A homogeneous mixture contains two liquids. How are they separated ?
- A.By filtration
- B.By evaporation
- C.By distillation
- D.By condensation
Correct answer
Explanation
The correct answer is C, By distillation. Two miscible liquids that form a homogeneous mixture are separated by distillation, which uses the difference in their boiling points.
In distillation the mixture is heated; the liquid with the lower boiling point turns to vapour first, the vapour passes through a condenser, cools back into liquid and is collected separately. Simple distillation works when the boiling points differ by more than about 25 degrees Celsius, as with acetone and water. When the boiling points are close, fractional distillation with a fractionating column is used, as in separating the gases of air or the fractions of crude oil.
A is wrong because filtration separates insoluble solids from a liquid, not two liquids that are fully mixed. B is wrong because evaporation removes a liquid to recover a dissolved solid and loses the liquid. D is wrong because condensation is only one step inside distillation, not a method of separation by itself.
Exam tip: miscible liquids need distillation; immiscible liquids such as oil and water need a separating funnel.
Practice Questions
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- C.James Watt
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