Chapter 29 - Chromatography and Spectroscopy Flashcards Preview

OFFICIAL OCR A-Level Chemistry > Chapter 29 - Chromatography and Spectroscopy > Flashcards

Flashcards in Chapter 29 - Chromatography and Spectroscopy Deck (18)
Loading flashcards...
1
Q

What are the two phases for all forms of chromatography?

A

Stationary phase

Mobile phase

2
Q

What is the stationary phase?

A

Does not move

A solid or a liquid supported on a solid

3
Q

What is the mobile phase?

A

Does move

Normally a liquid or a gas

4
Q

What is a TLC plate made of?

A

Plastic/glass sheet

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

5
Q

Outline adsorption in reference to TLC

A

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

6
Q

How is the retention factor calculated?

A

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

7
Q

What is gas chromatography useful for?

A

Separating and identifying volatile organic compounds present in a mixture

8
Q

What are the different phases for gas chromatography?

A

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

9
Q

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

A

Moves slower

Time taken increases

10
Q

What is retention time?

A

Time taken for a component to travel through the column

11
Q

How is retention time used for identification?

A

Compare to retention times in database

12
Q

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

A

Concentrations of components in the sample

13
Q

What is resonance for NMR?

A

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

14
Q

What is the standard reference chemical for NMR?

A

Tetramethylsilane (TMS)

(CH3)4Si

15
Q

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

A

O-H and N-H peaks no longer appear

16
Q

Limitations of gc

A

Many chemicals have same RT

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

Unknown substances don’t have RT

17
Q

How is separation achieved

A

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

18
Q

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

A
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'