Question

Which one of the following mixtures can be separated by steam distillation technique?

• A. n-Hexane + n-Heptane
• B. CHCl₃ + Aniline
• C. Aniline + H₂O
• D. Glucose + NaCl

Hint:

Classic examples of compounds purified by steam distillation include aniline, nitrobenzene, o-nitrophenol (to separate from p-nitrophenol), and essential oils from plants. The key characteristics to look for are immiscibility with water and steam volatility.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Steam distillation is a special type of distillation used for separating substances which are temperature-sensitive. The technique is applicable under specific conditions:
1. The organic compound to be purified must be essentially immiscible with water.
2. The compound should be volatile in steam.
3. The compound should have a relatively high vapor pressure at the boiling point of water.
4. The impurities present should be non-volatile.
Step 2: Analyzing the Options:
- (A) n-Hexane + n-Heptane: These are two miscible, non-polar hydrocarbons with different boiling points. They are ideally separated by fractional distillation, not steam distillation.
- (B) CHCl₃ + Aniline: Chloroform and aniline are miscible organic liquids. They would be separated by fractional distillation.
- (C) Aniline + H₂O: Aniline is an organic compound that is immiscible with water and is volatile with steam. Its boiling point is high (184 °C), but in the presence of steam, it boils at a temperature below 100 °C (\(\approx\) 98 °C). This mixture perfectly fits the criteria for separation by steam distillation. Aniline can be purified from non-volatile impurities using this method.
- (D) Glucose + NaCl: These are two non-volatile solids that are both soluble in water. Distillation techniques are not suitable for separating them. Methods like fractional crystallization would be used.
Step 3: Final Answer:
The mixture of Aniline and water is the one that can be separated or purified by steam distillation. Therefore, option (C) is correct.