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orgchem lab > Chromatography > Flashcards

Chromatography Flashcards

1
Q

It is used separate mixtures of compounds and identify an unknown

A

Chromatography

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2
Q

Chromatography exploits the differences in ________ and _______

A

Solubility and Adsorption

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3
Q

Compounds are separated based on the way they interact with a porous material called the (1.____), and the solvent that moves the mixture through the adsorbent, called the (2.______)

A
  1. Adsorbent or Stationary Phase
  2. Eluent or Mobile Phase
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4
Q

TRUE OR FALSE:

Mobile phase may be a liquid or a gas

A

TRUE

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5
Q

TRUE OR FALSE:

Stationary phase is typically a solid

A

True

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6
Q

TRUE OR FALSE:

As the mobile phase flows over the stationary phase, the components in the mixture are carried along

A

TRUE

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7
Q

It uses a solid stationary phase and a liquid mobile phase

A

Adsorption Chromatography

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8
Q

Separation is governed by ____________ phenomena

A

Surface Adsorption

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9
Q

It refers to the ability of a substance to ‘stick’ (or be adsorbed) to a surface.

A

Adsorption

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10
Q

TRUE OR FALSE:

The adsorbent is the molecules of interest while the adsorbate is the surface.

A

FALSE
Adsorbent - surface
Adsorbate - molecules of interest which are getting adsorbed on the adsorbent.

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11
Q

Partition Chromatography is governed by ____________ of the sample in the stationary and mobile phase.

A

Differences in the solubility

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11
Q

TRUE OR FALSE:

The mixture to be separated is adosrbed on the solid stationary phase over which the liquid mobile phase is allowed to flow.

A

TRUE

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11
Q

The extent of adsorption of a single component depends on:

A
  1. Polarity of the Molecule
  2. Activity of the Adsorbent
  3. Polarity of the Liquid Mobile Phase
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12
Q

Separation is based on ________ partitioning between two liquid phases (relative solubility)

A

solute

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12
Q

TRUE OR FALSE:

In general, the more polar a functional group in the compound is, the more strongly it will be adsorbed on the surface of the polar stationary phase, the slower it will be transported by the mobile phase.

A

True

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13
Q

TRUE OR FALSE:

At equilibrium,
K = compound in the stationary phase ⇌ compound in mobile phase

A

TRUE

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14
Q

It is a form of solid-liquid adsorption chromatography.

A

Thin Layer Chromatography

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14
Q

It uses a liquid stationary phase supported on the surface of a solid and a liquid or gas mobile phase which is insoluble in the stationary phase.

A

Partition Chromatography

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15
Q

Thin Layer Chromatography uses a 1. ________ supported 2. ________ as the solid phase.

A
  1. Thin Layer of Adsorbent (usually alumina/silica gel)
  2. Flat Surface (usually glass)
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15
Q

TRUE OR FALSE:

The mobile phase is a solute chosen according to the properties of the components in the mixture

A

FALSE; mobile phase is a solvent

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16
Q

Silica gel is a ________ that can hydrogen bond.

A

Polar Adsorbent

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17
Q

TRUE OR FALSE:

Non-polar compounds will move faster and migrate further up the TLC plate.

A

TRUE

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17
Q

TRUE OR FALSE:

Components of the mixture that are polar and/or can hydrogen bond will interact more with the silica gel and hence move less quickly up the TLC plate.

A

TRUE

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18
Q

Technique for separating dissolved chemical substances by taking advantage of their different rates of migration across sheets of paper.

A

Paper Chromatography

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18
Q

TRUE OR FALSE:

The solvent penetrates the paper by capillary action and, in passing over the sample spot, carries along with it
the various components of the sample

A

TRUE

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18
Q

Used to
* Identify compounds or unknown mixtures
* Detecting intermediates in reactions, determine their purity
* Determine the progress of a reaction
* Determining the number of components in a mixture
* Evaluating the efficiency of purification processes .

A

Thin Layer Chromatography

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19
Q

Made of highly purified cellulose absorbs and retains water molecules strongly constitute the stationary phase.

A

Filter paper

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20
Q

Point where the sample is initially spotted on the paper.

A

Baseline or Origin

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21
Q

The distance moved by the solvent along the paper

A

Solvent Front

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22
Q

TRUE OR FALSE:

Separation takes place due to the different affinities of the components of the mixture for the polar stationary phase and the mobile phase which is relatively nonpolar solvent or solvent system.

23
Q

It is an example of liquid-liquid partition chromatography

A

Paper Chromatography

24
Q

TRUE OR FALSE:

There is a continuous back-and-forth
exchange of solutes between water and the solvent, but those which are more soluble in the mobile phase spend more time in it and are carried up the paper faster.

25
Q

TRUE OR FALSE:

Paper Chromatography is not used in the rapid analysis of the components of reaction mixtures and as a tentative means of identification

A

FALSE; it is used

26
Q

A substance that separates and moves constituents of a mixture through the column of a chromatograph.

27
Q

Arrange the solvents in order of their increasing polarity:

  • Acetone
  • Chloroform
  • Cyclohexane
  • Ethanol
  • Methanol
  • Petroleum Ether
  • Toluene
A

Least Polar
* Petroleum Ether
* Cyclohexane

Increasing Polarity
* Toluene
* Chloroform
* Acetone
* Ethanol

Most Polar
* Methanol

28
Q

A characteristic property given compound in a given solvent on a particular stationary phase

A

Retention Factor (Rf)

29
Q

TRUE OR FALSE:

A particular compound will travel the similar distance along the stationary phase by a specific solvent (or solvent mixture) given that other experimental conditions are kept constant.

A

FALSE; it will travel the different distance

29
Q

TRUE OR FALSE:

The distance traveled by a compound is obtained by
measuring the distance from the origin to the point of greatest density (center of mass) of the spot corresponding to the compound.

30
Q

TRUE OR FALSE:

Obtain a TLC plate. Handle it only at its corners.

31
Q

Using a pencil, lightly draw a thin line parallel to one side ~ ____ from the bottom.

32
Q

Draw an ____________ of the ink sample into a capillary tube and spot on the line of a TLC plate just once.

33
Q

TRUE OR FALSE:

To save time and materials, practice your spotting
techniques on a piece of scratch paper before attempting to use the chromatographic strip. Make sure that the spot does not exceed two millimeters in diameter.

33
Q

TRUE OR FALSE:

The spot must be very small and not too concentrated to get a good separation.

34
Q

In a wide-mouth screwcap bottle, pour about ____ the solvent system (6:2:2 (v/v/v n-butanol-ethanol-2N NH3).

35
Q

TRUE OR FALSE:

For the step 4 of Analysis of the Component Dyes of Black Ink by TLC:
Spot the other plate using another ink brand

36
Q

TRUE OR FALSE:

Line the sides of the chamber with a piece of filter paper
and allow the system to equilibrate.

37
Q

TRUE OR FALSE:

For the step 6 of Analysis of the Component Dyes of Black Ink by TLC:

After about two minutes, place the TLC plates in the
developing chamber. Cover the chamber tightly. Label the chamber with your group number and leave it in the hood

38
Q

TRUE OR FALSE:

The solvent must be above the baseline

A

FALSE; must be below

39
Q

TRUE OR FALSE:

For the step 7 of Analysis of the Component Dyes of Black Ink by TLC:

Allow the chromatogram to develop (about 20 minutes)

40
Q

TRUE OR FALSE:

For the step 8 of Analysis of the Component Dyes of Black Ink by TLC:

When the solvent front is about one inch from the top of
the plate, remove the TLC plate from the chamber and mark the solvent front with a pencil.

41
Q

TRUE OR FALSE:

You should not allow the plate to dry.

A

FALSE; you should allow

42
Q

TRUE OR FALSE:

For the step 10 of Analysis of the Component Dyes of Black Ink by TLC:

Mark the outline of the individual spots with a pencil. Copy the pattern produced on your data sheets and label each spot according to its color

43
Q

TRUE OR FALSE:

For the step 11 of Analysis of the Component Dyes of Black Ink by TLC:

Compare and analyze the chromatograms produced by the two brands of ink as to the number of dyes, colors and relative positions. Note which dyes in each ink move the same distance.

44
Q

For the Step 1 of Identification of Amino Acids by Paper Chromatography

Obtain a clean sheet of ____________, about 12cm by 18cm.

A

Whatman No.1 Filter Paper

45
Q

Lightly place 8 X’s along the line at ________

A

2 cm intervals

45
Q

Using a pencil, lightly draw a thin line parallel to one side, ________ from the edge of the paper.

46
Q

Under each X, place an identifying mark, two for each standard (P= ________ , T= __________ , and A = __________ ) and two for the ___________ (U)

A
  • P = phenylalanine
  • T = tyrosine
  • A = aspartic acid
  • U = unknown substance
47
Q

TRUE OR FALSE:

Spot a small amount each solution on its designated
position on the paper. Do this five times allowing the spot to dry each time.

48
Q

TRUE OR FALSE:

For the step 6 of Identification of Amino Acids by Paper Chromatography:

Roll the paper into a cylinder and staple the ends as shown below. Make sure that the edges of the paper do not touch each other..

48
Q

For the step 7 of Identification of Amino Acids by Paper Chromatography:

Fill the developing chamber with the solvent system (1:2 (v/v) 2% ammonium hydroxide-isopropyl alcohol) up to __________

A

0.75 cm deep.

49
Q

TRUE OR FALSE:

For the step 8 of Identification of Amino Acids by Paper Chromatography:

Slowly place the cylindrical paper in the chamber observing the usual precautions

50
Q

TRUE OR FALSE:

For the step 9 of Identification of Amino Acids by Paper Chromatography:

Cover the chamber tightly and allow the chromatogram to develop (about 1 and ½ hours). Leave the chamber and the paper undisturbed.

51
Q

TRUE OR FALSE:

For the step 10 of Identification of Amino Acids by Paper Chromatography:

After the chromatogram has been developed, open the
chamber and carefully remove the paper.

52
Q

TRUE OR FALSE:

For the step 11 of Identification of Amino Acids by Paper Chromatography:

Take out the staples and spread the chromatogram out on a paper towel

53
Q

TRUE OR FALSE:

For the step 12 of Identification of Amino Acids by Paper Chromatography:

Immediately mark the solvent front lightly with a pencil.

54
Q

TRUE OR FALSE:

For the step 13 of Identification of Amino Acids by Paper Chromatography:

Allow the paper to dry completely. A hair dryer or an oven at about 80C may be used to speed up the drying process.

55
Q

For the step 13 of Identification of Amino Acids by Paper Chromatography:

Dip the paper in a ________ in acetone. Do this under the hood. Distinct colored spots will appear as the ninhydrin reacts with the amino acids.

A

2% ninhydrin solution

56
Q

TRUE OR FALSE:

Ninhydrin is neurotoxin. Avoid direct skin contact. Do
not inhale the fumes.

57
Q

TRUE OR FALSE:

For the step 15 and 16 of Identification of Amino Acids by Paper Chromatography:

Allow the solvent to evaporate and place the paper in an oven at 100-110C for about 10 minutes.

58
Q

What is the step 17 of Identification of Amino Acids by Paper Chromatography?

A
  1. Encircle each spot with a pencil and calculate the Rf values.
59
Q

TRUE OR FALSE:

For the step 18 of Identification of Amino Acids by Paper Chromatography:

Compare the color and Rf values produced by the unknown amino acid to those of the known samples.

60
Q

What is the last step (Step 19) of Identification of Amino Acids by Paper Chromatography?

A

Identify the unknown amino acid

orgchem lab (9 decks)

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