Two miscible liquids, P (boiling point 78^\circ\text{C}) and Q (boiling point 100^\circ\te… — JAMB UTME

Two miscible liquids, $P$ (boiling point $78^\circ\text{C}$ ) and $Q$ (boiling point $100^\circ\text{C}$ ), are thoroughly mixed to form a uniform, single-phase solution. Which of the following observations correctly describes the thermal behavior and nature of this mixture during distillation?

A
The liquid mixture boils at a single, fixed temperature of $89^\circ\text{C}$ .
The mixture distills over a temperature range between $78^\circ\text{C}$ and $100^\circ\text{C}$ .Answer
C
Liquid $Q$ with the higher boiling point distills over first before liquid $P$ .
D
The components can only be separated back into $P$ and $Q$ through chemical decomposition.

Answer

The mixture distills over a temperature range between

78^\circ\text{C}

and

100^\circ\text{C}

A mixture of miscible liquids retains the distinct physical properties of its constituents and lacks a fixed chemical composition. Consequently, it vaporizes and distills over a temperature range starting from the boiling point of the more volatile liquid (

78^\circ\text{C}

) up to that of the less volatile liquid (

100^\circ\text{C}

Step-by-Step Solution

Identify the type of matter described in the scenario

A uniform blend of two miscible liquids without chemical reaction forms a liquid-liquid homogeneous mixture.

No chemical bonds are formed or broken when mixing two miscible liquids.

Recall the fundamental distinctions in physical properties between pure compounds and mixtures

Pure compounds have sharp, fixed boiling points, while mixtures boil over a range of temperatures.

The vapor pressure and composition of a liquid mixture change continuously as the lower boiling component boils off.

Determine the expected distillation order and boiling behavior

Liquid

P

(lower boiling point of

78^\circ\text{C}

) vaporizes faster and distills first, causing distillation to occur over the temperature interval

78^\circ\text{C}

100^\circ\text{C}

Fractional distillation separates components based on differences in volatility and boiling point.

Key Concept

Distinction Between Compounds and Mixtures Based on Physical Constants

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

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