Question

What is the effect of the following on the separation of the mixture(hexane and toluene)?
a. A soluble, nonvolatile impurity
b. a decrease in barometric pressure
c. an increase in barometric pressure
d. rapid heating rate

Answer 1

I take we are talking about fractional distillation.

a. In terms of the separation a small amount of a soluble nonvolatile impurity will have no effect. There will be a small increase in each of the boiling points, which are already well separated.

b. A decrease in the barometric pressure will bring the boiling points closer together and thus more theoretical plates are needed to achieve separation. Or, if you like with the same apparatus, a poorer separation.

c. An increase in barometric pressure will increase the separation of the boiling points, so less theoretical plates needed. Or, if you like with the same apparatus, a better separation.

d. Not quite sure what is meant by this. Is the implication that the vapour is not at equilibrium?