Fractional Distillation

toluene

toluene

p-xylene

p-xylene

cyclohexane

cyclohexane

hickman still head

hickman still head

claisen adapter

claisen adapter

conical vial

conical vial

Why is it important that you do not add boiling chips to a boiling liquid?

a boiling chip can cause the hot liquid to foam up and burn you.

Why should the thermometer be positioned in the neck of the Hickman still head with the bulb slightly below the top of the neck?

to ensure that the vapor temperature is measured accurately.

Unlike the simple distillation column, the fractional distillation column is wrapped in aluminum foil and cotton batting. What is the purpose of the aluminum foil? (1)

What is the purpose of the cotton batting? (2)

(1) increase heat transfer

(2) insulate the apparatus

What effect does a rise in the heating rate have on the boiling temperature during distillation? If the heating rate is (1) _____ , the temperature of the boiling liquid (2) _____ , but the rate at which vapor is produced from the liquid (3) _____.

(1) increased

(2) does not change

(3) increases

As molecules move up a fractional distillation column, they condense and then revaporize. During which of these steps is the concentration of the more volatile compound of the mixture increased?

the vaporization phase

Using the figure below, estimate the percent composition of a cyclohexane : toluene distillate that is connected

at 85 degrees Celsius (1)

at 95 degrees Celsius (2)

at 105 degrees Celsius (3)

(1) 75:25

(2) 40:60

(3) 15:85

What effect does a rise in the heating rate have on the boiling temperature during distillation? If the heating rate is (1) _____ , the temperature of the boiling liquid (2) _____ , but the rate at which vapor is produced from the liquid (3) _____.