In which mixture can distillation be useful?

Correct answer: Obtaining water from salt solution

Direct answer: Option A, obtaining water from a salt solution. Distillation separates substances by differences in boiling points and includes vaporisation followed by condensation. Step by step: heat the salt solution; water, the volatile component, changes into vapour; dissolved salt does not vaporise under these conditions; cool the vapour; it condenses as liquid water in another container. A is correct because it recovers the solvent, water, and leaves salt behind. B, rice and pebbles, can be separated by handpicking or sieving because the solid pieces differ in size and appearance. C, iron filings and sand, are better separated with a magnet because iron is magnetic. D, cloth and paper, can be separated by hand or by suitable physical sorting, not normally by distillation. Distillation is especially useful when a liquid must be recovered from a solution. Memory cue: distillation means boil, carry vapour, cool and collect.