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FINISHED > C7.5 Chromatography > Flashcards

C7.5 Chromatography Flashcards

1
Q
  1. What happens in chromatography?
A

-substances are separated by movement of a mobile phase through a stationary phase

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2
Q
  1. What is chromatography?
A
  • an analytical method used to separate substances in a mixture
  • can identify substances
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3
Q
  1. What does mobile phase mean in chromatography?
A
  • liquid or gas

- molecules can move

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4
Q
  1. What does stationary phase mean in chromatography?
A
  • solid or thick liquid

- molecules can’t move

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5
Q
  1. What happens to chemicals in chromatography regarding phases?
A
  • components in mixture separate as mobile phase moves across stationary phase
  • molecules of chemical constantly move between phases
  • move different speeds depending on attraction to different phase (stationary= slower, mobile= faster)
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6
Q
  1. What affects the amount of time molecules spend in each phase?
A
  • how soluble they are to the solvent (mobile phase/higher= more)
  • how attracted the are to the paper (mobile phase/higher= less)
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7
Q
  1. What is there between the stationary and mobile phases for each component in a sample?
A
  • for each component in a sample there is a dynamic equilibrium between the stationary and mobile phases
  • stationary phase→mobile phase = mobile phase→stationary phase
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8
Q
  1. What does a separation by chromatography depend on?
A

-the distribution of the components in the sample between the mobile and stationary phases

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9
Q
  1. What is the use of standard reference materials in chromatography?
A
  • to check the identities of substances

- they have carefully controlled concentration and purities

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10
Q
  1. What happens in paper chromatography?
A
  • substance put on baseline of paper
  • placed in beaker of solvent
  • solvent moves up paper
  • chemicals in sample dissolve in solvent and move between solvent and paper= equilibrium between solvent an paper
  • mobile phase= chemicals move up paper with solvent
  • paper removed from beaker before solvent reaches top of paper
  • chemicals form different spots on paper (mobile phase>stationary phase= further up)
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11
Q
  1. What are the mobile phases and stationary phases in paper chromatography?
A
  • mobile phase: solvent e.g. ethanol, water

- stationary phase: chromatography paper e.g. filter paper

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12
Q
  1. What is the difference between paper and thin-layer chromatography?
A

Paper chromatography

  • mobile phase: solvent e.g. ethanol, water
  • stationary phase: chromatography paper e.g. filter paper

Thin layer chromatography

  • mobile phase: solvent e.g. ethanol, water
  • stationary phase: thin layer of solid e.g. silica gel spread on a glass plate
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13
Q
  1. What are Rf values?
A

-the ratio between the distance travelled by dissolved substances (the solute) and the distance travelled by the solvent

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14
Q
  1. What is the use of locating agents in paper and thin-layer chromatography? (and example)
A
  • in case the spots on the chromatogram are colourless

- e.g. spray chromatogram with reagent

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15
Q
  1. What is gc?
A

-gas chromatography

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16
Q
  1. What are the different phases in gas chromatography?
A
  • mobile phase: unreactive gas e.g. nitrogen

- stationary phase: viscous (thick) liquid e.g. oil

17
Q
  1. What is the process of gas chromatography?
A
  • unknown substances vaporised if not already gases
  • mixture injected into tube coated with stationary phase
  • mixture moves along mobile phase
  • substances are distributed between phases
  • time taken to travel through tube= retention time
  • different chemicals= different retention times
18
Q
  1. What does the term retention time mean regarding gas chromatography?
A

-retention time is the time it takes for a chemical to travel through the tube

19
Q
  1. What is a chromatogram from gc?
A

-graph made in gc for retention times

20
Q
  1. What information can we get from chromatograms for gc?
A
  • distance across y axis= retention time (identifies substance)
  • peak height= how much of chemical was in sample (y axis)
21
Q
  1. What is a solvent?
A

-a substance that a solute dissolves in to form a solution

22
Q
  1. How is an aqueous solution formed?
A

-if solvent is water

23
Q
  1. How is a non-aqueous solution formed?
A

-if solvent is not water

24
Q
  1. What are examples of non-aqueous solvents?
A

-alcohol, acetone

FINISHED (11 decks)

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