number of moles of solute divided by the volume of solution in latice. It is represented by M. The formula of molarity is expressed as 

M = `n/V`

Here, n is the number of moles of solute and V is the volume of solution expressed in litres. The \[\ce{Sl}\] unit of molarity is mol L^–1.

Mole fraction (x): The mole fraction of a substance is defined as the number of moles of that substance divided by the total number of moles of all substances present in the solution.

Mass percent: it is defined as the weight of the solute divided by the total weight of the solution and the obtained result is multiplied by 100 in order to give a percent.

Thus, mole fraction and mass percent are unitless.