Organic Techniques

Question 1

Give advantages and a disadvantage of using simple distillation rather than fractional distillation

Answer 1

Advantages:

• quicker
• easier to set up

Disadvantage:

doesn’t separate liquids as well as fractional distillation

Question 2

When should simple distillation be used?

Answer 2

If the boiling temperature of the liquid you want to purify is very different to the other liquids in the mixture (ideally a difference of 25°C or more)

Question 3

Why is a fractional column filled with glass beads/pieces of broken glass?

Answer 3

Acts as a surface on which the vapour leaving the column can condense on and then be evaporated again as more hot vapour passes up the column

Question 4

Why is a fractional column better at separating a mixture?

Answer 4

Vapour undergoes several repeated distillations as it passes up the column so separates more in the process

Question 5

When is it best to use fractional distillation?

Answer 5

When there are small differences in the boiling temperatures of the compounds in a mixture