Purification and Separation

Question 1

Describe extraction

Answer 1

Transfer of dissolved compound to solvent in which it’s more soluble

Question 2

What’s the desired product in gravity vs vacuum filtration?

Answer 2

Usually in gravity filtration, product in the aqueous filtrate (only impurities caught).
In vacuum, we expect a lot insoluble product.

Question 3

Mechanism of recrystallization

Answer 3

Dissolve impure solid in hot solvent (insoluble at lower temps), and let cool to recrystallize. Impurities excluded from crystal and remain in solution.

Question 4

What’s the basis of chromatography?

Answer 4

Different affinity of the solid to the stationary phase

Question 5

How to calculate R value in TLC

Answer 5

Distance compound travels / distance solvent travels

Question 6

Define flash column chromatography

Answer 6

Column chromatography sped up by forcing solvent with nitrogen gas

Question 7

Which direction to ions go in electrophoresis?

Answer 7

Cations are attracted to the cathode.

Anions are attracted to the anode.

Question 8

How to calculate electrophoresis migration velocity

Answer 8

v = Ez/f
E = E field
z = molecule net charge
f = frictional coefficient (mass and shape)

Question 9

What BP differential required for simple distillation?

Answer 9

> 25ºC

Question 10

Azeotropic mixture

Answer 10

Vapor composition same as liquid