Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry > chromatography ch 13 > Flashcards

chromatography ch 13 Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

chromatography

A

a set of techniques that can be used to separate and analyse the components in a mixture.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How is chromatography performed?

A

by passing a mixture through a medium (material) that allows the components of the mixture to move through at different rates.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

thin layer chromatography (TLC)

A

similar to paper chromatography, but uses a thin layer of a powder such as alumina spread on a glass plate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

high performance liquid chromatography (HPLC)

A

a very sensitive type of column chromatography.
It uses very small particles in the column’s solid.
It uses UV to detect the components.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

gas chromatography (GC)

A

A very sensitive technique that uses a gas like nitrogen as the mobile phase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

components

A

parts of a mixture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

the pattern of bans or spots

A

chromatogram

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

paper chromatography

A

chromatography that uses paper as a stationary phase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

column chromatography

A

a technique in which the stationary phase is in a column.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what states of matter can be a mobile phase?

A

liquid or gas.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

desorption

A

opposite of adsorption.

molecules come away from the stationary phase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

chroma+ graphy greek)

A

colour writing

Khromatos + graphos

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

If a piece of chalk is dipped in ink and then placed in water:

a. what is the stationary phase?
b. what is the mobile phase?

A

a. the chalk

b. the water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

the ability of the mobile phase to stick to the stationary phase, depends on the ______ of the two materials

A

polarity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

the ability of the mixture to dissolve in a solvent depends on the _________ of the mixture and the solvent.

A

polarity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

the rate of movement of each component depends mainly on: (2)

A
  1. how strongly the component absorbs onto the stationary phase.
  2. how readily (easily) the component dissolves in the mobile phase.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

why do the components separate in chromatography?

A

the components bond with the stationary phase and mobile phase in different amounts.
e.g. blue in moves faster because is more soluble in water than the red dye.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

A student notices that the blue component of the ink moves faster than the red component.
What does this tell you about the bonding between the blue dye and the paper?

A

The bonds between the particles of the blue dye bond weakly with the paper, compared to the red dye.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

A student notices that the blue component of the ink moves faster than the red component.
What does this tell you about the bonding between the blue dye and the paper vs the red dye and the paper?

A

The bonds between the particles of the blue dye bond weakly with the paper, compared to the red dye.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

If a drop of black ink is placed near the bottom of a strip of paper and is placed in water and left for 30 minutes, a blue band moves quickly down the paper and a red band moves much more slowly.
What does this tell you about the polarity of the blue and red ink?

A

The blue dye bonds with the water better than the red dye, so it is more polar than the red dye.
Water is a polar solvent so dissolves polar molecules well.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Paper and thin layer chromatography are used for Q_______ analysis.

A

QUALITATIVE ( what is present, not how much).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Who developed chromatography?

A

Mikhail Tsvet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

origin

A

the position of the spot of mixture on a paper or thin layer plate.

24
Q

solvent front

A

the upper edge of the solvent as it rises up the paper.

25
Q

calibration curve

A

a plot of data involving two variables that is used to determine the values for one of the variables.

26
Q

carrier gas

A

an unreactive gas , often nitrogen, used in a gas chromatograph.

27
Q

eluent

A

the solvent that carries the components and passes through a chromatography column.

28
Q

injection point

A

opening through which the sample is injected into a gas chromatograph.

29
Q

qualitative analysis

A

an analysis to determine the IDENTITY of the chemical(s) present in the mixture.

30
Q

quantitative analysis

A

an analysis to determine the concentration (AMOUNT) of the chemicals present in a mixture

31
Q

retardation factor

A

the ratio of the distance a component has moved from the origin to the distance the solvent has moved from the origin.

32
Q

retention time

A

the time taken for a component to pass through a chromatography column.

33
Q

standard solution

A

a solution that has an accurately known concentration.

34
Q

Why must the origin be above the level of the solvent?

A

So that the components move up the paper and not dissolve in the solvent.

35
Q

What two factors affect how the mixture’s components travel up the paper or column?

A
  1. the component’s attraction to the stationary phase.

2. the component’s solubility in the solvent.

36
Q

What are the two ways a component can be identified?

A
  1. Compare unknown to a standard of a known chemical.
    e. g. compare unknown to a specific ink chromatgram.
  2. Calculate the retardation factor (Rf) of the sample and compare it to a table of Rf values.
37
Q

Method 1 Using standards to identify an unknown component.

What do you need to know for this method to be useful?

A

You must have an idea of what might be present.

These will be the standards you will use.

38
Q

Why does the standard method require the known and unknown to be on the same paper?

A

So the rate of movement can be directly compared.

39
Q

Rf or Retardation factor

A

distance the solvent front travelled from the origin

40
Q

Rf values will always be less than ____

A

1

41
Q

the component that moves the least, (slowest) has the ________ Rf value.

A

smallest / lowest value.

42
Q

The conditions of method 2 must be the same because…

A

otherwise the unknown cannot be compared to the values in the table.

43
Q

Why are ultraviolet lights used in chromatography?

A

Because most components are colourless, but they will fluoresce under UV light.

44
Q

What is ninhydrin used for?

A

to make the components fluoresce under UV light.

45
Q

why are paper and thin layer chromatography only used as guides to what is present?

A

Many other components may have that Rf value.

46
Q

List 2 advantages for paper chromatography

A

cheap
little prep
more efficient for polar and water soluble compounds
easy to handle and store

47
Q

List 2 advantages for thin layer chromatography

A

detects smaller amounts
better separation of less polar compounds
corrosive materials may be used
a wide range of stationary phases (powders) are available.

48
Q

Why is HPLC useful?

A

Very sensitive.

e.g. drugs in blood

49
Q

How much smaller are the particles in HPLC that in regular column chromatography>

A

10-20 times smaller.

50
Q

Why does HPLC have very small particles?

A

allows the components to adsorb and desorb to the solid phase easier.
This makes the components separate more completely.

51
Q

Why does HPLC need high pressure?

A

The small particles put up a lot of resistance.

52
Q

Which is the most sensitive form of chromatography?

A

gas

53
Q

What is the main problem with gas chromatography?

A

you can only use substances that won’t break apart when vapourised.

54
Q

What type of chromatography is used to detect drugs in urine?

A

gas

55
Q

What two questions can HPLC and GC answer?

A
  1. what is present

2. how much is present.

Chemistry (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions