Recrystallisation

Question 1

How do we remove impurties in crystalline solids.

Answer 1

Heat solvent and dissolve impure solid in the solvent.
The insoluble impurities sink to the bottom so use gravity filtration to keep the liquid. Let it cool and then ice bath and the crystal will form with impure solution so filter by pressure and keep crystal.

Question 2

Considerations:

Answer 2

Be careful about solvent used.
Make sure solution is hot during filtration by gravity.
Wash our crystal to remove cold solvent to remove soluble impurities

Question 3

Melring point

Answer 3

Find melting point and compare it to data book is different impurities are there

Question 4

If solid contains impurities

Answer 4

Melting piint is less then the data book as weak intermolecular forces

Question 5

Describe the method for determine the melting point of a solid?

Answer 5

Put the sample in a melting point apparatus heat it slowly and compare the melting point to the data book value

Question 6

How do you purify a liquid?

Answer 6

Solvent extraction

Question 7

How do you use solvent extraction:

Answer 7

Add liquid into separating funnel and add solvent and shake and let the mixture form a layer.
And pour out the liquid

Question 8

Consideration if solvent extraction

Answer 8

Sodium chloride cause water molecules to not mix and sodium hydorgen carbonate is used to get rid of H2SO4

Question 9

How do you get rid of water?

Answer 9

Anhydrous salt removes water drying agent