RP10 (2) - Preparation of a Pure Organic Liquid

Question 1

Describe how to purify an organic liquid

Answer 1

Put the distillate of impure product into a separating funnel.

Wash product by adding either sodium hydrogencarbonate solution , shaking and
releasing the pressure from CO2 produced. or saturated sodium chloride solution

Allow the layers to separate in the funnel, and then run and discard the aqueous layer.

Run the organic layer into a clean, dry conical flask and add three spatula loads of drying agent (e.g. anhydrous sodium sulfate, calcium chloride) to dry the organic liquid.

When dry the organic liquid should appear clear.

Carefully decant the liquid into the distillation flask

Distil to collect pure product

Question 2

What does sodium hydrogencarbonate do

Answer 2

Neutralises remaining acid

Question 3

What does the sodium chloride do

Answer 3

Helps separate the organic layer from the aq layer

Question 4

Which layer will be on the top and why

Answer 4

The organic layer will usually be on the top. The layer with lower density will be the upper layer.

Question 5

Conditions for the drying agent

Answer 5

Insoluble in organic liquid
Should not react with the organic liquid

Question 6

What does sulfuric acid act as in preparation of ester

Answer 6

Catalyst

Question 7

How is sulfuric acid added

Answer 7

Drop by drop to prevent uncontrolled boiling over

Question 8

What is calcium chloride acting as

Answer 8

Drying agent