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Difficulty: MediumSimple and Fractional Distillation

A miscible liquid mixture contains three organic compounds: Liquid X (boiling point 78.3∘C78.3^\circ\text{C}), Liquid Y (boiling point 97.1∘C97.1^\circ\text{C}), and Liquid Z (boiling point 117.7∘C117.7^\circ\text{C}). If this mixture is subjected to fractional distillation using an efficient fractionating column, which component will be collected first as the distillate?

  1. Liquid X, because it has the lowest boiling point and the highest volatility among the components.Answer
  2. B
    Liquid Z, because components with higher boiling points vaporize more rapidly and distill over first.
  3. C
    Liquid Z, because the component with the highest boiling point reaches the top of the fractionating column first.
  4. D
    Liquid Y, because the liquid with an intermediate boiling point distills first before the extreme components.

Answer

Liquid X will be collected first as the distillate because it has the lowest boiling point (78.3∘C78.3^\circ\text{C}) and highest volatility.
In fractional distillation of miscible liquids, components separate based on differences in their boiling points. Liquid X has the lowest boiling point (78.3∘C78.3^\circ\text{C}) among the three components, meaning it is the most volatile. As heat is applied, Liquid X vaporizes most readily and its vapors ascend to the top of the fractionating column first, where they enter the condenser and are collected as the first distillate fraction.

Step-by-Step Solution

1
Compare the boiling points of the three miscible liquids in the mixture.
Liquid X has a boiling point of 78.3∘C78.3^\circ\text{C}, Liquid Y has 97.1∘C97.1^\circ\text{C}, and Liquid Z has 117.7∘C117.7^\circ\text{C}.
The boiling point determines the relative volatility of each liquid component.
2
Relate boiling point to volatility and order of vaporisation during fractional distillation.
Liquid X, having the lowest boiling point, has the highest vapor pressure at any given temperature and evaporates most readily.
Lower boiling point corresponds to weaker intermolecular forces and higher volatility.
3
Determine which component emerges first from the top of the fractionating column.
Vapors of Liquid X reach the top of the fractionating column first, condense in the Liebig condenser, and are collected as the first fraction (distillate).
Repeated condensation-vaporization cycles in the column enrich the rising vapor with the most volatile component.

Key Concept

Fractional Distillation and Boiling Point Volatility Order
Estimated Time:1m 0s
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Topics

Simple and Fractional Distillation

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