Ncert Exercises & Solutions

Which of the following terms are unitless?

1. Molality

2. Molarity

3. Mole fraction

4. Mass per cent

(c, d)

Both mole fraction and mass per cent are unitless as both are ratios of moles and masses respectively.

Mole fraction = \frac{Number of moles of solute}{Number of moles of solution} = \frac{moles}{moles}

= \frac{Number of moles of solvent}{Number of moles of solution} = \frac{moles}{moles}

Mass per cent = \frac{Mass of solute in gram}{Mass of solution in gram} \times 100