Chem 241L

Using the image of a 3-way pipette valve below, please match the letters A, S and E to the description that matches their proper use. A. Valve used to draw liquid into the pipet B. Valve used to drain the solution out of the pipet C. Valve used to expel air from the bulb 1. E 2. A 3. S

1. B 2. C 3. A

5. The G-75 stationary phase has a fractionation range of 3,000 - 80,000. A solution containing 4 proteins (each MW is listed below) is introduced to the top of this column and allowed to pass through to separate the proteins. Protein A: 6,000 Da Protein B: 2,000 Da Protein C: 60,000 Da Protein D: 29,000 Da Given the above proteins, what is the correct elution order (from 1st to last) that would be observed? A. Second B. Third C. Fourth D. First 1. Protein C 2. Protein D 3. Protein A 4. Protein B

1. C 2. D 3. A 4. B

4. You add 100 mL of 0.10 M HCl to 100 mL of 0.50 M phosphate (H2PO4-; pKa = 2.148). What is the pH of this solution? pH =

1.55

Calculate the concentration of a sample with an absorbance of 0.57, a molar absorptivity of 76 and the cuvette path length of 0.50 cm

15 mM

3. If the Ka of a weak acid is 7.2 x 10-3, what is the pKa? pKa =

2.14

5. What is the retention volume if the void volume is 13mL, Vi = 7 mL and the partition coefficient is 3.2? Vr =

35.4 mL

2. Calculate the isoelectric point for Protein B, which has two ionizable protons (pKa1 = 3.5 and pKa2 = 7.5). pI =

5.5

1. At the end of lab, what do you do with the glass vials, lids and lid inserts? A. Empty your solutions into the waste container, clean the vials, lids and liners and place in the hood in front of the lab room. B. Leave the solutions in the vials, capped, and place in the lab hood for the prep staff to dispose of. C. Empty your solutions into the waste container, place the vials in the glass waste container and throw away the lids and lid liners. D. Empty your solutions into the waste container, clean the vials, lids and liners and place in your lab drawer. E. Empty your solutions into the waste container, clean the vials and lids, placing these in the hood in front of the lab room, and throw away the lid liners in the solid waste container.

A

4. What is the acceptable range of pKas that you can use to make a buffer of a certain pH? A. ± 1 B. between 2.1 and 2.5 C. 0 to 14 D. ± 2

A

6. The partition coefficient is mathmatically described as: A. K = [C]2/[C]1 B. K = [C]1 * [C]2 C. K = [C]1/[C]2 D. K = [C]2 - [C]1

A

You put a flask containing a solution of benzoic acid and organic solvent on a hot plate at a medium setting in order to evaporate off the organic solvent. Your TA has told you it will take 15 min. After 5 min you realize you have to use the restroom. You should do which of the following? A. Ask your TA to watch your experiment so you can go to the restroom. B. Place a watch glass on top of the flask and then quickly go to the restroom. C. Since you have 10 minutes until the solvent completely evaporates, you may quickly go to the restroom. D. Turn the hot plate to LOW and then go to the restroom.

A

1. You are instructed to make a 2% ethanol in pentanol solution using a 10 mL volumetric flask. What are the correct steps to take (select all correct steps - NOTE the steps are not necessarily listed in the correct order) A. After adding the ethanol to the 10 mL flask, add a small amount of pentanol to the flask and swirl to mix the solution. Then add pentanol to fill up to the mark. B. Measure out 0.2 mL of ethanol and add to the 10 mL volumetric flask. C. After adding the ethanol to the 10 mL flask, fill the flask with pentanol to the mark. D. Measure out 9.8 mL of pentanol and add to the 10 mL volumetric flask

A, B

4. Which combination(s) of equal volumes of the below reactants would result in the formation of a buffer? (select all that form a buffer) 1. 0.1 M CH3COOH and 0.05 M CH3COO- 2. 0.1 M CH3COOH and 0.05 M NaOH 3. 0.1 M CH3COO- and 0.05 M HCl 4. 0.1 M NaOH and 0.1 M HCl A. 3 B. 1 C. 2 D. 4

A, B, C

What are things that you should check when disposing of chemical waste (select all that apply) A. Be sure to open the funnel on the liquid waste or the lid on the solid waste bucket before disposing of your chemicals. B. For liquid waste, ensure the level of liquid is below the top of the bottle. C. Be sure that the lid of the waste container is completely closed, even if you know you will be returning to dispose of additional chemicals in a minute. D. Leave the lid of the waste container open since you know you will likely use it again in a few minutes.

A, B, C

Which of the following situations should you report to your TA if they occur in lab (select all that apply)? A. You burned your finger on a hot piece of glass B. Even though you were supposed to leave them on, you removed your goggles for a minute at your lab bench and in the process you think you got something in your eye. C. You spill dilute acid on your arm. D. You or someone else in lab feels faint and/or has fainted

A, B, C, D

6. Two common parameters that are often used to describe the efficiency of a separation are ______ and _____. A. resolution B. peak area C. peak intensity D. relative retention E. flow rate

A, D

Proper lab attire is required while in your chemistry lab. Select all that are considered appropriate lab attire. A. Long skirt B. Shorts C. Tank top D. Sneakers E. ballet flats F. Long pants G. Sandles

A, D, F

1. Calculate the partition coefficient if 1/3 of a 10% ethanol sample is extracted from the aqueous phase with 1-pentanol. (Hint: K = [CH3CH2OH]org / [CH3CH2OH]aq) A. 1.0 B. 0.5 C. 0.66 D. 0.33

B

3. Calculate the molar absorptivity of bromothymol blue at 620 nm if the percent transmittance (% T) is determined to be 15.1% at this wavelength. The pathlength of the cuvet is 10.0 mm and the concentration of bromothymol blue solution is 5.00 x 10-5 M. A. 4.10 x 10-5 M-1 cm-1 B. 1.65 x 104 M-1 cm-1 C. 1.41 x 104 M-1 cm-1 D. 3.02 x 104 M-1 cm-1

B

3. Which of the following values indicate the strongest acid? A. pKa = 6.20 B. Ka = 6.32 x 10-2 C. pKa = 4.30 D. Ka = 1.31 x 10-5

B

4. After you finish lab today, you are not sure what to do with the solutions you prepared. What should you do next? A. Pour them down the drain, they are weak acids and/or bases so they are harmless. B. Ask your TA before proceeding. C. None of these answers are correct D. Dump the in the waste container in the hood regardless of what the solutions are made of.

B

5. How is K calculated in a size exclusion chromatography type experiment? A. K = (Vm + V0)/(Vr + V0) B. K = (Vr - V0)/(Vm - V0) C. K =(Vm x V0)/(Vr x V0) D. K = (Vr x V0)/(Vm x V0)

B

5. How will you determine the retention volume for the protein samples in today's experiment? A. Determine the most intense fractions of the two proteins using both a UV-Vis spectrophotemeter and also by analyzing the color intensity of the fractions collected in the test tubes (looking for the most intense fractions). B. Determine the most intense fractions of the two proteins by visually analyzing the color intensity of the fractions collected in the test tubes only, i.e. looking for most intense fractions. C. Determine the most intense fractions for each protein using a UV-Vis spectrophotometer. D. Determine the most intense fractions for one protein with a UV-Vis spectrophotometer and determine one of the others visually by analyzing the color intensity of the fractions from this protein.

B

6. How can you most accurately determine the actual flow rate of the mobile phase through the column? A. Measure the column volume. B. Collect mobile phase from the column in a graduated cylinder for a specified period of time. C. Measure the amount of time it takes for the void peak to elute. D. Read the dial on the pump.

B

6. If a piece of glassware breaks during your experiment, the first thing you should do is: A. Sweep up the broken pieces and dispose of them in the glass waste box. B. Inform the TA and ask for assistance. C. Pick up the broken pieces of glass and dispose of the in the glass waste box. D. Go to Morehead 102 and purchase your replacement glassware.

B

7. When making your absorbance measurements, you must fill the cuvette _____ full with solution. A. 1/2 B. 3/4 C. 1/4 D. to the top

B

If you are unsure about where to dispose of the waste from your experiment. What is the proper procedure you should follow? A. Make a guess and dispose of it based on that guess. B. Ask your TA where you should dispose of the chemical. C. Ask your lab partner where to dispose of the chemical D. All of the above are acceptable.

B

What is the correct way to mix water and acid A. Slowly add water to acid B. Slowly add acid to water C. It does not matter which is added first as long as it is done slowly

B

7. Which sugars are are metabolized most quickly? (Select all that apply) A. Sucrose B. Fructose C. Glucose

B, C

There are many hazards associated with chemicals. Which of the following are the proper procedure to learn about the hazards you may encounter in lab (select all that apply). A. Ask your friend who has taken the lab before. B. Check with your TA if unsure. C. Your lab manual. D. Safety Data Sheet (SDS, for short)

B, C, D

Before injecting samples into the GC column, you were required to check the the settings on the front of the instrument to ensure they were correct. What would have happened if the column temperature would have been set too low? (select all that apply) A. there would be no difference in the chromatogram. B. you would observe an increased separation between the peaks for various components of the mixture. C. the samples would pass through the column more quickly. D. the samples would pass through the column more slowly. E. you would observe a decreased separation between the peaks for various components of the mixture.

B, D

2. In today's lab, you will measure the migration of ___ in 5 different pH buffer solutions.

BSA

1. If a standard addition plot was constructed for a given analysis and the linear regression gave you a slope of 1.5 and a y-intercept of 4, what is the percentage of ethanol in the sample? A. 1.5% B. 4.5% C. 2.67% D. 0.5%

C

1. Which of the following statements pertaining to lab today are correct? (select all that apply) A. Like Week 1 of the GC Experiment, you will prepare 2 %, 4 % and 6 % standard solutions, that you will then use prepare your standard addition standards. B. You will need to run the 2%, 4% and 6% standard solutions again today, before running your standard addition solutions. C. You will be provided with 2 %, 4 %, and 6 % standard solutions that you will use to prepare your standard addition, standard solutions. D. You should bring a beaker of pentanol to the GC room.

C

3. For the extraction performed in this experiment you will use the ________ layer, which is _______. A. top: ethyl acetate B. Bottom: ethyl acetate C. Bottom: water D. top: water

C

5. What do you do with the phosphate buffer in today's lab? A. Pour it into the liquid waste container in the hood. B. Pour it back in the container for re-use. C. Pour it down the sink and rinse down the drain with running water. D. Neutralize with sodium bicarbonate and pour into the liquid waste container.

C

5. Where should you place your backpack when you come to lab? A. There is no designated area for backpacks. B. On the floor next to your lab drawer. C. In the cabinets under the white board labeled for backpack storage. D. On the ledge above your lab bench. E. In your lab drawer.

C

7. How should the Ferrocyanide and Ferricyanide solutions be disposed of? A. Put them in a covered flask for next week's lab B. Neutralize with base, then flush down the sink C. Pour them into the waste bottle in the hood D. Flush them down the sink with plenty of water

C

If there is no chemical waste container in the main lab hood, what should you do? A. Leave your liquid waste in a 400 mL beaker and place it in the main lab hood. B. This must mean that the waste is OK to pour down the drain in the lab room sink. C. You should immediately let your TA know that there is no waste container and always verify with them whether any chemical waste should be poured down the drain. D. You can use the solid waste container since there is no liquid waste container.

C

Where should you place your backpack when you come to lab? A. In your lab drawer. B. On the ledge above your lab bench. C. In the cabinets under the white board labeled for backpack storage. D. There is no designated area for backpacks. E. On the floor next to your lab drawer.

C

Which of the following statements is correct about eating in the lab? A. It is permitted to finish my food at the front of the lab as long as nobody has started working with chemicals. B. There is no specific rule about eating in lab, I can eat at my bench while performing my experiment. C. I am not allowed to eat anything while in the lab room. D. Your TA will let you know if there is an occasion where it is ok to eat in the lab room.

C

1. If you injected a mixture containing heptane (boiling point 98 ˚C), pentane (bp 36 ˚C), hexane (bp 69 ˚C) and octane (126 ˚C) onto a Carbowax 20M column, the compounds would come off in what order (first to last)? Match the order in which each compound will elute from the column. A. Second B. Fourth C. First D. Third 1. Pentane 2. Octane 3. Heptane 4. Hexane

C, B, D, A

When using a volumetric flask to make a solution, which statement(s) represent a correct procedure for making the given solution. (select all that apply) A. When preparing 10 mL of a 2% ethanol in pentanol solution, first add 9.8 mL of pentanol, then add 0.2 mL of ethanol and swirl. B. When making a solution of a weak acid from a solid, first weigh the solid, then add it to the volumetric flask and fill with water so that the bottom of the meniscus is at the line on the neck of the flask. C. When preparing 10 mL of a 2% ethanol in pentanol solution, first 0.2 mL of ethanol, then add a small amount of pentanol to mix. Once mixed, add pentanol until the bottom of the meniscus is at the line on the neck of the volumetric flask. D. When making a solution of a weak acid from a solid, first weigh the solid, then add it to the volumetric flask. Add a small amount of water to first dissolve the solid, then once dissolved, fill the flask the rest of the way with water so that the bottom of the meniscus is at the line on the neck of the flask. E. When preparing 10 mL of a 2% ethanol in pentanol solution, first 0.2 mL of ethanol, then add pentanol until the bottom of the meniscus is at the line on the neck of the volumetric flask.

C, D

3. In this experiment you are trying to determine _____________. A. the partition coefficient of bromothymol blue in a water-ethyl acetate mixture. B. the concentration of bromothymol blue. C. the wavelength at which the acidic and basic forms of bromothymol blue absorb maximally. D. the pKa of bromothymol blue

C,D

2. How will you apply the BSA solution to the electrophoresis strips? A. With a glass Pasteur pipette B. With a small plastic pipette tip. C. With an applicator specially designed for electrophoresis that has two parallel wires with which to apply the solution. D. With an applicator specially designed for electrophoresis that has one wire to apply the solution. E. With a disposable plastic pipette.

C.

2. The isoelectric point is mathematically defined as: A. pH = 1/4 (pKa1 + pKa2) B. pH = 1/2 (pKa1 x pKa2) C. pH = 1/2 (pKa1 + pKa2) D. pH = 2 (pKa1 + pKa2)

C.

2. When the pH of the run buffer is less than the isoelectric pH of a protein, _________. A. It will not migrate any further in the electric field. B. It will have a net negative charge. C. It will have a net positive charge. D. the protein will have an average charge of zero. E. Both A and D

C.

Whats the order of pigments from least to most polar?

Carotenes < Chlorophylls < Xanthrophylls

1. For a solute (S) partitioning between aqueous and organic solvents you can write K = _______. A. ([S]aqueous/[S]organic)n B. ([S]organic/[S]aqueous) x qn C. ([S]aqueous/[S]organic) x qn D. [S]organic/[S]aqueous E. [S]aqueous/[S]organic F. ([S]organic/[S]aqueous)n

D

1. In today's experiment you will make how many injections? A. As many as you can fit in during the lab period. B. 1 C. 2 if you have time, otherwise at least one of each solution. D. 3 if you have time, otherwise at lease two of each solution. E. 4 if you have time, otherwise at least three of each solution.

D

4. Which of the below is the correct Henderson-Hesselbalch equation? A. pH = pKa + Log [HA]/[A-] B. pKa = pH + Log [A-]/[HA] C. pKa = pH - Log [HA]/[A-] D. pH = pKa + Log [A-]/[HA]

D

6. After adding the saturated NaCl solution to the spinach extract in the separatory funnel, you should add more of which of the below to help extract more spinach into the organic phase. A. Acetonitrile B. Ethyl Acetate C. Saturated NaCl solution D. Acetone

D

7. In today's lab, you are indirectly determining the concentration of the following (select all that apply) A. Sucrose B. Fructose C. Lactose D. Glucose

D

7. The spectrophotometric enzyme assay ___________________? A. Involves one enzymatic reaction. B. Is not useful in this experiment. C. Directly determines the amount of glucose in the solution. D. Indirectly determines the amount of glucose in the solution.

D

7. You take 1.0 mL of your unknown solution and dilute it to 50 mL. You then determine that the concentration of this diluted sample is 5.0 M. What was the concentration of the original (undiluted) sample? A. 4.0 x 10^-3 M B. 10.0 M C. 0.10 M D. 250 M

D

If a piece of glassware breaks during your experiment, the first thing you should do is: A. Pick up the broken pieces of glass and dispose of the in the glass waste box. B. Sweep up the broken pieces and dispose of them in the glass waste box. C. Go to Morehead 102 and purchase your replacement glassware. D. Inform the TA and ask for assistance.

D

The eyewash in my lab is located: A. In the hallway B. By the entry door C. At my work station D. At the front sink

D

When measuring out a sample, which item below would give you the highest accuracy. A. a small beaker B. A large beaker C. A graduated cylinder D. a volumetric flask E. an Erlenmeyer flask

D

When obtaining reagents from the main lab hood for your experiment, which of the following indicated the proper technique? A. Obtain the stock bottle from the hood and carefully bring it to your bench. When finished, pass it along to the next student/group. B. It depends on the instructions that your TA provides during the pre-lab lecture. C. Go to the main hood, wait your turn and pipette directly out of the stock bottle. D. Pour a small amount into a beaker or flask, cover and bring it back to your lab bench.

D

When you are finished using a disposable glass Pasteur pipette, where should you dispose of it? A. In the trash can at the end of the lab benches. B. In the solid waste container in the hood. C. Clean it for use in another experiment. D. In the designated glass waste container in the lab room.

D

You accidentally prick your finger with the end of a glass pipette, drawing a tiny drop of blood. What is the correct response? A. Its a minor inury so you ignore it and continue to work on your experiment. B. Get a band-aid for it and continue to work on your experiment. C. Rinse your finger very well (15 minutes) with water, put a band-aid on the injury and continue working. D. Tell your TA immediately so they can fill out an accident report, then rinse your finger very well (15 minutes) with water, and put a band-aid on the injury.

D

1. What is the primary goal of today's experiment? A. To determine the amount of ethanol extracted from the extraction sample. B. To determine an unknown amount of ethanol in your sample. C. To simply observe the separation of components in your sample. D. To determine the partition coefficient of ethanol between water and pentanol.

D.

5. Which compound will elute from the column first, Dextran Blue (2 x 106 Da) or Phenol Red (354.38 g/mol)?

Dextran Blue

3. Why is it important to chose the wavelength of maximum absorption for a spectrophotometric analysis? A. This is the wavelength that will give the maximum response for a given concentration of analyte. B. At this wavelength, there will be minimal variations from any monochrometer shifts because it is a semi-flat region of the spectra. C. The response of the detector will be best at this wavelength because more light will pass through the sample. D. All of the above. E. A and B F. A and C

E

4. In today's lab you will measure the change in pH of each of the prepared buffer solutions by adding which of the following drop-wise? A. 0.10 M HCl Only B. 0.10 M NaOH and 0.10 M HCl C. 0.50 M NaOH and 1.0 M HCl D. 0.10 M NaOH Only E. 1.0 M NaOH and 1.0 M HCl

E

7. You have a solution that you wish to dilute 25 times (25x). Which of the below represents a 25x dilution? A. 50 mL of a solution diluted to 150 mL. B. 50 mL of solution diluted to 100 mL. C. 5 mL of a solution diluted to 100 mL D. 50 mL of a solution diluted to 200 mL. E. 1 mL diluted to 25 mL

E

Which of the following statements lists the correct order in which the light passes through a uv/vis spectrometer? A. lamp ~> sample ~> detector ~> grating (monochromator) B. lamp ~> sample ~> detector C. lamp ~> sample ~> grating (monochromator) ~> detector D. lamp ~> detector ~> sample E. lamp ~> grating(monochromator) ~> sample ~> detector

E

It's five minutes before your lab period begins and you realize that you are not properly dressed for lab. You could (choose all correct options): A. Return to your residence to get the proper clothing, if time permits. B. Go to the Student Stores to purchase the proper clothing. C. Try to sneak into lab while your TA is not looking. D. Ask a friend to bring proper clothing, if time permits. E. All of the above F. A, B and D

F

You remember that you left your lab manual in your lab room yesterday after leaving Morehead. You stop by the lab room the next day before labs start and find that your lab room is open and no chemical work is being done. Which of the below statements are true? A. You may enter the lab room and pick up your manual because no chemical work is being done in the lab room. B. You must find someone on the lab staff to accompany you into the lab room to pick up the manual that you left behind. C. You must wait until next weeks lab. D. You may email your TA and ask if they can go to the lab room and pick up your manual or meet you to escort you to the lab room. E. All of the above F. B and D G. A and C

F

1. You are permitted to adjust the flow rate if, after your measurement of the flow rate, it is found to be too high or too low? True False

False

1. you will use the partition Coefficient determined in Week 1 to help calculate the percent ethanol in the beer samples? True False

False

2. You can run with less than 3 strips in the electrophoresis tray. True False

False

4. Buffer capacity is at a maximum when pH = pKa + log [A-]/[HA] True False

False

You are permitted to have a bottle of water outside your book bag in the lab room as long as it is securely capped or has a lid? A. True B. False

False

While taking your pre-lab quiz and listening to your pre-lab lecture, you are not required to wear your safety goggles. True False

Fasle

1. What are some common reasons to carry out an extraction? A. isolate the desired analyte B. concentrate the desired analyte C. to modify the desired analyte D. separate the analyte to avoid interference with other species E. All of the above F. A, B & C G. A, B & D H. A, C & D

G

In which of the following locations are you required to have your safety goggles covering your eyes at all time? A. In your lab room. B. In Morehead Labs room 408A, where the TA office hours are held C. In the GC room. D. In the UV/Vis spec room. E. All of the above F. A and B G. A, C and D

G

Which of the following statements is/are correct: A. When leaving the lab room, it is acceptable to leave my gloves on if I have just put a pair of clean gloves on my hands. B. When leaving the lab room with chemicals, I must place them on a cart, or in one of the rubber black carriers to prevent chemicals from spilling in the hallways/elevators. C. When exiting the lab room, I must first take my gloves off and dispose of them in the trash D. When leaving the lab room with chemicals it is ok to carry them in my hand throughout the hallways/elevators. E. When exiting the lab room I must first take off my gloves and dispose of them in the glove recycling containers provided on the same lab bench where I got my clean gloves. F. All of the above G. B and E H. A, B D

G

Briefly (1-2 sentences ONLY) explain why it is important for you not to let the gel stationary phase go dry in a size exclusion column.

If the gel stationary phase dries out, air bubbles will become trapped in the stationary phase which will change the path of the solute molecules.

1. The higher the partition coefficient, the better the solvent is able to extract analyte from the sample matrix. True False

True

1. The temperature of the injection port needs to be higher than the temperature of the column to ensure full vaporization True False

True

3. Ethyl acetate is flammable so needs to be handled with caution. True False

True

6. During a liquid-liquid extraction, the solvent with the lowest density will be on the top. True False

True

My cell phone should remain put away at ALL times while in the lab room. True False

True

Safety is always my number 1 priority in lab? A. True B. False

True

The safety shower should only ever be used if a large volume of chemical is spilled on your skin. True False

True

Your lab coat must stay in the lab room the entire semester? True False

True

2. Proteins with a negative charge will migrate toward the

anode

6. Given what you know about the mobile phases in this experiment, rank mobile phase 1, mobile phase 2 and mobile phase 3 in order from most polar (1) to least polar (3)

mobile phase 1, mobile phase 2, mobile phase 3