Question

Which of the following statements are correct ?
A. Glycerol is purified by vacuum distillation because it decomposes at its normal boiling point
B. Aniline can be purified by steam distillation as aniline is miscible in water.
C. Ethanol can be separated from ethanol water mixture by azeotropic distillation because it forms azeotrope.
D. An organic compound is pure, if mixed M.P. is remained same.
Choose the most appropriate answer from the options given below :

• A. A, B, C only
• B. A, C, D only
• C. B, C, D only
• D. A, B, D only

Answer 1

The Correct Option is B

To determine which statements are correct, let's evaluate each one based on chemical principles:

1. Statement A: Glycerol is purified by vacuum distillation because it decomposes at its normal boiling point.
   • Glycerol does indeed decompose at its normal boiling point (290 °C), making vacuum distillation an appropriate method to purify it by lowering the boiling point to prevent decomposition. This statement is correct.
2. Statement B: Aniline can be purified by steam distillation as aniline is miscible in water.
   • Aniline is not completely miscible in water. However, aniline can still be purified by steam distillation because it is volatile enough to be distilled with steam. As the statement claims miscibility in water, it is misleading. So this statement is incorrect.
3. Statement C: Ethanol can be separated from ethanol-water mixture by azeotropic distillation because it forms azeotrope.
   • Ethanol and water do indeed form an azeotrope and can be separated by azeotropic distillation. Therefore, this statement is correct.
4. Statement D: An organic compound is pure if the mixed melting point remains the same.
   • A pure organic compound will show a sharp melting point. If the mixed melting point with another substance remains the same as the pure compound, this indicates purity. Thus, this statement is correct.

After evaluating each statement, the correct answer is: A, C, D only.

Answer 2

• A: True. Glycerol decomposes at its normal boiling point, so it is purified by vacuum distillation.
• B: False. Aniline is immiscible in water but can still be purified by steam distillation.
• C: True. Ethanol forms an azeotrope with water, making azeotropic distillation effective for separation.
• D: True. A pure organic compound exhibits the same melting point even when mixed with another sample of the same compound.