A liquid mixture of ethyl alcohol (ethanol) and water forms a pair of completely miscible liquids with different boiling points. Which separation method is best suited to separate this mixture into its components?

Introduction / Context:
This question deals with separation techniques for liquid mixtures. Ethyl alcohol (ethanol) and water are completely miscible liquids. The question asks which method is suitable for separating such a mixture, highlighting the importance of differences in boiling points and the use of distillation techniques in chemistry and industry.

Given Data / Assumptions:

• The mixture consists of ethyl alcohol and water.
• These two liquids are miscible in all proportions at ordinary temperatures.
• They have different boiling points (ethanol lower, water higher).
• We must choose among methods such as evaporation, sublimation, separating funnel, fractional distillation and chromatography.

Concept / Approach:
When two liquids are completely miscible but have different boiling points, the standard method of separation is fractional distillation. This technique uses a fractionating column, which allows repeated condensation and vaporisation cycles, enriching the more volatile component (ethanol) in the distillate. Simple evaporation would remove both components eventually, and a separating funnel cannot separate miscible liquids. Sublimation is only suitable when one component is a sublimable solid. Therefore, fractional distillation is the correct method.

Step-by-Step Solution:
1) Recognise that ethanol and water form a homogeneous liquid mixture because they are mutually soluble in all proportions.2) Check the boiling points: ethanol boils at a lower temperature than water under standard pressure.3) Separation of miscible liquids with different boiling points is best achieved by fractional distillation, not by separating funnels or simple evaporation.4) In fractional distillation, the mixture is heated and vapour rises through a fractionating column, where repeated condensation and vaporisation enriches the vapour in the more volatile component.5) The vapour reaches the condenser, cools and is collected as distillate that is richer in ethanol, while water remains longer in the boiling flask.6) This process eventually allows collection of fractions with differing compositions and can approach pure ethanol and pure water with proper control.

Verification / Alternative check:
Laboratory manuals describe the fractional distillation of ethanol water mixtures as a classic experiment. Industrially, large distillation columns are used to concentrate ethanol from fermentation broths. In these examples, a fractionating column is essential for efficient separation due to repeated equilibration between liquid and vapour phases. Methods like using a separating funnel are explicitly stated to work only for immiscible liquid mixtures, such as oil and water, not for miscible pairs like ethanol and water.

Why Other Options Are Wrong:
Simple evaporation to dryness: This would remove ethanol first but would also eventually remove water, and it does not allow separate collection of both components as pure liquids.
Sublimation of one component: Neither ethanol nor water is a subliming solid under ordinary conditions; both are liquids at room temperature.
Using a separating funnel: A separating funnel relies on immiscible liquids forming layers; ethanol and water are completely miscible and form only one layer.
Simple paper chromatography: Chromatography is useful for separating components in solution on a stationary phase, not for bulk separation of two miscible solvents.

Common Pitfalls:
Students sometimes think of separating funnels for any liquid mixture, forgetting the important condition of immiscibility. Another confusion is with simple distillation, which can separate some mixtures but is less efficient when boiling points are close. Fractional distillation with a column is the standard answer in exams for separating mixtures like ethanol and water. Remember that when you see miscible liquids with different boiling points, fractional distillation is usually the correct technique.

Final Answer:
A mixture of ethyl alcohol and water is best separated by fractional distillation of the liquid mixture.