The Question is from neet-chemistry organic-chemistry-basics qualitative-and-quantitative-analysis, and it was created by the author P SRAVAN KUMAR

Question

A mixture of two volatile liquids A and B is distilled. The boiling point of A is 70°C and that of B is 90°C.  Assuming ideal behavior, which of the following statements is true regarding the initial distillate?

P SRAVAN KUMAR · Accepted Answer

## CORE INFORMATION
✓ **Answer**: A
## CONCEPT FRAMEWORK
 **Primary Concept**: Fractional Distillation
 **Related Topics**: Vapor Pressure, Raoult's Law, Boiling Point
 **Prerequisites**: Understanding of distillation and vapor pressure.
## SOLUTION PATHWAY
**Given Information**:
  * Liquid A boiling point: 70°C
  * Liquid B boiling point: 90°C
  * Ideal behavior assumed
**Method & Steps**:
 1. Understand the principle of fractional distillation.
  Reasoning: Fractional distillation separates liquids based on their boiling points. The component with the lower boiling point will vaporize first and thus be collected in the initial distillate.
  Formula/Rule:  Raoult's Law (for ideal solutions): $P_A = x_A P_A^*$, where $P_A$ is the partial pressure of A, $x_A$ is the mole fraction of A in the liquid, and $P_A^*$ is the vapor pressure of pure A.
 2. Analyze the boiling points of A and B.
  Working: Since A has a lower boiling point (70°C) than B (90°C), it will have a higher vapor pressure at any given temperature below 90°C.  Therefore, A will vaporize more readily than B.
  Key Point:  The initial distillate is enriched in the more volatile component (lower boiling point).
 3. Determine the composition of the initial distillate.
  Result: The initial distillate will be richer in A than the original mixture.
  Verification: This aligns with the principle of fractional distillation, where the lower boiling point component is preferentially collected in the early stages of distillation.
 ## OPTION ANALYSIS
A ✓: The distillate will be richer in A than the original mixture. (Correct. A has a lower boiling point and will vaporize more readily.)
B :x: The distillate will be richer in B than the original mixture. (Incorrect. B has a higher boiling point and will vaporize less readily.)
C :x: The distillate will have the same composition as the original mixture. (Incorrect. Distillation separates components based on boiling points.)
D :x: The distillate will contain only A. (Incorrect.  While A is preferentially collected, some B will also be present in the initial distillate.)
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing boiling point with vapor pressure:  Lower boiling point means higher vapor pressure at a given temperature.
  2.Assuming complete separation in the initial distillate: The initial distillate is enriched in the lower boiling point component, but not exclusively composed of it.
 **Quick Tips**:
  1.Remember that the lower the boiling point, the higher the vapor pressure, and therefore the more volatile the substance.
  2.Visualize the distillation process: Imagine the liquid with the lower boiling point evaporating first and condensing in the receiving flask.

P SRAVAN KUMAR · Answer

The correct Option is "The distillate will be richer in A than the original mixture."

P SRAVAN KUMAR · Answer

The distillate will be richer in B than the original mixture.

P SRAVAN KUMAR · Answer

The distillate will have the same composition as the original mixture.

P SRAVAN KUMAR · Answer

The distillate will contain only A.

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