Question 1

Which of the following best describes the principle of distillation?

Accepted Answer

Distillation is the separation of the constituents of a mixture by partial vaporization and separate collection of the vapor.

Question 2

Which real-world application is most commonly associated with fractional distillation?

Accepted Answer

Separation of crude oil into gasoline and heating oil.

Question 3

At any temperature, some molecules of a liquid possess enough kinetic energy to escape into the vapor phase. What is the term for this process?

Accepted Answer

Evaporation

Question 4

Which equation best represents the relationship between vapor pressure and temperature for a liquid?

Accepted Answer

$$\ln P = -\frac{\Delta H_{vap}}{R} \cdot \frac{1}{T} + C$$

Question 5

In a simple distillation set-up, which component is most likely to be found in the distillate collected at the end?

Accepted Answer

The lower-boiling component of the mixture

Question 6

Which of the following statements correctly distinguishes fractional distillation from simple distillation?

Accepted Answer

Fractional distillation uses a fractionating column to allow multiple vaporization-condensation cycles, increasing purity.

Question 7

What is the main function of packing in a packed fractionating column?

Accepted Answer

To enhance liquid-vapor contact and improve separation efficiency

Question 8

During steam distillation, why does the mixture boil below the normal boiling point of either component?

Accepted Answer

Because the total vapor pressure is the sum of the vapor pressures of both components, allowing boiling at a lower temperature.

Question 9

Which type of distillation is most suitable for separating thermally sensitive substances?

Accepted Answer

Short path distillation

Question 10

Vacuum distillation is particularly useful for substances that:

Accepted Answer

Decompose at their normal boiling points

Question 11

Which of the following is a critical point of consideration during distillation to ensure accurate boiling point measurement?

Accepted Answer

The thermometer bulb must be even with the bottom of the side arm on the distilling head.

Question 12

If the distilling column is packed too tightly, what is the likely consequence?

Accepted Answer

Flooding of the column, hampering distillation

Question 13

Which process is used to purify solvents and liquid reaction products in an organic chemistry laboratory?

Accepted Answer

Distillation (general)

Question 14

In molecular distillation, what is the main factor that allows non-volatile substances to be separated?

Accepted Answer

Increasing the temperature and decreasing the pressure to increase the mean free path

Question 15

Which of the following best explains why the efficiency of a fractionating column depends on its length and composition?

Accepted Answer

Longer columns and appropriate packing allow more vaporization-condensation cycles, increasing purity.

Question 16

A mixture of two miscible liquids with boiling points of 78°C and 100°C is to be separated. Which distillation method is most appropriate?

Accepted Answer

Fractional distillation

Question 17

Which of the following is NOT a typical application of distillation?

Accepted Answer

Separation of non-volatile solids from volatile solids

Question 18

During distillation, if the process is too rapid due to excessive heating, what is the most likely outcome?

Accepted Answer

Poor separation due to incomplete vaporization-condensation cycles

Question 19

Which statement about the distillate collected in steam distillation is correct?

Accepted Answer

It contains both water vapor and the extracted substance in the same proportions as in the vapor phase.

Question 20

A student notices that liquid boils in the flask but none is collected in the vial during distillation. What is the most likely cause?

Accepted Answer

There is a leaking connector causing a bad connection.

Distillation: Principles, Types, and Applications in Pharmaceutical Technology

Study Guide - Practice Questions