iGCSE Chemistry 0620 Extended - 12.4 Separation and purification- Exam Style Questions Paper 2- New Syllabus
▶️ Answer/Explanation
To separate a mixture of liquids with different boiling points, you need a fractional distillation setup. This includes a round-bottom flask, a fractionating column packed with glass beads, a thermometer, a condenser with a water jacket, and a receiving flask. Diagram A correctly shows this complete apparatus arrangement.
✅ Answer: A
✅ Answer: A
▶️ Answer/Explanation
When an impurity (like glucose) is dissolved in a pure solvent (like ethanol), the melting point of the solution decreases and the boiling point increases. This is due to colligative properties. Pure ethanol melts at -114°C, so with glucose dissolved, it will melt at a lower temperature (like -116°C). Pure ethanol boils at 78°C, so with an impurity, it will boil at a higher temperature (like 79°C). Option B correctly shows both effects.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
Correct Answer: A
Explanation: The fermentation mixture contains ethanol (boiling point 78°C) and water (boiling point 100°C). Since they are miscible liquids with different boiling points, fractional distillation is used to separate them. The fractionating column allows the more volatile ethanol to vaporise first, then condense and be collected separately from water. Filtering would remove solids, not separate dissolved liquids. Ethanol does not crystallise; it is a liquid. Evaporating water would leave ethanol, but this is inefficient and less pure.
✅ Distilling the mixture using a fractionating column.