Techniques in preparation and purification

Question 1

What does refluxing allow us to do?

Answer 1

Heat a mixturs for a long period of time without any reactants or products evaporating

Question 2

What is put in round bottom flask when refluxing?

Answer 2

Anti bumping granules

Question 3

Reflux set up

Answer 3

Condenser is placed on top of round bottom flask with water in at bottom and out the top.

Question 4

Why do we recrystallise?

Answer 4

To purify an impure solid.

Question 5

Recrystallisation process

Answer 5

Dissolve impure solid in a small volume of suitable heated solvent. If not all dissolve add small volumes of solvent until solid is fully dissolved. Any insoluble impurities are removed via vacuum filtration. Filtrate is cooled down, product will crystallise and impurities will remain dissolved. It is vacuum filtered again to leave pure crystals.

Question 6

What makes solvent suitable for recrystallisation?

Answer 6

Desired product is readily soluble in solvent at high temperatures but insoluble at lower temperatures.

Question 7

Why is filter paper and funnel heated before use?

Answer 7

To porevent the solute prematurely crystallising on its cold surface reducing yield.

Question 8

Vacuum filtration?

Answer 8

Filtration carried out under reduced pressure so occurs faster than gravity filtration.

Question 9

Distillation

Answer 9

Heat liquid or mixture until either product evaporates off or impurities that are more volatile.

Question 10

Solvent Extraction equipment

Answer 10

Separating funnel

Question 11

Solvent extraction solvent:

Answer 11

Product should be more soluble in it than original mixture and should form an immiscible layer with other solution