Analytical techniques

Question 1

Infrared radiation

Answer 1

1. causes covalent bonds to vibrate
2. different bonds have different absorptions
3. frequency where they vibrate

Question 2

Greenhouse gases

Answer 2

1. absorb infrared radiation
2. high atmospheric concentration
3. long residence time
4. randomly disperses energy
5. have C=O, C-H, O-H

Question 3

CH3+ fragment

Answer 3

15

Question 4

CH3CH2+ fragment

Answer 4

29

Question 5

CH2OH+ fragment

Answer 5

31

Question 6

Molecular ion

Answer 6

1. peak with largest m/z value
2. Mr of molecule

Question 7

M+1 peak

Answer 7

1. above molecular ion
2. presence of carbon13 isotope

Question 8

Stationary phase

Answer 8

solid
liquid held by solid support

Question 9

Mobile phase

Answer 9

moves through stationary phase
liquid or gas

Question 10

Factors for chromatography separation

Answer 10

1. extent of solubility in mobile phase
2. adsorption to solid stationary phase

Question 11

Thin layer chromatopgraphy

Answer 11

1. Aluminium oxide or silicon oxide on glass plate is stationary phase
2. sample spotted onto plate
3. in shut container with solvent
4. use iodine crystal, UV or ninhydrin to make colourless compounds visible

Question 12

Rf

Answer 12

distance moved by solute/ distance moved by solvent

Question 13

Gas chromatography

Answer 13

1. sample vaporised and injected
2. carrier gas- mobile phase (nitrogen)
3. flows under pressure through column
4. stationary phase- liquid or solid on solid support
5. components separate as pass through column
6. separately detected by signal when emerge
7. retention time recorded

Question 14

Retention time

Answer 14

time between injection of the sample and the emergence of a component from the column

Question 15

Retention area

Answer 15

area = base x 1/2 x height

amount of component

Question 16

TMS standard

Answer 16

1.12H equivalent and is standardised at 0ppm
2. 4C equivalent and is standardised at 0ppm
3. volatile and easy to remove
4. chemically inert and doesn’t react
5. absorbs at very high frequency- mass spec doesn’t overlap

Question 17

TMS

Answer 17

tetramethylsilane
Si(CH3)4

Question 18

NMR method

Answer 18

1. dissolved in deuterated solvent
2. add TMS as reference
3. placed in strong magnetic field
4. range of different radio frequencies
5. different frequencies absorbed dependent on environment

Question 19

D2O

Answer 19

1. peaks for OH and NH disappear
2. peaks found too wide a range - difficult to assign

Question 20

Use of deuterated solvent

Answer 20

1. doesn’t contain protons
2. won’t produce extra peaks
3. example- CDCl3