Brainscape's Knowledge GenomeTM

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


See full index

Chemistry Module 6 > Chromatography > Flashcards

Chromatography Flashcards

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

What are the 2 sections of a TLC plate?

A 
Solid support (sheet of plastic/glass)
Stationary phase (silica gel/aluminium oxide - solid)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What word is associated with the stationary phase in TLC?

A

Adsorption

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

What are the 2 phases in TLC?

A

Stationary phase - solid

Mobile phase - liquid

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

What is the mobile phase in TLC?

A

Carefully picked solvent

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

What word is associated with the mobile phase in TLC?

A

Solubility

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

How do you prepare the TLC plate before starting the chromatography?

A

In pencil draw a baseline 1 cm from the bottom of the plate and X’s on that baseline where the spots of solutions will start.
Put spots of what you are testing on the plate, making sure the spots don’t overlap. The spots must be a solution so dissolve any solids in solvent first. Use a spotting tube - spot each chemical on it’s cross 2-4 times.

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

When you have prepared the TLC plate how do you carry out the experiment?

A

Fill a beaker will solvent, making sure the solvent is lower than the baseline of the TLC plate.
Place the TLC plate in the solvent and cover the beaker with clingfilm.

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

Why do you cover the beaker in TLC chromatography?

A

Saturates the space with solvent. Chemicals move in a straighter line.

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

How long must you wait in TLC while the solvent moves up the plate?

A

5-55 minutes - until the solvent is about 1 cm from the top of the plate.

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

What must you do when the solvent is 1 cm from the top of the plate in TLC?

A

Remove it quickly and mark where the solvent reached - Draw a pencil line (called the solvent front)

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

What must you do once drawing the solvent front in TLC?

A

Leave plate to dry / use a hairdryer to dry it

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

What must you do in TLC after letting the plate dry?

A

Develop the plate (3 ways)

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

What are the 3 ways to develop a TLC plate?

A

UV light
Ninhydrin (spray or dip)
Iodine crystals

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

What is the Rf value?

A

Retention Factor = Distance moved by compound / Distance moved by solvent

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

What are the uses of TLC?

A

Test purity (compare Rf values to a pure sample)
Identify compounds in a mixture
Identifying chemicals (compare Rf to database of known values)
Collect compounds - large scale

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

What are the limitations to TLC?

A

Similar components - similar Rf values.
Big spot can cover small spot
Difficult to find solvent that separates all components
unknown chemical - no Rf value on database

17
Q

In terms of solubility what would you say if dot A moved further up the TLC plate than B?

A

A has a greater solubility in the mobile phase than B

18
Q

In terms of adsorption, what would you say if dot A moved further up the TLC plate than B?

A

A has a weaker adsorption in the stationary phase than B

19
Q

What is the mobile phase in gas-liquid / gas-solid chromatography?

A

Inert gas carrier

20
Q

What is the stationary phase in gas-liquid / gas-solid chromatography?

A

High boiling point alkane (liquid or solid)

21
Q

Why is the stationary phase in gas-liquid / gas-solid chromatography a high boiling point alkane?

A

So it doesn’t evaporate in the oven

22
Q

What word is used with a liquid stationary phase in gas-liquid chromatography?

A

Solubility

23
Q

What word is used with a solid stationary phase in gas-solid chromatography?

A

Adsorption

24
Q

What are the uses of gas-liquid / gas-solid chromatography?

A 
Get retention time
Compare to a database of known values to identify components.
Separate a mixture.
Link to mass spectroscopy.
Find concentration of a solution
25
Q

What is retention time?

A

Time taken for a component to travel from injection (start of column) to the detector. The recorder then produces a graph called a chromatogram.

26
Q

What does the centre of a peak on a chromatogram show?

A

The retention time

27
Q

What happens to the size of the molecule as retention time increases?

A

Get larger - greater solubility / adsorption to stationary phase

28
Q

What does the area under the peak show in a chromatogram?

A

The amount of each component

29
Q

What are the limitations of gas-liquid / gas-solid chromatography?

A

Large peak can cover small peak.
Similar components have similar RT values - difficult to identify.
Unknown compound - no comparison.

30
Q

How do you use gas-liquid / gas-solid chromatography to work out the concentration of a solution?

A

Make standard solutions of known concentrations (2, 4, 6, 8. 10 moldm^3).
Run GC, amount of A in each is area under peak.
Draw calibration curve graph (conc and area under peak).
Run GC on unknown and find area under peak
Read off calibration curve.

Chemistry Module 6 (10 decks)

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