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Difficulty: HardSimple and Fractional Distillation

Match each mixture separation scenario on the left with its corresponding distillation requirement or thermal principle on the right.

  • Separation of two miscible liquids whose boiling points differ by 15∘C15^\circ\text{C}Requires a fractionating column to provide multiple successive condensation-vaporization cycles
  • Recovery of pure water solvent from a sea water salt solutionUses simple distillation because the dissolved solute is non-volatile and exerts negligible vapor pressure
  • Industrial separation of argon (b.p. −186∘C-186^\circ\text{C}) from nitrogen (b.p. −196∘C-196^\circ\text{C})Requires cryogenic liquefied-air fractional distillation under controlled low temperatures and pressure
  • Separation of a liquid mixture where components differ in boiling point by over 70∘C70^\circ\text{C}Can be achieved via simple distillation as the vapor pressure difference ensures complete single-stage separation

Answer

The correct matches pair liquid mixtures with small boiling point differences to fractional distillation involving fractionating columns, non-volatile solute solutions to simple distillation, industrial liquefied gases to cryogenic fractional distillation, and widely separated boiling point liquids to simple distillation.
Each mixture scenario is accurately paired according to volatility differences, non-volatility of solid solutes, temperature threshold limits (25∘C25^\circ\text{C} difference rule), and specialized industrial gas liquefaction conditions.

Step-by-Step Solution

1
Analyze the thermal criteria for distillation methods based on boiling point differences.
Miscible liquids with boiling point differences less than 25∘C25^\circ\text{C} require a fractionating column (fractional distillation), whereas differences exceeding 50∘C50^\circ\text{C} allow single-stage simple distillation.
Fractionating columns create a temperature gradient allowing multiple vaporizations and condensations.
2
Evaluate the volatility of solutes in liquid solutions.
Dissolved solid salts are non-volatile and remain in the boiling flask while solvent vapor turns into pure distillate.
Non-volatile compounds do not contribute to the vapor phase pressure at distillation temperatures.
3
Examine industrial gas separation requirements.
Gaseous air components must first be liquefied cryogenically before undergoing fractional distillation to separate components with close boiling points like argon and nitrogen.
Distillation requires liquid-vapor equilibrium, which only exists for air at cryogenic temperatures.

Key Concept

Simple vs Fractional Distillation Operational Criteria
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Topics

Simple and Fractional Distillation

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