Question

Describe the side effect of rotavapping that makes it necessary to place a warm water bath underneath. Name the reason for this side effect, using thermochemistry.

Answer 1

Roto-evaporator works on the priciple of decrease in boiling point with decrease in external pressure.

In roto-evaporator, we use exterrnal vacuum pump to decrease the pressure inside the round-bottom flask, so boiling point of the solvent decreases with decreases in pressure.

Rotation of round-bottom flask is done to increase surface area of liquid.

This process is also called, evaporation under reduced pressure.

The condensing of vapour pushes the equilibrium to vapour phase according to Lechatlier's principle.