CHEM 241L Final Exam Questions With
Accurate Answers
Safety Protocol - ANSWER safety goggles
lab coat
clothing that covers shoulders to ankles
footwear that covers entire foot
Gloves worn when handling glass and chemicals
don't wear gloves outside of lab room
tie back hair
Late policy - ANSWER After 48 hours - no longer accepted
0-24 hours - 10% penalty
24-48 hours - 20% penalty
Excused absence policy - ANSWER Missing two or more experiments will
automatically result in an F.
Absences are evaluated on a case-by-case basis.
If you are sick, you must have a note from campus health.
Fill out the survey for an excused absence request.
Decisions will be emailed within 48 hours by Nevins.
Lab makeup policy - ANSWER Option 1: attend another section of lab so long as
that lab is doing the experiment you missed and has ample space (22 students
only)
Option 2: Make up the lab from 1:25 - 4:15 pm on the Friday of the week after the
missed lab.
Lab report extension policy - ANSWER Fill out the lab report extension form
EXP 1: What technique is used to separate our mixture? - ANSWER Solvent-
solvent extraction
Gas-liquid chromatography
EXP 1: Was is our complex mixture for day 2? - ANSWER Busch Beer
Non-alcoholic
Light
Regular
EXP 1: What is a partition coefficient, and how is it calculated? - ANSWER
Partition coefficient = K
,The higher the partition coefficient, the better the solvent extracts the analyte
from the sample matrix
K = [S]org/[S]aq
EXP 1: How do you use a three-valve bulb? - ANSWER top nozzle: valve to expel
air from bulb
middle nozzle: valve to suction soln into pipet
size nozzle: valve to drain soln out of pipet
EXP 1: Why was a solvent-solvent extraction necessary? - ANSWER Pentanol
(organic solvent) used to extract ethanol from sample matrix - we only wanted to
examine ethanol
EXP 1: What was used as the organic layer of our extract? - ANSWER Pentanol
EXP 1: What is the MP? - ANSWER GAS (vaporized extraction sample)
EXP 1: What is the SP? - ANSWER LIQUID
Molecules with a higher BP will spend a longer amount of time in the stationary
phase and therefore in the column.
What type of column? - ANSWER Packed
EXP 1: What determines the order of elution with our experimental setup? -
ANSWER POLARITY
Non-polar molecules (such as alkanes) cannot strongly interact with the
stationary phase and thus elute from the column more quickly than polar
compounds.
EXP 1: What is a standard calibration curve? - ANSWER -% etOH (x axis)
-Average etOH peak area (y axis)
-Using prepared standard solns of 2, 4, and 6% etOH
-You use this calibration plot to determine the amount of etOH extracted when 1
mL pentanol is added to 1 mL of a 5% etOH in H2O soln.
EXP 1: What is a standard addition curve? - ANSWER - % etOH added to
Beverage A (x axis)
- etOH peak area (y axis)
EXP 1: How is a standard addition curve different from a standard calibration
curve? - ANSWER Standard addition is different from calibration in that you will
directly calculate the amount of analyte in the original sample
One advantage of the standard addition method over the calibration method is
that t does not require you to have any knowledge of either the partition
coefficient (K) or the fraction left behind.
, Neither methods require that all etOH be extracted.
EXP 1: Calculate the % etOH using a calibration curve - ANSWER
EXP 1: Calculate the % etOH using a standard addition curve - ANSWER
EXP 1: What is the detector? - ANSWER thermal conductivity detector
- measures the differences in thermal conductivities between the carrier gas
and the gaseous sample components
EXP 2: What protein was analyzed in this experiment? - ANSWER Bovine serum
albumin
EXP 2: What were the strips used in this experiment? - ANSWER Cellulose
polyacetate strip
EXP 2: What electrophoretic technique is used? - ANSWER Slab electrophoresis
EXP 2: What is a cathode; what is an anode? - ANSWER Cathode: negative end
Anode: positive end
EXP 2: How would ion concentration charge and size effect migration? -
ANSWER Charge:
- positive ions move toward the cathode
- negative ions move toward the anode
- as molecular charge increases, mobility will increase
- if a molecule has 0 charge - will not move
Size:
Smaller molecules migrate faster than larger molecules
EXP 2: Why did pH effect migration? - ANSWER It affects the protonation of BSA.
- When at higher pHs, BSA became more protonated and traveled toward the
cathode
- When at lower pHs, BSA became more deprotonated and traveled toward the
anode
EXP 2: What is the isoelectric point, how is this calculated? - ANSWER pH at
which a molecule is electrically neutral.
pI = (pKa1 + pKa2)/2
EXP 2: What were the power supply settings? - ANSWER 300 V
3 mA/strip (two trays [cathode and anode] with 4 strips -- 8 x 3 = 24 mA needed)
Time: 45 min
EXP 2: What stain was used in this experiment? - ANSWER Ponceau stain
Accurate Answers
Safety Protocol - ANSWER safety goggles
lab coat
clothing that covers shoulders to ankles
footwear that covers entire foot
Gloves worn when handling glass and chemicals
don't wear gloves outside of lab room
tie back hair
Late policy - ANSWER After 48 hours - no longer accepted
0-24 hours - 10% penalty
24-48 hours - 20% penalty
Excused absence policy - ANSWER Missing two or more experiments will
automatically result in an F.
Absences are evaluated on a case-by-case basis.
If you are sick, you must have a note from campus health.
Fill out the survey for an excused absence request.
Decisions will be emailed within 48 hours by Nevins.
Lab makeup policy - ANSWER Option 1: attend another section of lab so long as
that lab is doing the experiment you missed and has ample space (22 students
only)
Option 2: Make up the lab from 1:25 - 4:15 pm on the Friday of the week after the
missed lab.
Lab report extension policy - ANSWER Fill out the lab report extension form
EXP 1: What technique is used to separate our mixture? - ANSWER Solvent-
solvent extraction
Gas-liquid chromatography
EXP 1: Was is our complex mixture for day 2? - ANSWER Busch Beer
Non-alcoholic
Light
Regular
EXP 1: What is a partition coefficient, and how is it calculated? - ANSWER
Partition coefficient = K
,The higher the partition coefficient, the better the solvent extracts the analyte
from the sample matrix
K = [S]org/[S]aq
EXP 1: How do you use a three-valve bulb? - ANSWER top nozzle: valve to expel
air from bulb
middle nozzle: valve to suction soln into pipet
size nozzle: valve to drain soln out of pipet
EXP 1: Why was a solvent-solvent extraction necessary? - ANSWER Pentanol
(organic solvent) used to extract ethanol from sample matrix - we only wanted to
examine ethanol
EXP 1: What was used as the organic layer of our extract? - ANSWER Pentanol
EXP 1: What is the MP? - ANSWER GAS (vaporized extraction sample)
EXP 1: What is the SP? - ANSWER LIQUID
Molecules with a higher BP will spend a longer amount of time in the stationary
phase and therefore in the column.
What type of column? - ANSWER Packed
EXP 1: What determines the order of elution with our experimental setup? -
ANSWER POLARITY
Non-polar molecules (such as alkanes) cannot strongly interact with the
stationary phase and thus elute from the column more quickly than polar
compounds.
EXP 1: What is a standard calibration curve? - ANSWER -% etOH (x axis)
-Average etOH peak area (y axis)
-Using prepared standard solns of 2, 4, and 6% etOH
-You use this calibration plot to determine the amount of etOH extracted when 1
mL pentanol is added to 1 mL of a 5% etOH in H2O soln.
EXP 1: What is a standard addition curve? - ANSWER - % etOH added to
Beverage A (x axis)
- etOH peak area (y axis)
EXP 1: How is a standard addition curve different from a standard calibration
curve? - ANSWER Standard addition is different from calibration in that you will
directly calculate the amount of analyte in the original sample
One advantage of the standard addition method over the calibration method is
that t does not require you to have any knowledge of either the partition
coefficient (K) or the fraction left behind.
, Neither methods require that all etOH be extracted.
EXP 1: Calculate the % etOH using a calibration curve - ANSWER
EXP 1: Calculate the % etOH using a standard addition curve - ANSWER
EXP 1: What is the detector? - ANSWER thermal conductivity detector
- measures the differences in thermal conductivities between the carrier gas
and the gaseous sample components
EXP 2: What protein was analyzed in this experiment? - ANSWER Bovine serum
albumin
EXP 2: What were the strips used in this experiment? - ANSWER Cellulose
polyacetate strip
EXP 2: What electrophoretic technique is used? - ANSWER Slab electrophoresis
EXP 2: What is a cathode; what is an anode? - ANSWER Cathode: negative end
Anode: positive end
EXP 2: How would ion concentration charge and size effect migration? -
ANSWER Charge:
- positive ions move toward the cathode
- negative ions move toward the anode
- as molecular charge increases, mobility will increase
- if a molecule has 0 charge - will not move
Size:
Smaller molecules migrate faster than larger molecules
EXP 2: Why did pH effect migration? - ANSWER It affects the protonation of BSA.
- When at higher pHs, BSA became more protonated and traveled toward the
cathode
- When at lower pHs, BSA became more deprotonated and traveled toward the
anode
EXP 2: What is the isoelectric point, how is this calculated? - ANSWER pH at
which a molecule is electrically neutral.
pI = (pKa1 + pKa2)/2
EXP 2: What were the power supply settings? - ANSWER 300 V
3 mA/strip (two trays [cathode and anode] with 4 strips -- 8 x 3 = 24 mA needed)
Time: 45 min
EXP 2: What stain was used in this experiment? - ANSWER Ponceau stain
