question

____ a method of separating mixtures into their pure components

answer

Chromatography

question

chromatography: a method of _____

answer

separating mixtures into their pure component

question

Chromatography separates mixtures because the ____ between the various components of the mixture and the stationary phase are different

answer

intermolecular attractions

question

Chromatography separates mixtures because the intermolecular interactions between the ____

answer

various components of the mixture and the stationary phase are different

question

Chromatography is a method of separation using a ___ and a ____

answer

stationary phase; mobile phase

question

separation occurs as the mobile phase ____ the stationary phase

answer

passes over

question

the mobile phase can be ___ or ___

answer

liquid; gas

question

the stationary phase can be ___ or ___

answer

solid; liquid

question

Chromatography-Basic Principle: same basic principle as TLC but now ____ of pressure (_____) to ___ compounds

answer

use gravity; medium to high; elute

question

Chromatography is both a ____ and ____ method

answer

qualitative; quantitative

question

Chromatography is used for _____ the course of a reaction

answer

monitoring

question

Chromatography is used for monitoring ____

answer

the course of a reaction

question

3 types of chromatography used for monitoring the course of a reaction

answer

thin layer chromatography; gas chromatography; high performance liquid chromatography

question

what does TLC stand for

answer

thin layer chromatography

question

what does GC stand for

answer

gas chromatography

question

what does HPLC stand for

answer

high performance liquid chromatography

question

chromatography is used for _____ the components of a reaction

answer

isolating

question

what methods of chromatography are used for isolating the components of a reaction

answer

column chromatography; prep HPLC; Prep TLC

question

Chromatography is both a qualitative and quantitative method used for ___, ___ and ___

answer

1) monitoring the course of a reaction 2) isolating the components of a reaction 3) assisting in the identification of a compound

question

In liquid chromotagraphy ____ is established

answer

equilibrium

question

in the equation for chemical equilibrium what does Xm and Xs stand for

answer

the concentrations of solute molecules in the mobile phase and the stationary phase

question

in the equation for chemical equilibrium what does Sm and Ss stand for

answer

Sm and Ss are for the solvent molecule concentrations

question

in the equation for chemical equilibrium what does the value K represent

answer

the distribution coefficient or equilibrium between the solute and solvent molecules and between the mobile and stationary phases

question

____ values of K will mean a greater capacity to separate

answer

high

question

Interaction at SiO2/Solvent interface: competition exists between _____ and _____ for sites on the _____

answer

polar solvent molecules; polar solute molecules; SiO2 surface

question

Fill in blank on back elute

answer

A mixture of A, B, and C ready to ___ through a column

question

in tlc ______ contains material to be separated

answer

moving phase

question

Separation occurs as ____ passes over the ____. This separation occurs when molecules _____ of the ____ through weak intermolecular forces

answer

moving phase; stationary phase; adhere to the surface; absorbant

question

in moving phase the separation occurs when moleculars adhere to the surface of the absorbant through weak intermolecular forces. These forces are ____ and therefore ____

answer

weak; reversible

question

The eluents can be collected at the _____ as ___

answer

end of the column; individual fractions (cuts)

question

Order of elution: ____ are strongly retained on the ____ and therefore eluted late from the chromatographic columns filled with polar stationary phase

answer

polar compounds; polar stationary phases

question

Order of Elution: polar compounds are strongly retained on the polar stationary phase and therefore are ____ from the ___ filled with ____

answer

eluted; chromatographic columns; polar stationary phase

question

Order of Elution: _____ are strongly retained on _____ and therefore are eluted late from the chromatographic column filled with nonpolar (so called ___) phase

answer

nonpolar compounds; nonpolar stationary phases; reversed

question

nonpolar compounds are strongly retained on nonpolar stationary phases and therefore eluted late from the chromatographic column filled with _____

answer

nonpolar (so called reversed) phase

question

Draw thin layer chromatography where A is more polar than B

answer

(Mobil phase moves upwards)

question

If A is more polar than B. ___ will elute later from a column with polar stationary phase in column chromatography and will _____ with a polar stationary phase (having a lower ____)

answer

A; stay at the origin of the thin layer chromatography plate; Rf

question

what does Rf stand for

answer

retention factor

question

if something has a higher retention factor then in mobile phase it sill ___

answer

not move as far

question

How do you make a capillary pipet

answer

take a capillary tube. Place middle part in flame, rotate until soft. Remove from flame and pull. Score lightly in center of pulled section. Break in half to give two pipets

question

See back page for question? 1st: not polar enough 2nd: satisfactory 3rd: too polar

answer

Which of these solvents is satisfactory?

question

See next page for question Rf(compound 1)=22/65=0.34 Rf(compound 2)=50/65=0.77

answer

What is Rf compound 1? What is Rf compound 2?

question

_____ spots are colored

answer

visualized

question

colorless spots require

answer

I2 vapor; various oxidizing stains such as KMnO4, MoO3, fluorescent indicator in stationary phase (visualized with UV light), special spray reagents

question

What does it mean when Rf=1

answer

spots travel with solvent front

question

Rf=0 what does it mean

answer

spot doesn't move off baseline, undesirable

question

range of Rf values

answer

Rf from 0 to 1

question

what is Rf if spot travels with solvent front

answer

1

question

How to use chromatography to test for purity?

answer

1) Run sample with several solvent systems so that Rf is between 0.2 and 0.5 2) If only one spot appears each time, the sample is probably pure

question

How can we use chromatography to test for identity?

answer

1) run unknown and known with several solvent systems so that Rf is between 0.2 and 0.8 2) if both samples have same Rf each time, they are probably identical

question

The stationary phase is coated on ___

answer

glass or plastic plate

question

The mobile phase flows up the plate by ____

answer

capillary action

question

The ____ flows up the plate by capillary action

answer

mobile phase

question

Binder: ______ is used to help stationary phase stick to plastic or glass surface

answer

hydrogen calcium sulfate

question

Normal phase system: the stationary phase is often ____ or ___

answer

alumina; silica gel

question

in a normal phase system the mobile phase is often ___

answer

organic solvent

question

in a normal phase system the separation mechanism is ___

answer

adsorption

question

4 characteristics of TLC

answer

1) rapid 2) simple 3) requires little sample 4) usually an analytical tool

question

a preparative TLC is not good for ____

answer

separating large (gram) quantities

question

3 uses of TLC

answer

1) purity indicator 2) identification 3) monitoring reactions

question

Why do A, B and C separation

answer

1) chemical nature of A, B, C 2) type of stationary phase 3) mobile phase polarity

question

Different types of chemical nature of A, B, and C which affect separation of compounds.

answer

1) bond-dipoles and polarity 2) hydrogen bonding 3) presence of acidic hydrogens 4) ionic bonds or salts 5) proportion of "polarity" to "grease"

question

What is adsorption?

answer

It is a surface phenomenon. Molecules 'stick' to the surface of a polar solid. "They are said to be absorbed on the surface."

question

adsorption is not the same as ___

answer

absorption

question

Adsorption Chromatography: stationary phase is a ____

answer

solid absorbent

question

3 things which may be used as a solid absorbent

answer

Silica gel (SiO); C18; Alumina (Al2O3)

question

In normal phase chromatography the ___ compound moves faster because ____

answer

least polar; it interacts with the stationary phase to a lesser extent

question

Normal Phase Chromatography: the least polar compound has a ____ retention time and therefore travels ____ the plate. It has a ___ Rf

answer

shorter; farther up; high

question

___ and ___ are common polar stationary phases that will interact strongly via electrostatic interactions with molecules that are ____

answer

SiO2; Al2O3; polar

question

____ is kinda like the opposite of normal-phase chromatography

answer

reverse-phase chromatography

question

In reverse-phase chromatogrpahy ____ interacts strongly with greasy compounds containing lots of saturated and unsaturated _____

answer

C18 backbone; hydrocarbon functionalities

question

R(CH2)nCh3 and other hydrocarbon groups are very ____ functional groups and thus stick to the _____ ,resulting in a ___Rf in reverse phase chromatography

answer

nonpolar; nonpolar stationary phase; Rf

question

In reverse phase chromatography the ____ moves faster, has a____ retention time, travels ___ and has a___ Rf

answer

polar compound; shorter; farther; higher

question

adsorption works because of ____

answer

electrostatic attraction

question

partitioning applies to ___ and ____ chromatography

answer

liquid-liquid; gas-liquid

question

____ applies to liquid-liquid and gas-liquid chromatography

answer

partitioning

question

in ____ compounds distribute between the two immiscible liquid phases

answer

paritioning

question

Solubility differences cause ___

answer

separation

question

_____ cause separation

answer

solubility separation

question

The value ___represents the distribution coefficient or equilibrium of a solute A between the ____

answer

Kp; the two systems Kp=A1/A2 where A1 is amount of A in phase 1 and A 2 is amount of A in phase 2

question

bond dipoles depend on ___, ___ and ___

answer

bond length; charge separation; electronegativity difference

question

a molecular dipole moment is the ____

answer

vector sum of the bond dipole moments

question

____ are heteroatoms with electron pairs, or filled pi-orbitals of double bonds-distribution of electron density can be distorted by a dipole in another molecule (stationary phase)

answer

polarizable groups

question

polarizable groups are _____ with electron pairs, or filled ____ of double bonds. _____ can be distorted by a dipole in another molecule (____)

answer

heteroatoms; pi-orbitals; Distribution; stationary phase

question

hydrogen bonding may cause a ____

answer

strong interaction w/ a stationary phase

question

in order to have hydrogen bonding an organic molecule must have ____ or ___

answer

N-H; O-H

question

the presence of an ___ hydrogen (_____) contributes to making the molecule polar?

answer

acidic; low pKa

question

2 procedure types of column chromatography

answer

gravity; flash

question

3 physical processes for separation

answer

adsorption; partitioning; ion exchange

question

_____ is a chromatographic technique that can separate a mixture of compounds, and is used in chemistry to identify, quantify, and purify the individual components of the mixture

answer

HPLC

question

How does a developing chamber work

answer

You put the solvent in bottom, put the filter paper on the side (solvent goes up the side in order to keep the beaker air full of solvent particles so that none of solvent evaporates off side of filter paper)

question

Why do you use a pencil instead of a pen when drawing the line

answer

b/c if you use pen the ink will spread upwards with the solvent

question

What do you use in order to transfer die onto plate

answer

you use a capillary tube (which makes a small dot)

question

photosynthetic pigments contained in spinach leaves belong to two classes ____ and ____

answer

cartenoids; chlorophylls

question

2 types of cartenoids

answer

cartene; xanthophylls

question

2 types of chlorophylls in experiment

answer

cchlorophyll a and b

question

_____ is the primary pigment that transforms the energy of sunlight into chemical energy oters are ____

answer

chlorophyll a; accessory pigments

question

what do accessory pigments do

answer

help efficiently harvest the light and deliver protons to chlorophyll a

question

_____ via a redox reaction donates an electron into an electron transport chain

answer

accessory pigments

question

____ is chlorophyll lacking the central magnesium ion and serves as a primary electron acceptor and helps initiate the ETC in photosynthesis

answer

phenophytin

question

pheophytin is ____ lacking the _____. It serves as a primary electron acceptor and helps to ___ in photosynthesis

answer

chlorophyll; magnesium ion; initiate the electron transport chain

question

Chlorophyll a has a ____ where chlorophyll b has an ____

answer

methyl group; aldehyde functional group

question

chlorophyll ___ is slightly more polar than chlorophyll __

answer

b; a

question

____ is a hydrocarbon and is therefore very lipophilic and nonpolar

answer

beta-Carotene

question

what is your solvent front?

answer

pretty much how high up the solvent trveled up the paper

question

what might change Rf of same compound

answer

type of solvent u use; temperature

question

when does stationary phase occur for substance

answer

when it is stuck to paper nd not moving

question

when does mobile phase occur for a substance

answer

when it is free moving, not stuck to paper

question

molecules are constantally moving back and forth between free and absorbed stages. What effects this equilibrium

answer

1) polarity and size of moleculle 2) polarity of the stationary phase 3) polarity of the solvent

question

list following from eluted first to last chlorophyll b, chlorophyll a, beta carotene, violaxanthan, zeaxanthin, lutein

answer

beta carotene; chlorophyll a; chlorophyll b; lutein; zeaxanthin; violaxanthan

question

ethanol chemical formula

answer

CH3Ch2OH

question

ethyl acetate chemical formula

answer

C4H8O2

question

hexane chemical formula

answer

C6H14

question

isopropanol chemical formula

answer

C3H8O

question

silicon dioxide chemical formula

answer

SiO2

question

potassium permanganate chemical formula

answer

KMnO4

question

what is elute of part 1

answer

(isopropanol/water 6:1)

question

what is elute part 2

answer

hexane/ethyl acetate (1:1)

question

Why do you add ethanol to the spinach leaves only to extract the ethanol after mixing

answer

because the compounds we are interested in are relatively nonpolar, by adding ethanol we isolate the compounds we want while removing the polar compounds because thanol is polar

question

why do we use hexane/ethyl acetate as a developing fluid?

answer

because it is nonpolar enough to latch onto the compounds and draw them up the page in the mobile phase but not too nonpolar as to latch on to hardly to the compounds and not allow them to enter the stationary phase

question

two phases in chromatography

answer

mobile phase; stationary phase

question

why do we use silicon dioxide in the plate?

answer

because it will latch onto the polar compounds of the molecules nad cause the more polar molecules to move through the plate slower than the less polar ones.

question

liquids with bp below ____ or solids that ____ may vaporize before the plate is visulized

answer

160; sublime

question

what compounds are we eluting in part 1

answer

sudan IV; bismark brown; fast green; rhodamine

Thin Layer Chromatography

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