Paper 2 Pag

Question 1

Purification of an organic liquid

Answer 1

• if acid is present add sodium carbonate and let gas fizz out from separating funnel
• add a small quantity of water and allow layer to separate, run out the aqueous layer (more dense on bottom)
• add anhydrous drying agent (CaCl2) to remove
• redistill at X degrees

Question 2

Purification of aspirin/organic solid

Answer 2

• cool reaction mixture then filter under reduced pressure
• add minimum amount of hot solvent allowing to cool and recrystallise, filter under reduced pressure then leave to dry
• wash purified aspirin in cold water

Question 3

Testing purity of aspirin/organic solid

Answer 3

• place a small amount of aspirin into a melting point tube, compare it to data book value
• TLC, run chromatographs for impure and pure solid and reactants, compare rf values
• spectroscopy, nmr and compare to data

Question 4

Test for alkene

Answer 4

Bromine water, goes from orange to colourless

Question 5

Test for carboxylic acid

Answer 5

Add sodium carbonate and look for effervescence

Question 6

Test for aldehyde

Answer 6

Tollens reagent and place in water bath, silver mirror forms

Question 7

How to prepare tollens reagent

Answer 7

Test tube of silver nitrate, add drop of NaOH. Add ammonia until brown ppt dissolved and forms a colourless solution

Question 8

Test for haloalkane

Answer 8

Add silver nitrate and place in water bath, see colour of ppt, and solubility in ammonia

Question 9

Test for alcohol

Answer 9

Heat with acidified potassium dichromate, orange to green