AS Practical Skills

Question 1

Why do we add anti-bumping granules to our flask in distillation and reflux?

Answer 1

To provide controled evaporation/boiling

Question 2

What can be used to heat up the flask in distillation/reflux?

Answer 2

Electric heating mantle or water bath

Question 3

Why is it beneficial to collect distillate from distillation in a test tube inside ice water?

Answer 3

Organic liquids are volatile so this prevents vaporisation

Question 4

Why is a stopper not needed in reflux?

Answer 4

The sample/product we are making will evaporate and travel up but long before it gets to the top it condenses and travels back down.

Question 5

Describe the apparatus and procedure for purification of an organic liquid containing water.

Answer 5

• Add organic product to separating funnel
• Add distilled water to allow layers to separate. The layer that gets bigger is the aqueous layer. All the water in the organic layer goes into/mixes with distilled water.
• Allow aqueous/organic layer to run out (depends which is on bottom)
• Collect organic layer in conical flask
  -just in case there is still water, add a drying agent
• Filter it or decant it (pour off liquid, leaving solid behind.
• You are left with a pure organic substabce

Question 6

Give examples of drying agents to use when separating water from an organic substance?

Answer 6

Anhydrous CaCl2 or anhydrous MgSO4. They readily absorb any traces of water left in the organic liquid

Question 7

Describe the procedure for purifying an organic liquid containing another organic liquid.

Answer 7

• Redistillation
  -Temperature is carefully controlled to make sure only desired product is distilled across.

Question 8

Why can you get mixtures of organic liquids when only making one?

Answer 8

They have similar boiling points so distill together