purification of an organic solid

Question 1

exemplar use

Answer 1

purifying asprin

Question 2

steps

Answer 2

1. Dissolve the impure compound in a minimum
   volume of hot (near boiling) solvent

.2. Hot filter solution through (fluted) filter paper
quickly.

3. Cool the filtered solution by inserting beaker in ice
4. Suction filtrate with a buchner flask to separate
   out crystals

5 Wash the crystals with distilled water

6. Dry the crystals between absorbent papering

Question 3

why use the minimum volume of solvent?

Answer 3

The minimum volume is used to obtain saturated

solution and to enable crystallisation on cooling

Question 4

features of the most appropriate solvent

Answer 4

An appropriate solvent is one which will dissolve both
compound and impurities when hot and one in which
the compound itself does not dissolve well when cold.

Question 5

why Hot filter solution through (fluted) filter paper

quickly.

Answer 5

This step will remove any insoluble impurities and

heat will prevent crystals reforming during filtration

Question 6

why Cool the filtered solution by inserting beaker in ice

Answer 6

Crystals will reform but soluble impurities will remain
in solution form because they are present in small
quantities so solution is not saturated. Ice will
increase the yield of crystals

Question 7

why Suction filtrate with a buchner flask to separate

out crystals

Answer 7

The water pump connected to the Buchner flask

reduces the pressure and speeds up the filtration.

Question 8

why Wash the crystals with distilled water

Answer 8

To remove soluble impurities

Question 9

how can loss of yield occur in this process?

Answer 9

• Crystals lost when filtering or washing
• Some product stays in solution after recrystallisation
• other side reactions occurring