Kerosene and petrol mixture can be best separated by
- A.Sublimation
- B.Separating funnel
- C.Fractional distillation
- D.Compressing and cooling
Correct answer
Explanation
The correct answer is C, Fractional distillation. Kerosene and petrol mix completely with each other, and their boiling points are close, so they are separated by fractional distillation.
In fractional distillation the mixture is heated and its vapours rise through a fractionating column packed with glass beads. The liquid with the lower boiling point, petrol, reaches the top first and is condensed, while kerosene, which boils at a higher temperature, comes over later. The same method separates crude oil into petrol, kerosene, diesel and other fractions in a refinery, and separates the gases of air.
A is wrong because sublimation separates a solid that turns straight into vapour, such as camphor or naphthalene, from others. B is wrong because a separating funnel works only for liquids that do not mix, such as kerosene and water. D is wrong because compressing and cooling turns a gas into a liquid and does not separate two liquids.
Exam tip: miscible liquids with close boiling points need fractional distillation; immiscible liquids need a separating funnel.
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