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Equilibria between different phases

Equilibria between different phases. Advanced Higher Unit 2b(ii). Separating Funnel. Separates immiscible liquids with different densities Usually water, plus an organic solvent (ether, chloroform). [solute](organic). K =. [solute](aq). Partition Coefficient.

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Equilibria between different phases

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  1. Equilibria between different phases Advanced Higher Unit 2b(ii)

  2. Separating Funnel • Separates immiscible liquids with different densities • Usually water, plus an organic solvent (ether, chloroform)

  3. [solute](organic) K = [solute](aq) Partition Coefficient • When a solute is added to two such immiscible liquids, some will dissolve in each layer • The distribution will not be even • Ratio of distributed called PARTITION COEFFICIENT

  4. Solvent extraction • Partition coefficient is used in solvent extraction and for purification • For example, with an impure carboxylic acid, the acid will dissolve in ether but impurities will not

  5. Calculation Consider the following partition coefficient of an organic acid: [acid](ether) K = = 5 [acid](aq) If 10g of acid is dissolved in 100ml of water and 100ml ether, the quantity of acid which can be extracted can be calculated...

  6. x / 100 = 5 (10 – x) / 100 x = 5 (10 – x) x = 50 – 5x 6x = 50 x = 8.3 g [acid](ether) K = = 5 [acid](aq) Concentration organic acid (ether) = x / 100 Concentration organic acid (aq) = (10 – x) / 100

  7. An alternative method • Repeat the previous calculation, but this time for using 100 ml water and 50 ml ether for a first extraction, then repeating with another 50 ml ether for a second extraction

  8. [acid](ether) K = = 5 [acid](aq) x / 50 = 5 (10 – x) / 100 Concentration organic acid (ether) = x / 50 Concentration organic acid (aq) = (10 – x) / 100 x = 5 (10 – x) / 100 50 x = 50 – 5x / 100 50 100x = 50 – 5x 50 2x = 50 – 5x 7x = 50 x = 7.14 g

  9. [acid](ether) K = = 5 [acid](aq) x / 50 = 5 (2.86 – x) / 100 Concentration organic acid (ether) = x / 50 Concentration organic acid (aq) = (2.86 – x) / 100 x = 5 (2.86 – x) / 100 50 x = 14.3 – 5x / 100 50 100x = 14.3 – 5x 50 2x = 14.3 – 5x Total extracted: 7.14 + 2.04 = 9.18g 7x = 14.3 x = 2.04 g

  10. Chromatography • Method of separation which depends on the partition of substances between two phases • One is mobile, the other is stationary • Stationary phase – depends on type of chromatography • Paper • Thin layer • Column • Gas/liquid • High performance liquid

  11. Task • Each group take one of the chromatography types and prepare a one page notes sheet for the class and for the Think-chemistry website

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