Chemistry: Distillation Process

Questions and Answers

The rate of evaporation is independent of the temperature.

The rate of evaporation is directly proportional to the temperature. (correct)

The rate of evaporation decreases as the temperature increases.

The rate of evaporation is inversely proportional to the temperature.

Evaporation is a faster process, while boiling is slower.

Evaporation is only possible at high temperatures, while boiling can occur at low temperatures.

Evaporation occurs at the boiling point of a liquid, while boiling occurs below it.

Evaporation occurs on the surface of a liquid, while boiling occurs throughout the liquid. (correct)

Vacuum distillation

Fractional distillation

Simple distillation

Steam distillation (correct)

To cool the vapor Signup and view all the answers

Simple distillation is used for pure substances, while fractional distillation is used for mixtures. Signup and view all the answers

To prevent decomposition of the substances Signup and view all the answers

It increases the rate of evaporation Signup and view all the answers

High vapour pressure decreases the rate of evaporation Signup and view all the answers

To prevent the formation of a scum or a layer at the upper layers of the liquid Signup and view all the answers

The rate of evaporation is inversely proportional to the atmospheric pressure Signup and view all the answers

Study Notes

Definition: Distillation is the process of vaporizing a liquid, re-condensing it, and collecting it in a container.
Boiling point of mixtures depends on mole fraction of the component present.
In pure substances, temperature remains constant during distillation as long as both vapor and liquid are present.
In miscible liquid mixtures, temperature increases throughout the process because the composition of vapor changes continuously.

Evaporation is a type of vaporization that occurs only on the surface of a liquid.
Theoretically, evaporation means the free escape of vapors from the surface of a liquid below its boiling point.

Temperature: rate of evaporation is directly proportional to temperature.
Surface area: rate of evaporation is directly proportional to the surface area of the content vessel exposed.
Agitation: stirring or agitating the solution prevents decomposition of the preparation at the bottom of the container.
Atmospheric aqueous vapour pressure: rate of evaporation is affected by atmospheric moisture content.
Atmospheric pressure on the liquid under evaporation: rate of evaporation is inversely proportional to atmospheric pressure on the surface of the liquid.

Maximum evaporation is attained at the boiling point of the liquid.
Thermostable preparations can be evaporated at higher temperatures, while thermolabile preparations require low temperatures.
Extremely heat-sensitive substances are evaporated under reduced pressure.
Time required for evaporation is critical, and evaporation should be carried out for a short time at low temperature.