Distillation

Distillation

Separation of compounds based on differences in their boiling points

If one compound is substantially more volatile than the other, what process is used?

Simple distillation

Volatile

high vapor pressure, low boiling point

Boiling point characteristics

Bubbles of vapor produced throughout liquid

Basis of distillation?

Change in composition that accompanies the vaporization process

When is the concentration of the more volatile compound increased during fraction distillation. Explain.

Concentration of more volatile compound increases as vapors move up column. Each condensation-revaporization phase increases concentration of more volatile compound.

Where are the pot produced vapors cooled?

Condenser

Function of fractioning column?

Contains glass beads and metal sponge. Vapor condenses on cooler surfaces, reheated by rising vapors, and re-vaporizes.

If the boiling points of two compounds differ by less than 40°C, what process is used?

Fractional distillation

Each condensation-revaporization cycle results in what?

Increase in concentration of more volatile compound.

Why does the rate of vapor produced increase in the case of which heating rate is increased during boiling?

Liquid particle absorb more energy, overcome intermolecular interactions, and enter gaseous state.

Distillation rate must not be conduced too rapidly. Why?

Liquid-vapor equilibria will not be established. Poor separation.

Fractional distillation has the effect of?

Many simple distillations

What is evaporation?

Molecules at liquid surface gain sufficient energy to enter the gaseous state

Where are compounds heated in distillation apparatus?

Pot

Equilibrium vapor pressure

Pressure exerted by gaseous particles at liquid-gas equilibrium on walls of container

Why must the fractioning column be positioned vertically?

Promote percolation

Where is the condensed liquid collected?

Receiver

Distillation is useful for what?

Removing a volatile solvent from a nonvolatile product; separate a volatile product from nonvolatile impurities; separate two or more volatile products that have sufficiently different boiling points

Mixture of two volatile compounds heated, what is the total vapor pressure?

Sum of the vapor pressures of each compound

Boiling point

Temperature at which vapor pressure is equal to external pressure exerted on liquid

When does evaporation occur?

Temperature below boiling point

Homogeneous mixture will boil at what?

Temperature between the boiling points of pure compounds

When heating rate is increased during boiling, what occurs?

Temperature does not change. Rate at which vapor is produced increases.

How and why do you position the thermometer head?

Top of thermometer should be with side arm on distilling head. Ensures head is immersed in vapor.

Distillate has the same composition as?

The vapor of which it is produced

Each condensation-revaporization is called what?

Theoretical plate

When vapor is produced from a liquid mixture, describe the vapor composition.

Vapor composition is different from that of liquid mixture. Contains a larger percent of the more volatile compound.

Define: Miscible

When two compounds form a homogeneous mixture