Chapter 29 - Chromatography And Spectroscopy

Question 1

Chromatography def

Answer 1

Small scale separation of components within a mixture

Question 2

Chromatography uses

Answer 2

Sksksksk

Question 3

Solvent def

Answer 3

Liquid which solute dissolves in

Question 4

Solute def

Answer 4

Substance which is dissolved in the solvent to make a solution

Question 5

Adsorption def

Answer 5

Process by which particles adhere to the surface of a solid

Question 6

Partition def

Answer 6

when a solute is distributed between two phases in a separation process
- distribution of solid particles (in solute) between two solvents

Question 7

Mobile phase def

Answer 7

The phase which moves through the stationary phase

- the solvent used (liquid or gas)

Question 8

Stationary phase def

Answer 8

The phase that doesn’t move

- may be a solid (TLC) or a liquid (GC) held by a …

Question 9

Thin Layer Chromatography (TLC) info

Answer 9

Mobile phase: Liquid - organic solvent

Stationary phase: Solid - aluminium oxide or silicon oxide coated plastic

Question 10

How to reveal spots on TLC that aren’t visible

Answer 10

• Iodine crystal
• Ninhydrin
• Impregnate TLC with fluorescent chemical - so substance glows under UV light

Question 11

Thin Layer Chromatography method (6 Marker potentially)

Answer 11

1. Place sample using micropippete on TLC plate (on baseline)
2. Add around 1cm3 solvent in beaker
3. Add TLC plate to the solvent
4. Add lid to prevent solvent from evaporating
5. Leave for mobile phase to reach almost the top
6. Take out the TLC and leave to dry - mark where solvent has moved to
7. View results - using ninhydrin, iodine crystals UV light for fluorescent etc.
8. Record Rf value by measuring pigment spots from the middle!

Question 12

Gas chromatography info

Answer 12

Mobile phase: gas, e.g. N2 or Argon - known as the carrier gas
Stationary phase: liquid or solid (with a support)
Separation occurs via etc. on slides

Question 13

Dododo

Answer 13

Data is recorded by retention times
This is time of injection of sample and emergence of a component from under the column
Area under the graph gives an indication of the amount of each component present

Question 14

Limitations of gas chromatography

Answer 14

Similar compounds have similar retention times
Hard to identify unknown compounds as reference times depend on flow rate of carrier gas and the temperature of the column

Question 15

Uses of GC-MS

Answer 15

• Analysis in forensics
• environmental analysis
• airport security
• space probes

Question 16

State why argon and nitrogen are suitable carrier gases for gas chromatography.
(1 Mark)

Answer 16

They are very inert - don’t react with mixture components

Question 17

Give two reasons why different amino acids have different Rf values.
(2 Marks)

Answer 17

• They have different solubilities in the stationary phase

- They have different solubilities in the mobile pgase

Question 18

Which reagent is used to locate the amino acid spots?

Answer 18

Ninhydrin