Chromatography

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  • Created by: J.E.C.
  • Created on: 14-04-14 13:37
All chromatography depends on the ___ set up when a compound distributes itself between two phases? The ___ phase stands still and the ___ phase moves over it?
Equilibrium. Stationary, mobile.
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Different compounds distribute themselves between the two phases to ___ ___, so move along the mobile phase at ___ ___?
Differing extents, different speeds
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Briefly describe how you would carry out TLC?
Spot a small sample of mixture onto a solid support material placed in a suitable solvent. The solvent now rises up the plate. There should be a series of spots present up the plate. If the spots not coloured use UV light or Iodine: locating agent.
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If a compound has a greater affinity for the stationary phase, it does not...?
Get carried as far by the mobile phase.
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The compound is said to be ___ onto the surface of the stationary phase?
Adsorbed
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If a compound has a greater affinity for the mobile phase, it...?
Gets carried further.
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The distance a substance travels in paper or TLC depends on what 3 things?
1. The nature of the substance 2.Total distance travelled by the solvent front 3.Conditions under which the chromatography is carried out (temp, type of plate/solvent).
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What is the Rf value?
The distance that the substance travels relative to the solvent front.
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Rf values are constant for a particular set of conditions, so...?
We can use them to identify the different spots on a chromatogram.
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What do the distances a and x represent?
a: distance between spot of substance A and base line. x: distance from base line to top of solvent front
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Rf value is equal to...?
a/x
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The mobile phase in g.l.c is a...?
Unreactive gas called the carrier gas.
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The stationary phase in g.l.c. is...?
Small amount of high boiling point liquid held on a finely divided inert solid support. This is packed into a long thin tube called a column.
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The column is coiled inside __ ___? The components of the mixture are carried through the column in a..?
An oven. Stream of gas.
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The most volatile compounds usually emerge ___?
First
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A ___ on the outlet tube monitors the compounds coming out of the column and signals from the detector are plotted by a ___ as a ___?
Detector, recorder, chromatogram
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What is meant by 'retention time'?
The time that a compound is held on a column under given conditions.
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Give 4 things that can affect retention time?
1. Packing of the column 2.Nature of carrier gas 3.Flow of carrier gas 4.Temperature of column
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The area under each peak depends on...? If the peaks are very sharp, their ___ ___ can be used?
The amount of compound present. Relative heights
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Other cards in this set

Card 2

Front

Different compounds distribute themselves between the two phases to ___ ___, so move along the mobile phase at ___ ___?

Back

Differing extents, different speeds

Card 3

Front

Briefly describe how you would carry out TLC?

Back

Preview of the front of card 3

Card 4

Front

If a compound has a greater affinity for the stationary phase, it does not...?

Back

Preview of the front of card 4

Card 5

Front

The compound is said to be ___ onto the surface of the stationary phase?

Back

Preview of the front of card 5
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