Chapter 29 - Chromatography and Spectroscopy

Question 1

What are the two phases for all forms of chromatography?

Answer 1

Stationary phase

Mobile phase

Question 2

What is the stationary phase?

Answer 2

Does not move

A solid or a liquid supported on a solid

Question 3

What is the mobile phase?

Answer 3

Does move

Normally a liquid or a gas

Question 4

What is a TLC plate made of?

Answer 4

Plastic/glass sheet

Coated with thin layer of a solid adsorbent substance such as silica

Question 5

Outline adsorption in reference to TLC

Answer 5

Process by which the solid silica holds the different substances in the mixture to its surface

Question 6

How is the retention factor calculated?

Answer 6

Distance moved by the component/distance moved by the solvent front

Question 7

What is gas chromatography useful for?

Answer 7

Separating and identifying volatile organic compounds present in a mixture

Question 8

What are the different phases for gas chromatography?

Answer 8

Stationary - high boiling liquid adsorbed onto an inert solid support
Mobile - inert carrier gas such as helium

Question 9

How does time taken to move through the column change as solubility in stationary phase increases?

Answer 9

Moves slower

Time taken increases

Question 10

What is retention time?

Answer 10

Time taken for a component to travel through the column

Question 11

How is retention time used for identification?

Answer 11

Compare to retention times in database

Question 12

What can peak integrations for gas chromatograph be used to determine?

Answer 12

Concentrations of components in the sample

Question 13

What is resonance for NMR?

Answer 13

When the nucleus absorbs energy and rapidly flips between the two spin states

Question 14

What is the standard reference chemical for NMR?

Answer 14

Tetramethylsilane (TMS)

(CH3)4Si

Question 15

What is the purpose of D2O as a solvent in proton NMR spectroscopy?

Answer 15

O-H and N-H peaks no longer appear

Question 16

Limitations of gc

Answer 16

Many chemicals have same RT

Similar substances have similar RT’s and so one may hide under another

Unknown substances don’t have RT

Question 17

How is separation achieved

Answer 17

Separation is achieved by relative absorption of substances with the stationary phase

Question 18

What is the way to lay out a 5+ marker on spectroscopy for full marks?

Answer 18

1st column: 'Peak'
2nd column: ' Chemical shift, ppm'
3rd: 'Peak Area,' no. of protons for chem environment
4th: 'Type of Proton' from data sheet
5th: 'Splitting Pattern'
6th: 'No. of Adjacent protons'