JAMB Chemistry 2020 Paper

Concept:Fractional distillation separates the components of a mixture by their different boiling points.Explanation:Liquid air is a mixture of gases such as nitrogen ($\mathrm{N}_2$) and oxygen ($\mathrm{O}_2$) with different boiling points.When liquid air is heated slowly, the component with the lower boiling point evaporates first and is collected separately.This makes nitrogen from liquid air a direct product of fractional distillation.Sodium chloride ($\mathrm{NaCl}$) from sea water is better obtained by evaporation or crystallisation.Iodine from a solution in carbon tetrachloride and sulphur from carbon disulphide are recovered by evaporating the solvent, not by fractional distillation.Answer:A. Nitrogen from liquid air.