Separation Techniques

IGCSE Edexcel Chemistry
1.10-1.12 Separation methods and chromatography
Key Concept: Different mixtures are separated using differences in boiling point, solubility and particle size.

Section A: Choosing Methods

1. Name a suitable method to separate each mixture. [4]

a) Sand from water

b) Salt from salt solution

c) Ethanol and water

d) Dyes in ink

2. Explain the difference between simple and fractional distillation. [2]

Section B: Chromatography

3. Define the term Rf value. [2]
4. A dye travels 4.0 cm and the solvent front travels 8.0 cm. Calculate the Rf value. [2]

Total marks: 10

Mark Scheme

1. a) Filtration b) Crystallisation/evaporation c) Fractional distillation d) Paper chromatography [4]
2. Simple distillation separates a liquid from a solution; fractional distillation separates liquids with close boiling points using a fractionating column [2]
3. Rf = distance moved by solute / distance moved by solvent front [2]
4. Rf = 4.0 / 8.0 = 0.50 [2]