Question

An organic liquid vaporizes at a temperature _________ its boiling point in steam distillation.

• A. above
• B. below
• C. equal to
• D. none of the above

Answer 1

Answer: (B)

below

In steam distillation, the mixture boils when the sum of vapour pressures of water and the organic liquid becomes equal to the atmospheric pressure. Since the vapour pressure of water is appreciably higher than that of the organic liquid, it vaporizes at a temperature much lower than its normal boiling point.

In this way, many organic compounds insoluble in water can be purified at a temperature well below the point at which decomposition occurs.