Brainscape's Knowledge GenomeTM

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


See full index

Chem Lab > Chromatology: videos > Flashcards

Chromatology: videos Flashcards

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

Define chromatography

A

Method of analyzing and purifying organic compounds based on polarity differences
passing a mixture which contains

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

Name the separation and purification techniques

A

extraction distillation chromatography recrystallization

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

why do polar molecules stay at bottom of plate

A

polar molecules capable of H bond interactions with silica and gets retained

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

What is column chromatography

A

mixture of three compounds: ferrocene, acetyl ferrocene, diacetly ferrocene (iron added for color)

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

Compare mobile and stationary phase

A

compounds to be separates dissolved in a mobile phase (some solvent) through a stationary phase (ex silica) which separates them based on differences of adsorption to the stationary phase

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

describe process of thin layer chromatography

A

uses thin plastic or glass trays coated w adsorbent to identify the composition of pigments, chemicals, or other unknown substances, small amounts

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

describe process of column chromatography

A

uses column filled with adsorbent to separate larger scale mixtures of compounds

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

In TLC mobile phase travels ___ in CLC mobile phase travels ___

A

up
down

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

A distribution equilibrium forms when a compound is either dissolved in a mobile phase or adsorbed in a stationary phase

A

true

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

The longer the mobile phase travels, the better the separation between A and B

A

true

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

stationary phases are usually very polar, while mobile phases vary widely in polarity

A

true

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

If cmpd B spends more time in mobile phase than compound A, B will move further along the direction of flow than A and will eventually be separated in space from A

A

true

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

In TLC, silica fel and alumina are the most common solid adsorbents

A

true

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

How does UV light detection work in TLC?

A

cmpds containing benzene rings or conjugated systems usually absorb light in IV region of electromagnetic spectrum.

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

HOw does chemical staining with idodine work?

A

non destructive
few crystals of iodine placed in closed chamber collect iodine on the spots by weak electrostatic attraction
will form yellow or brown complex except for saturated hydrocarbons or alklyl halides

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

TLC analysis yields an Rf value of less than 0.10 for the cmpd to be separated. How should the mobile phase be modified to increase Rf value?

A

increase polarity of solvent by using more ethyl acetate

17
Q

What is column chromatography

A

technique for purification of synthetic or natural products by polarity differences

variety of adsorbents can be used as stationary phase, silica gel most common(very poalr)

alumina is also used

18
Q

The adsorbent is applied to column in two ways which are

A

slurry/wet packing
dry packing

19
Q

loading sample, wet application

A

dissolve sampl ein small amount of initial mobile pahse and apply by long pipette to top of column

drain eluent from column until no sample remains above surface of sand. Good method but in many cases samples not soluble in initial mobile phase

20
Q

True or False: chromatography involves a mobile and stationary phase

A

truen

21
Q

true or false: non polar molecules will have a low Rf

A

false

22
Q

true or false: mobile phase is often a mixture of polar and nonpolar organic solvents

A

true hexane/ethyl acetate

23
Q

a student develops a TLC of green food dye. After 12 minutes the solvent moved up 10cm and blue spot has advanced 6 cm from origin. After 14 mins the solvent moved a further 5 cm. How far will blue be from origin?

A

you can ignore the time
Rf=Y/X 6cm/10cm= 0.6
x/(10+15)=?
0.6/10cm=X/15
X=9cm

24
Q

while eluting the sample, add more solvent as necessary. Always start with a less polar solvent, slowly increasing polairty

A

true

25
Q

Define isocratic system

A

same composition mobile phase froms tart to finish

26
Q

define gradient system

A

polarity of system increased gradually during separation by increasing proportion of more polar solvent. typical gradient may be started with hexane, then hexane/ethyl acetate mixtures w gradual increase of % of ethyl acetate until all spots are eluted from system

27
Q

define polarity of compounds

A

the more polar the functionality, for example carboxylic acid amine and alcohol the more polar the cmpd

28
Q

in a column chromatography experiment of cholesterol, 1,4-napthoquinone, anthracene, and 4-nitroaniline are purified. Which compound is the least polar?

A

know the structures
one (ketone), ine (amine), ol (alcohol)
ene=alkene, hydrocarbon, so least polar

Chem Lab (3 decks)

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