Matching separation techniques to mixture types

Steps:

• Identify mixture types: solutions (dissolved solids/liquids), gases, or insolubles in solids.
• Recall techniques: chromatography for colored/dissolved components, evaporation for soluble solids from liquids, fractional distillation for similar boiling liquids/gases, filtration for insolubles.
• Evaluate each option against the correct method for the substances.
• Select the option where the technique matches the mixture properties.

Why C is correct:

• Fractional distillation separates gases like oxygen and nitrogen based on slight boiling point differences (oxygen at -183°C, nitrogen at -196°C), allowing sequential condensation.

Why the others are wrong:

• A: Chromatography separates dyes or complex mixtures, not dissolving/reforming copper(II) sulfate from water (use crystallization instead).
• B: Evaporation removes solvent but cannot separate similar liquids like methanol (b.p. 65°C) and ethanol (b.p. 78°C); fractional distillation is needed.
• D: Filtration separates insolubles like sand from soluble barium sulfate, but both are solids; use acid dissolution or density differences instead.

Final answer: C