Question

Why is benzene separated from water using a separatory funnel?

Answer 1

Miscibility & Density difference

Explanation:

Benzene and water are partially miscible solvents.If we mix alcohol and water they mix together and form a homogeneous mixture. Separating such mixtures require more energy. Hence we use distillation.

But Benzene and water form a non homogeneous mixture, with very little mixing in the interface.We can just let the mixture stand still for long time. They will separate into 2 layers because of the difference in densities. Top layer will be benzene and the bottom layer will be water. Hence we can separate them using a separating funnel.

Answer 2

You are correct, benzene COULD be separated from water by distillation........

Explanation:

But it would be inconvenient, and very tedious to do so........the normal boiling points of water and benzene (`80.1` `""^@C`) are not all that different, and when you heated them up, I suspect that you would form an azeotrope. And if there were two phases, distillation would cause a lot of bumping in the distillation flask.

It would be far more convenient to use a sep funnel, and dry the benzene layer after separation. And this is the standard procedure in many organic reactions: (i) do the reaction; (ii) quench the reaction with water; (iii) extract the product with ether or toluene; (iv) dry the organic extract; (v) remove the solvent; (vi) recrystallize or distill the product.

It is also a fact that chemists try to limit their exposure to benzene. All these manipulations would be performed in a well-ventilated hood.