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JEE Advanced levelSingle correct optionDifficulty 3 of 3si105

Ethanol and water form a minimum-boiling azeotrope containing 95.6% ethanol by mass. A mixture containing 50% ethanol by mass is subjected to efficient fractional distillation. The distillate and the residue obtained are

  1. Aazeotrope (95.6% ethanol) as distillate and pure water as residue
  2. Bpure ethanol as distillate and water as residue
  3. Cpure water as distillate and pure ethanol as residue
  4. Dazeotrope as distillate and pure ethanol as residue

Answer: A

The azeotrope has the lowest boiling point, so it distils first. The feed has less ethanol than the azeotrope, so water is in excess over the azeotropic composition and remains as residue. Pure ethanol cannot be obtained by fractional distillation alone.
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