Ochem 341L - Lab 4

Distillation can be used

(i) to remove a nonvolatile impurity from a volatile compound (ii) to remove a volatile impurity from a nonvolatile compound (iii) to separate two or more volatile compounds, which have sufficiently different boiling points.

Distillation

is a process used to separate compounds based on differences in their boiling points.

True or False: Always distill all compounds to dryness.

False

True/False: Distillation can be used to separate two or more volatile compounds, which have the same boiling points.

False

True/False: Heptane (boiling point 98 oC) and toluene (boiling point 111 oC) can be efficiently separated by simple distillation.

False

Fractional Distillations

Fractional distillation is used when two compounds to be separated have boiling points that differ by less than 40 degrees Celsius

What volume of a round-bottomed flask is the best option to distill 35 mL of a liquid?

50 ml

Which of the following is NOT a part of a distillation apparatus? A. Buchner funnel b. condenser c. round-bottomed flask d. thermometer

A. Buchner Funnel

The formula of toluene is: a. C7H8 b. C7H14 c. C7H16 d. C6H6

A. C7H8

Which of the following compounds will be distilled during Experiment 4? a. hexane b. cyclohexane c. heptane d. cyclopentane

B. Cyclohexane

Simple Distillations

Is used when two compounds to be separated have boiling points that differ by more than 40 degrees Celsius and separated in one vaporization step.

Things to check in your apparatus

a) the correct position of the thermometer relative to the arm of the distilling head; b) the direction of water flow in the condenser (it must be opposite to the direction of the vapors); c) a few boiling chips in the round- bottom flask are necessary to ensure smooth boiling; d) the proper use of clamps e) tight connection of tubings and all glass pieces of the apparatus.

Two flammable organic compounds in experiment 4

cyclohexane and toluene

Purpose

• Learn how to perform distillation of organic compounds: - Separate two miscible liquids, cyclohexane and toluene, by simple distillation. - Estimate the efficiency of simple distillation on the basis of the experimental data.

Things to Avoid during Distillation

• Never heat a closed container. It means that a distillation apparatus must have an opening to the atmosphere. • Never place boiling chips to a heated liquid. They must be added to the liquid before distillation. • Never distill to dryness as some compounds can form non- volatile impurities, which can explode when heated. • Never use a Bunsen burner as a heat source.