WAEC Chemistry 2020 Paper

Concept:A molar quantity is a physical property expressed per amount of substance, that is, per mole.Explanation:Molar mass is the mass present in one mole of a substance.It is defined by the relation $M = \frac{m}{n}$, where $m$ is mass and $n$ is the amount in moles.Its unit is $\mathrm{g\,mol}^{-1}$, which directly shows that it is a quantity per mole.In contrast, molarity is expressed per litre of solution: unit $\mathrm{mol\,L}^{-1}$.Molality is expressed per kilogram of solvent: unit $\mathrm{mol\,kg}^{-1}$.Mass concentration is expressed per litre of solution: unit $\mathrm{g\,L}^{-1}$.Therefore, molar mass is the only option that represents a quantity per mole.Answer:B. Molar mass