Asked in UHS MDCAT 2009 2009

The acid which can be purified by the sublimation is:

Correct answer: C. Benzoic Acid

  • A. Acetic Acid
  • B. Oxalic Acid
  • C. Benzoic Acid
  • D. Citric Acid

Explanation

Explanation:Benzoic acid has a high melting point (122°C) and a low vapor pressure, which allows it to sublime at room temperature and atmospheric pressure. Hence, the acid which can be purified by the sublimation is benzoic acid.Acetic acid has a low boiling point (118.1°C) and cannot be purified by sublimation. Oxalic acid has a decomposition temperature lower than its melting point, so it cannot be purified by sublimation. Citric acid has a decomposition temperature lower than its melting point, so it cannot be purified by sublimation.

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About Sublimation and Distillation

Sublimation separates a sublimable solid from non-sublimable impurities by direct conversion between solid and vapour, followed by deposition. Distillation separates liquids through differences in boiling points, including simple, fractional, steam and vacuum distillation, and the choice depends on volatility, miscibility and thermal stability.

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