Chromatography

Question 1

What category is Chromatography in?

Answer 1

Methods of separation

Question 2

What is paper chromatography used for?

Answer 2

To separate dyes - e.g. inks, paints, food colourings

Question 3

What is chromatography used for?

Answer 3

To separate out mixtures.

Question 4

How do you carry out paper chromatography?

Answer 4

1) Draw a baseline near the bottom of the paper.
2) Add different ink spots to the line at regular intervals.
3) Loosely roll the sheet and place in a beaker with a solvent.
4) Make sure the solvent level is below the baseline.
5) Place a lid on the container.
6) The solvent will rise, carrying inks with it.
7) Wait for the solvent to nearly reach the top and then take out the paper and leave to dry.

Question 5

What should the baseline be drawn with, and why?

Answer 5

Pencil as the marks are insoluble so it won’t dissolve in the solvent.

Question 6

State a liquid that is commonly used as a solvent in paper chromatography:

Answer 6

Water or Ethanol

Question 7

Why must the solvent level be below the baseline?

Answer 7

So that the inks do not dissolve into the solvent

Question 8

Why is a lid used?

Answer 8

To stop the solvent from evaporating.

Question 9

What is the end pattern on the paper called?

Answer 9

Chromatogram

Question 10

State what is commonly used as a lid.

Answer 10

Watch glass

Question 11

Why would a dye likely not move up the paper?

Answer 11

Because it is non-soluble in the current solvent.

Question 12

What should be done if a dye does not move from the pencil line?

Answer 12

Find a new solvent as this dye is non-soluble in the current one.

Question 13

What should be done if a dye moves up the paper with the solvent front?

Answer 13

Find a new solvent as this dye is too soluble in the current one.

Question 14

What is the affinity of a dye?

Answer 14

How well the dye ‘sticks’ to a paper.

Question 15

If there are 3 spots created by the dye up the paper, what can be said about the number of different dyes present in the spot?

Answer 15

There are at least different dyes, it is possible that one of the spots is made form more than one colour.

Question 16

Where is the distance moved by an ink measured from?

Answer 16

The middle of the ink spot to the base line

Question 17

What does Rf stand for?

Answer 17

Retardation Factor

Question 18

What is the Retardation Factor?

Answer 18

A ratio of distance travelled by the spot and the distance travelled by the solvent.

Question 19

What are the boundaries that an Rf vale has to be within?

Answer 19

0 and 1.

Question 20

What is the equation for Rf?

Answer 20

Distance moved by a spot (from baseline) /

Distance moved by solvent front (from baseline)

Question 21

What are the units for an Rf value?

Answer 21

Rf has no units

Question 22

Suggest why the Rf has no units?

Answer 22

It is simply a ratio.

Question 23

What are Standard Reference Materials? (SRM’s)

Answer 23

Pure substances which have controlled concentrations and purities. They are often run against a mixture to check for the identities of its components.

Question 24

Why does chromatography work?

Answer 24

Different dyes will move up the paper at different rates.

Question 25

What can be described as a solute in the experiment?

Answer 25

The dyes.