iGCSE Chemistry (0620) Core:12.4 Separation and purification: Exam Style Questions Paper 1- New Syllabus
▶️ Answer/Explanation
Detailed solution:
The apparatus shown is clearly a filtration setup: a filter funnel lined with filter paper, collecting a liquid (filtrate) in a beaker below while a solid (residue) remains on the filter paper. Filtration works by separating an insoluble solid from a liquid. Option A consists of two aqueous solutions—both are dissolved and would both pass through the filter paper, so filtration would not separate them. Option C is a mixture of two miscible liquids (ethanol and water), which requires fractional distillation, not filtration. Option D contains two insoluble solids (sand and calcium carbonate), and both would be trapped by the filter paper, giving no separation. Only option B has one insoluble solid (copper(II) hydroxide) and one aqueous solution (calcium chloride), which is exactly the type of mixture that filtration can separate.
▶️ Answer/Explanation
Detailed solution:
When excess solid magnesium oxide is added to dilute nitric acid, the acid reacts to form soluble magnesium nitrate and water, but the unreacted magnesium oxide remains as an insoluble solid. To remove this excess solid from the liquid, we use filtration. The mixture is poured through filter paper in a funnel; the solid remains on the filter paper (as residue) and the clear solution (filtrate) passes through.
▶️ Answer/Explanation
Detailed solution:
To separate a mixture of liquids that have different boiling points, you need a technique that exploits those boiling point differences. Fractional distillation does exactly that—it heats the mixture so the liquid with the lower boiling point vaporises first, the vapours rise up a fractionating column, and they condense and are collected separately. Simple distillation might work for two liquids with very different boiling points, but fractional distillation is the specific technique for mixtures where the boiling points could be relatively close together. Dissolving, crystallisation, and filtration are all for separating solids from liquids, not liquid-liquid mixtures.