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Question
Which of the following terms are unitless?
(i) Molality
(ii) Molarity
(iii) Mole fraction
(iv) Mass percent
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Solution
(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.
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