Thin Layer Chromatography

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____ a method of separating mixtures into their pure components
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Chromatography
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chromatography: a method of _____
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separating mixtures into their pure component
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Chromatography separates mixtures because the ____ between the various components of the mixture and the stationary phase are different
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intermolecular attractions
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Chromatography separates mixtures because the intermolecular interactions between the ____
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various components of the mixture and the stationary phase are different
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Chromatography is a method of separation using a ___ and a ____
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stationary phase; mobile phase
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separation occurs as the mobile phase ____ the stationary phase
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passes over
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the mobile phase can be ___ or ___
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liquid; gas
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the stationary phase can be ___ or ___
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solid; liquid
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Chromatography-Basic Principle: same basic principle as TLC but now ____ of pressure (_____) to ___ compounds
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use gravity; medium to high; elute
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Chromatography is both a ____ and ____ method
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qualitative; quantitative
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Chromatography is used for _____ the course of a reaction
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monitoring
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Chromatography is used for monitoring ____
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the course of a reaction
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3 types of chromatography used for monitoring the course of a reaction
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thin layer chromatography; gas chromatography; high performance liquid chromatography
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what does TLC stand for
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thin layer chromatography
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what does GC stand for
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gas chromatography
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what does HPLC stand for
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high performance liquid chromatography
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chromatography is used for _____ the components of a reaction
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isolating
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what methods of chromatography are used for isolating the components of a reaction
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column chromatography; prep HPLC; Prep TLC
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Chromatography is both a qualitative and quantitative method used for ___, ___ and ___
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1) monitoring the course of a reaction 2) isolating the components of a reaction 3) assisting in the identification of a compound
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In liquid chromotagraphy ____ is established
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equilibrium
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equation for chemical equilibrium is established and can be represented by the following equation
equation for chemical equilibrium is established and can be represented by the following equation
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in the equation for chemical equilibrium what does Xm and Xs stand for
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the concentrations of solute molecules in the mobile phase and the stationary phase
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in the equation for chemical equilibrium what does Sm and Ss stand for
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Sm and Ss are for the solvent molecule concentrations
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in the equation for chemical equilibrium what does the value K represent
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the distribution coefficient or equilibrium between the solute and solvent molecules and between the mobile and stationary phases
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____ values of K will mean a greater capacity to separate
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high
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Interaction at SiO2/Solvent interface: competition exists between _____ and _____ for sites on the _____
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polar solvent molecules; polar solute molecules; SiO2 surface
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Fill in blank on back elute
Fill in blank on back                      elute
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A mixture of A, B, and C ready to ___ through a column
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in tlc ______ contains material to be separated
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moving phase
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Separation occurs as ____ passes over the ____. This separation occurs when molecules _____ of the ____ through weak intermolecular forces
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moving phase; stationary phase; adhere to the surface; absorbant
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in moving phase the separation occurs when moleculars adhere to the surface of the absorbant through weak intermolecular forces. These forces are ____ and therefore ____
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weak; reversible
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The eluents can be collected at the _____ as ___
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end of the column; individual fractions (cuts)
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Order of elution: ____ are strongly retained on the ____ and therefore eluted late from the chromatographic columns filled with polar stationary phase
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polar compounds; polar stationary phases
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Order of Elution: polar compounds are strongly retained on the polar stationary phase and therefore are ____ from the ___ filled with ____
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eluted; chromatographic columns; polar stationary phase
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Order of Elution: _____ are strongly retained on _____ and therefore are eluted late from the chromatographic column filled with nonpolar (so called ___) phase
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nonpolar compounds; nonpolar stationary phases; reversed
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nonpolar compounds are strongly retained on nonpolar stationary phases and therefore eluted late from the chromatographic column filled with _____
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nonpolar (so called reversed) phase
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Draw column chromatography where A is more polar than B.
Draw column chromatography where A is more polar than B.
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Draw thin layer chromatography where A is more polar than B
Draw thin layer chromatography where A is more polar than B
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(Mobil phase moves upwards)
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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 ____)
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A; stay at the origin of the thin layer chromatography plate; Rf
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what does Rf stand for
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retention factor
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if something has a higher retention factor then in mobile phase it sill ___
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not move as far
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If the solvent moved 100mm and A moved 60mm what is the retention factor
If the solvent moved 100mm and A moved 60mm what is the retention factor
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How do you make a capillary pipet
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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
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See back page for question? 1st: not polar enough 2nd: satisfactory 3rd: too polar
See back page for question?                      1st: not polar enough  2nd: satisfactory  3rd: too polar
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Which of these solvents is satisfactory?
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See next page for question Rf(compound 1)=22/65=0.34 Rf(compound 2)=50/65=0.77
See next page for question                      Rf(compound 1)=22/65=0.34  Rf(compound 2)=50/65=0.77
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What is Rf compound 1? What is Rf compound 2?
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_____ spots are colored
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visualized
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colorless spots require
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I2 vapor; various oxidizing stains such as KMnO4, MoO3, fluorescent indicator in stationary phase (visualized with UV light), special spray reagents
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What does it mean when Rf=1
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spots travel with solvent front
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Rf=0 what does it mean
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spot doesn’t move off baseline, undesirable
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range of Rf values
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Rf from 0 to 1
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what is Rf if spot travels with solvent front
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1
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what is Rf if spot doesn’t move off baseline
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How to use chromatography to test for purity?
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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
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How can we use chromatography to test for identity?
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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
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The stationary phase is coated on ___
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glass or plastic plate
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The mobile phase flows up the plate by ____
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capillary action
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The ____ flows up the plate by capillary action
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mobile phase
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Binder: ______ is used to help stationary phase stick to plastic or glass surface
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hydrogen calcium sulfate
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Normal phase system: the stationary phase is often ____ or ___
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alumina; silica gel
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in a normal phase system the mobile phase is often ___
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organic solvent
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in a normal phase system the separation mechanism is ___
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adsorption
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4 characteristics of TLC
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1) rapid 2) simple 3) requires little sample 4) usually an analytical tool
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a preparative TLC is not good for ____
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separating large (gram) quantities
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3 uses of TLC
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1) purity indicator 2) identification 3) monitoring reactions
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Why do A, B and C separation
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1) chemical nature of A, B, C 2) type of stationary phase 3) mobile phase polarity
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Different types of chemical nature of A, B, and C which affect separation of compounds.
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1) bond-dipoles and polarity 2) hydrogen bonding 3) presence of acidic hydrogens 4) ionic bonds or salts 5) proportion of \”polarity\” to \”grease\”
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What is adsorption?
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It is a surface phenomenon. Molecules ‘stick’ to the surface of a polar solid. \”They are said to be absorbed on the surface.\”
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adsorption is not the same as ___
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absorption
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Adsorption Chromatography: stationary phase is a ____
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solid absorbent
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3 things which may be used as a solid absorbent
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Silica gel (SiO); C18; Alumina (Al2O3)
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In normal phase chromatography the ___ compound moves faster because ____
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least polar; it interacts with the stationary phase to a lesser extent
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Normal Phase Chromatography: the least polar compound has a ____ retention time and therefore travels ____ the plate. It has a ___ Rf
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shorter; farther up; high
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___ and ___ are common polar stationary phases that will interact strongly via electrostatic interactions with molecules that are ____
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SiO2; Al2O3; polar
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____ is kinda like the opposite of normal-phase chromatography
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reverse-phase chromatography
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In reverse-phase chromatogrpahy ____ interacts strongly with greasy compounds containing lots of saturated and unsaturated _____
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C18 backbone; hydrocarbon functionalities
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R(CH2)nCh3 and other hydrocarbon groups are very ____ functional groups and thus stick to the _____ ,resulting in a ___Rf in reverse phase chromatography
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nonpolar; nonpolar stationary phase; Rf
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In reverse phase chromatography the ____ moves faster, has a____ retention time, travels ___ and has a___ Rf
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polar compound; shorter; farther; higher
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adsorption works because of ____
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electrostatic attraction
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partitioning applies to ___ and ____ chromatography
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liquid-liquid; gas-liquid
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____ applies to liquid-liquid and gas-liquid chromatography
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partitioning
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in ____ compounds distribute between the two immiscible liquid phases
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paritioning
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Solubility differences cause ___
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separation
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_____ cause separation
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solubility separation
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The value ___represents the distribution coefficient or equilibrium of a solute A between the ____
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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
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bond dipoles depend on ___, ___ and ___
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bond length; charge separation; electronegativity difference
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a molecular dipole moment is the ____
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vector sum of the bond dipole moments
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____ 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)
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polarizable groups
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polarizable groups are _____ with electron pairs, or filled ____ of double bonds. _____ can be distorted by a dipole in another molecule (____)
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heteroatoms; pi-orbitals; Distribution; stationary phase
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hydrogen bonding may cause a ____
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strong interaction w/ a stationary phase
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in order to have hydrogen bonding an organic molecule must have ____ or ___
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N-H; O-H
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the presence of an ___ hydrogen (_____) contributes to making the molecule polar?
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acidic; low pKa
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different classifications of chromatography by nature of 2 phases
different classifications of chromatography by nature of 2 phases
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2 procedure types of column chromatography
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gravity; flash
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3 physical processes for separation
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adsorption; partitioning; ion exchange
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_____ 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
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HPLC
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How does a developing chamber work
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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)
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Why do you use a pencil instead of a pen when drawing the line
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b/c if you use pen the ink will spread upwards with the solvent
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What do you use in order to transfer die onto plate
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you use a capillary tube (which makes a small dot)
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photosynthetic pigments contained in spinach leaves belong to two classes ____ and ____
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cartenoids; chlorophylls
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2 types of cartenoids
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cartene; xanthophylls
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2 types of chlorophylls in experiment
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cchlorophyll a and b
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_____ is the primary pigment that transforms the energy of sunlight into chemical energy oters are ____
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chlorophyll a; accessory pigments
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what do accessory pigments do
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help efficiently harvest the light and deliver protons to chlorophyll a
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_____ via a redox reaction donates an electron into an electron transport chain
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accessory pigments
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____ is chlorophyll lacking the central magnesium ion and serves as a primary electron acceptor and helps initiate the ETC in photosynthesis
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phenophytin
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pheophytin is ____ lacking the _____. It serves as a primary electron acceptor and helps to ___ in photosynthesis
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chlorophyll; magnesium ion; initiate the electron transport chain
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Chlorophyll a has a ____ where chlorophyll b has an ____
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methyl group; aldehyde functional group
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chlorophyll ___ is slightly more polar than chlorophyll __
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b; a
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____ is a hydrocarbon and is therefore very lipophilic and nonpolar
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beta-Carotene
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what is your solvent front?
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pretty much how high up the solvent trveled up the paper
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what might change Rf of same compound
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type of solvent u use; temperature
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when does stationary phase occur for substance
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when it is stuck to paper nd not moving
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when does mobile phase occur for a substance
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when it is free moving, not stuck to paper
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molecules are constantally moving back and forth between free and absorbed stages. What effects this equilibrium
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1) polarity and size of moleculle 2) polarity of the stationary phase 3) polarity of the solvent
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list following from eluted first to last chlorophyll b, chlorophyll a, beta carotene, violaxanthan, zeaxanthin, lutein
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beta carotene; chlorophyll a; chlorophyll b; lutein; zeaxanthin; violaxanthan
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ethanol chemical formula
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CH3Ch2OH
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ethyl acetate chemical formula
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C4H8O2
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hexane chemical formula
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C6H14
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isopropanol chemical formula
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C3H8O
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silicon dioxide chemical formula
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SiO2
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potassium permanganate chemical formula
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KMnO4
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what is elute of part 1
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(isopropanol/water 6:1)
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what is elute part 2
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hexane/ethyl acetate (1:1)
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Why do you add ethanol to the spinach leaves only to extract the ethanol after mixing
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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
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why do we use hexane/ethyl acetate as a developing fluid?
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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
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two phases in chromatography
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mobile phase; stationary phase
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why do we use silicon dioxide in the plate?
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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.
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liquids with bp below ____ or solids that ____ may vaporize before the plate is visulized
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160; sublime
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what compounds are we eluting in part 1
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sudan IV; bismark brown; fast green; rhodamine

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