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AQA Chemistry > 3.16 Chromatography > Flashcards

3.16 Chromatography Flashcards

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1
Q

What are the basic principles of chromatography?

A

Seperation technqiues in which a mixture is separated if dissolved in solvent (mobile phase) and passed over a solid (stationary phase)

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2
Q

What is meant by the mobile phase?

A

Carries the soluble components of a mixture

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3
Q

What makes components move faster?

A

Solubility
Affinity to the solvent

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4
Q

What is meant by the stationary phase?

A

Holds back components of mixture attracted to it

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5
Q

How are substances separated by chromatography?

A

Balance between affinity for mobile phase and stationary phase different for every component meaning they move at different rates

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6
Q

Why will different substances show different Rf values?

A

Bonded differently and have different polarities
More polar bonds = smaller Rf value

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7
Q

Which phase are hydrogen bonding/dipoles attracted to?

A

Stationary phase

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8
Q

What does TLC stand for?

A

Thin Layer Chromatography

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9
Q

What is the stationary phase in TLC?

A

Plastic/glass/metal sheet or “plate” coated in silica or alumina

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10
Q

What are the advantages of TLC over paper chromatography?

A

Runs faster
Smaller amount of mixture required
TLC plates more robust

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11
Q

How can colourless spots be observed in TLC?

A

UV light
Developing agent (ninhydrin + heat)

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12
Q

How is Rf value calculated?

A

distance moved by component
÷
distance moved by solvent front

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13
Q

What does Rf value mean?

A

Retention factor
A ratio between rate of movement of solvent and component

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14
Q

How can the identity of a substance be confirmed by its Rf value?

A

Comparison with accepted Rf values for that substance run in the same solvent and set up

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15
Q

What is column chromatography?

A

Column packed with silica, alumina or resin has solvent run down through it

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16
Q

What is the stationary phase of column chromatography?

A

Silica, alumina or resin packed into column

17
Q

What is the mobile phase in column chromatography?

A

Eluent
The solvent added at the top that runs down

18
Q

What are the advantages of coumn chromatography?

A

Better separation as more than one eluent can be used
Fairly large amounts can be separated and collected

19
Q

What is the stationary phase in gas-liquid chromatography?

A

Powder coated will oil packed into a long thin capillary tube that is coiled and placed in oven

20
Q

What is the mobile phase in gas-liquid chromatography?

A

Carrier gas

21
Q

What is measured in gas-liquid chromatography?

A

Retention time
Different mixtures taken different times to move through

22
Q

What are the advantages of gas-liquid chromatography?

A

Very sensitive even to minute traces

23
Q

What are the uses of gas-liquid chromatography?

A

Drugs testing

24
Q

How can gas-liquid chromatography be used to identify substances?

A

Match gas chromatograph to that of a known substance in same conditions
Retention time should be an exact match

25
Q

What is GCMS?

A

Gas Chromatography-Mass Spectrometry

26
Q

How does Gas Chromatography-Mass Spectrometry work?

A

Gas chromatography is run, retention time recored
Mixture run through mass spectrometer
Fragmentation patterns confirms identity

AQA Chemistry (8 decks)

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