CHEM 241 Lab Final
What was the purpose of adding salt to the 5% ethanol in 1. It maximized the amount of ethanol extracted by the pentanol
water solution that was extracted with pentanol in GC EXP 2. It assured that the extraction process is reproducible every time
1 part 1? (2)
To solve for K, what equation was used? K = [EtOH]org/[EtOH]aq or x/.05
What datastudio function was used to correct baseline CALCULATOR
measurements in Experiment 1?
What were the goals of part 2 of experiment 1? (GC) to extract ethanol from three different beer samples (Busch, Busch Light, and Busch
Non-Alcoholic)
to analyze each sample with gas chromatography and use the method of standard
additions to determine the percent ethanol in each of the three samples
Which of the two methods (standard additions or standard the standard calibration plot requires knowledge of the partition coefficient K or the
calibration) requires knowledge of the partition coefficient, fraction of ethanol left behind
K, or the fraction of ethanol left behind in the aqueous
layer?
What were the six ethanol solutions prepared in part 2 of Bev A + 0% ethanol
experiment 1? Bev A + 2% ethanol
Bev A + 4% ethanol
Bev A + 6% ethanol
Bev B + 0% ethanol
Bev C + 0% ethanol
The syringe was rinsed with ________ between each 100% pentanol
injection
What was the standard addition plot? Ethanol Peak Area vs. % ethanol added to Beverage A
The slope of the line for this plot provided the ratio of ethanol peak area/% ethanol added
what?
How was the ethanol content for each beverage by dividing the y-intercept by the slope of the line
determined?
What was cleanup for experiment 1? all solutions were put in liquid waste container
What three characteristics of 1-pentanol make it an 1. it's immiscile with water/beer because it's an organic solution
appropriate choice for use as the extraction solvent in 2. because it's a longer carbon chain with a higher molecular weight, it has a higher
Experiment 1? boiling point than ethanol and so eluted later than ethanol--giving good distinction
between peaks
3. ethanol is more soluble in pentanol than water because of the similar molecular
interactions between the two alcohols
Why would there be more than two peaks in glassware was cleaned with distilled water prior to the beginning of the experiment--
chromatograms that analyzed only ethanol in pentanol this could be a water peak
solutions (week 1)?
, CHEM 241 Lab Final
How would this hypothesis be confirmed? analyze a water sample using GC set to the same experimental parameters--a peak
at the same Tr would confirm that it was water contamination in the ethanol-
pentanol solutions
Why was knowledge of the partition coefficient, K, not because the plot was constructed from solutions that had already been extracted,
necessary for the standard additions method? so K was inherently included in the plot and best-fit line.
Could the calibration plot from week 1 have been used to No because of different experimental paramaters, GC settings, experimental
determine the actual concentrations of alcohol in the instruments, etc. Additionally, the partition coefficient between water and pentanol
beverage samples analyzed during week 2? might be slightly different than the partition coefficient between water and beer
(since beer is a complex mixture containing many other compounds that can affect
solubility)
What would have happened if this experiment had been the stationary phase would have been a solid rather than a liquid, the solubility of
carried out using gas-solid chromatography? the analyte in a solid would likely have been very different (if it could be soluble in a
solid at all), changing the observed elution patterns
What was the protein analyzed in Experiment 2? bovine serum albumin
What is electrophoresis based on? the idea that charged molecules move (migrate) in an electric field
what format of electrophoresis was used in experiment 2? slab electrophoresis
What was the slab? polyacetate (cellulose)
The ends of the paper were in... aqueous buffer reservoirs on each side
The aqueous buffer had what function? connecting the two buffer reservoirs electrically
E= Electric Field (E) = Voltage (V) / distance between two electrodes (d)
Where is the sample placed? a spot of line across the center of the strip called the sample origin
A proteins direction of migration is determined by its net charge; pH
___________ at a given _________.
Positively charged proteins migrate toward the cathode; anode
___________ while negatively charged proteins migrate
toward the __________.
The direction of migration is simply goverened by the electrostatic attraction
________ between charged molecules and the charged
electrodes.
, CHEM 241 Lab Final
What is Uep? the rate at which the charged molecule migrates
Uep= magnitude of the electric field (E) * uep (electrophoretic mobility)
uep = (q/f)*E
What is q? molecule's total charge
What is f and what does it depend on? (3) frictional coefficient--
1. shape of molecule
2. hydrodynamic radius of molecule
3. viscosity of fluid containing molecule
Give two applications of gel electrophoresis: 1. determination of net molecular charge
2. separation of charged molecules
What is the isoelectric point of a molecule? the pH value that leads to electrical neutrality , and there fore no observed migration
What was the plot constructed in this experiment? Average distance migrated vs. pH
The degree to which an acid dissociates depends on: the pH
acid dissociation constants
What is the equation for the pI (isoelectric point)? pI = pKa1 + pKa2 /2
What kind of stain was used to make the proteins appear? Ponceau stain
What corrosive, dangerous chemical is in Ponceau stain? trichloroacetic acid
What solution were the strips placed into after staining with 5% acetic acid (stain binds the protein and wills stay on the protein, but the acetic
Ponceau stain? acid removes all the other stain)
Then where were the strips placed? They were placed into distilled water to rinse away any remaining stain and acetic
acid.
A positive sign was given to distances toward the cathode; anode
____________. A negative sign was given to distances
toward the __________.
What was the purpose of adding salt to the 5% ethanol in 1. It maximized the amount of ethanol extracted by the pentanol
water solution that was extracted with pentanol in GC EXP 2. It assured that the extraction process is reproducible every time
1 part 1? (2)
To solve for K, what equation was used? K = [EtOH]org/[EtOH]aq or x/.05
What datastudio function was used to correct baseline CALCULATOR
measurements in Experiment 1?
What were the goals of part 2 of experiment 1? (GC) to extract ethanol from three different beer samples (Busch, Busch Light, and Busch
Non-Alcoholic)
to analyze each sample with gas chromatography and use the method of standard
additions to determine the percent ethanol in each of the three samples
Which of the two methods (standard additions or standard the standard calibration plot requires knowledge of the partition coefficient K or the
calibration) requires knowledge of the partition coefficient, fraction of ethanol left behind
K, or the fraction of ethanol left behind in the aqueous
layer?
What were the six ethanol solutions prepared in part 2 of Bev A + 0% ethanol
experiment 1? Bev A + 2% ethanol
Bev A + 4% ethanol
Bev A + 6% ethanol
Bev B + 0% ethanol
Bev C + 0% ethanol
The syringe was rinsed with ________ between each 100% pentanol
injection
What was the standard addition plot? Ethanol Peak Area vs. % ethanol added to Beverage A
The slope of the line for this plot provided the ratio of ethanol peak area/% ethanol added
what?
How was the ethanol content for each beverage by dividing the y-intercept by the slope of the line
determined?
What was cleanup for experiment 1? all solutions were put in liquid waste container
What three characteristics of 1-pentanol make it an 1. it's immiscile with water/beer because it's an organic solution
appropriate choice for use as the extraction solvent in 2. because it's a longer carbon chain with a higher molecular weight, it has a higher
Experiment 1? boiling point than ethanol and so eluted later than ethanol--giving good distinction
between peaks
3. ethanol is more soluble in pentanol than water because of the similar molecular
interactions between the two alcohols
Why would there be more than two peaks in glassware was cleaned with distilled water prior to the beginning of the experiment--
chromatograms that analyzed only ethanol in pentanol this could be a water peak
solutions (week 1)?
, CHEM 241 Lab Final
How would this hypothesis be confirmed? analyze a water sample using GC set to the same experimental parameters--a peak
at the same Tr would confirm that it was water contamination in the ethanol-
pentanol solutions
Why was knowledge of the partition coefficient, K, not because the plot was constructed from solutions that had already been extracted,
necessary for the standard additions method? so K was inherently included in the plot and best-fit line.
Could the calibration plot from week 1 have been used to No because of different experimental paramaters, GC settings, experimental
determine the actual concentrations of alcohol in the instruments, etc. Additionally, the partition coefficient between water and pentanol
beverage samples analyzed during week 2? might be slightly different than the partition coefficient between water and beer
(since beer is a complex mixture containing many other compounds that can affect
solubility)
What would have happened if this experiment had been the stationary phase would have been a solid rather than a liquid, the solubility of
carried out using gas-solid chromatography? the analyte in a solid would likely have been very different (if it could be soluble in a
solid at all), changing the observed elution patterns
What was the protein analyzed in Experiment 2? bovine serum albumin
What is electrophoresis based on? the idea that charged molecules move (migrate) in an electric field
what format of electrophoresis was used in experiment 2? slab electrophoresis
What was the slab? polyacetate (cellulose)
The ends of the paper were in... aqueous buffer reservoirs on each side
The aqueous buffer had what function? connecting the two buffer reservoirs electrically
E= Electric Field (E) = Voltage (V) / distance between two electrodes (d)
Where is the sample placed? a spot of line across the center of the strip called the sample origin
A proteins direction of migration is determined by its net charge; pH
___________ at a given _________.
Positively charged proteins migrate toward the cathode; anode
___________ while negatively charged proteins migrate
toward the __________.
The direction of migration is simply goverened by the electrostatic attraction
________ between charged molecules and the charged
electrodes.
, CHEM 241 Lab Final
What is Uep? the rate at which the charged molecule migrates
Uep= magnitude of the electric field (E) * uep (electrophoretic mobility)
uep = (q/f)*E
What is q? molecule's total charge
What is f and what does it depend on? (3) frictional coefficient--
1. shape of molecule
2. hydrodynamic radius of molecule
3. viscosity of fluid containing molecule
Give two applications of gel electrophoresis: 1. determination of net molecular charge
2. separation of charged molecules
What is the isoelectric point of a molecule? the pH value that leads to electrical neutrality , and there fore no observed migration
What was the plot constructed in this experiment? Average distance migrated vs. pH
The degree to which an acid dissociates depends on: the pH
acid dissociation constants
What is the equation for the pI (isoelectric point)? pI = pKa1 + pKa2 /2
What kind of stain was used to make the proteins appear? Ponceau stain
What corrosive, dangerous chemical is in Ponceau stain? trichloroacetic acid
What solution were the strips placed into after staining with 5% acetic acid (stain binds the protein and wills stay on the protein, but the acetic
Ponceau stain? acid removes all the other stain)
Then where were the strips placed? They were placed into distilled water to rinse away any remaining stain and acetic
acid.
A positive sign was given to distances toward the cathode; anode
____________. A negative sign was given to distances
toward the __________.
