Chromatography

Question 1

How to carry out chromatography?

Answer 1

1. A pencil line is drawn on chromatography paper and spots of the sample are placed on it
2. The paper is then lowered into the solvent container, making sure that the pencil line sits above the level of the solvent so the samples don’t wash into the solvent container
3. The solvent travels up the paper by capillary action, taking some of the coloured substances with it

Question 2

What is chromatography used for?

Answer 2

Used to separate mixtures and give information to help identify substances

Question 3

What does separation depend on?

Answer 3

Separation depends on the distribution of substances between the phases

Question 4

How to find the retardation factor?

Answer 4

Rf value = distance moved by substance ÷ distance moved by solvent

Question 5

How does the Rf values help to identify the compounds?

Answer 5

Different compounds have different Rf values in different solvents, which can be
used to help identify the compounds

Question 6

What are locating agents?

Answer 6

A substance used to detect another substance making it visible

Question 7

What will a pure substance produce on the paper?

Answer 7

One spot

Question 8

How to tell if 2 substances are the same?

Answer 8

They will produce the same color of spot and their spots will travel the same distance up the paper

Question 9

Why is pencil used in chromatography?

Answer 9

Pencil is used for this as ink would run into the chromatogram along with the samples

Question 10

Why do some some solvets travel further than others?

Answer 10

The components have different solubilities in a given solvent (e.g. different coloured inks that have been mixed to make black ink) and different adhesion to the supporting medium