Chromatography

Question 1

What is chromatography used for?

Answer 1

Separating a mixture of soluble substances and identifying them

Question 2

All types of chromatography have 2 phases. What are they?

Answer 2

Mobile phase: Where the molecules can move, e.g, liquid
Stationary phase: Where the molecules can’t move, e.g, solid

Question 3

In paper chromatography, what is the stationary and mobile phase?

Answer 3

Stationary phase: Filter paper
Mobile phase: The solvent

Question 4

How fast a chemical moves through the stationary phase depends on ?

Answer 4

How it distributes itself between the two phases

Question 5

Describe the method for paper chromatography

Answer 5

1.) Draw a line 1cm from the end (the baseline) in pencil as it is insoluble in the solvent
2.) Put a spot of the mixture to be separated on the line.
3.) Put some on the solvent in the beaker and dip the bottom of the paper in the solvent, but below the spot of ink
4.) Put a watch glass on top of the beaker to stop any water evaporating, and the solvent will start to move to the paper
5.) When the chemicals in the mixture dissolve in the solvent, they will move up too
6.) Remove the paper from the beaker before it reaches the top and mark the distance the solvent has moved (Solvent front)

Question 6

How do you work the rf value of a chromatogram?

Answer 6

Distance travelled by solute ÷ distance travelled by solvent

Question 7

How do you find the distance travelled by the solute?

Answer 7

Measure from the baseline to the centre of the spot

Question 8

What will happen to a pure substance in chromatography?

Answer 8

It won’t be separated and will move as one blob

Question 9

How can you link the two phases and chromatography?

Answer 9

1.) The components in the mixture separate out as the mobile phase moves over the stationary phase
2.) They all end up on different parts of the stationary phase because they spend different amounts of time dissolved in the mobile phase and stuck to the stationary phase