Separations

Question 1

Categories

Answer 1

Two bulk phases or bulk phase and a thin layer

Question 2

Precipitation: Crystallisation

Answer 2

Forms solid ppt. of analyte. Impurities in solution discarded. Soluble material may ppt. too (inclusion/occlusion of impurities)

Question 3

Distillation

Answer 3

Differences in volatility, requires fractional distillation and control of temperature

Question 4

Liquid-Liquid Extraction

Answer 4

Aq vs Org solvents, good for isolating solutes of low K. Solvent continuously re-circulated by re-distillation.

Question 5

Liquid-Liquid Extraction (Choice of solvent)

Answer 5

Where is analyte soluble, formation of azeotropes, densities matter, where will analyte end up to avoid discarding wrong layer, volatile solvents = increased vapour pressure

Question 6

Liquid-Liquid Extraction (Azeotropes)

Answer 6

When two layers that should separate, mix. Example: Toluene and Water

Question 7

Liquid-Liquid Extraction (Efficiency)

Answer 7

Efficiency is measured by K = [A]org/[A]aq

Question 8

Solid-Liquid Soxhlet Extraction

Answer 8

Sample placed in porous thimble in extractor. Re-distillation allows continuous delivery to extractor. Solvent slowly extracts analyte from solid matrix.

Question 9

Solid-Liquid Soxhlet Extraction (Efficiency)

Answer 9

To maintain efficient extraction, when thimble extractor filled with solvent, the solvent is siphoned back to solvent reservoir to avoid saturation of solvent