Question

1. Briefly expalin why you should not add boiling chips to a boiling liquid?

2. Briefly explain how and why you should position the thermometer in the distillation head during a distillation

b) What is the purpose of the outer jacket on a fractionating column?

c) How is the rate of heating adjusted when using a sand bath as a heat source?

d) How is the distillate collected in a test tube microscale distillation?

3) What effect does an increase in the heatung rate have on the boiling temperature during a distillation?

Answer 1

1. Adding cold boiling chips to a boiling liquid would make a large amount of liquid to boil instantly, making the liquid to explode.

2. The thermometer in the distillation head must be above the liquid layer at a sufficient distance from the bottom. Thermomemter like this would be only in contact with vapor.

3. The outer jacket on a fractionating column helps keep the temperature constant over a range for longer period of time. It works as a heating jacket and lowers loss of heat from inner system.

4. Sand bath allows for a uniform heating system. The heating rate of sand is much better and thus heat supplied almost equals to the heat used.

5. For a test tube collection in a microscale distillation unit, a bent tip pasteur pipet is used.

6. Increase in the heating rate would cause a lot of liquid to boil at the same time, thereby allowing for low separation efficiency for the process. The boiling point would not be reliable in this case as too much heat is supplied together and no equilibrium between vapor and liquid is obtained.