Laboratory Organization. A logical and complete organizational system is essential to the smooth, efficient functioning of the general chemistry laboratories. GH109 and 110, the general chemistry laboratories, are organized according to the following guidelines:
PLEASE LEARN THE ORGANIZATIONAL SYSTEM AND EXERT THE EFFORT REQUIRED TO MAINTAIN THE CLEANLINESS AND THE ORGANIZATION OF THE LABORATORIES. THIS IS YOUR RESPONSIBILITY!
Conservation of Supplies. Items normally considered disposable are recycled in the general chemistry lab. These items include
These items must be washed and glass items must be oven dried following use, then returned to their appropriate storage locations.
Cleaning Glassware. All glassware to be used by students in experiments must be CLEAN. Ideally, each section of students will thoroughly clean the glassware that they have used and place it in the drying oven, so that it will be ready for a subsequent section. In practice, however, students will avoid cleaning glassware if they can get away with it. It is each student's responsibility to properly clean all glassware that s/he uses. However, IT IS YOUR RESPONSIBILITY TO MAKE SURE THAT THE STUDENTS DO THIS. If the students do not clean it, then the responsibility falls to you. A faculty member finding dirty glassware left over from a lab section will seek out the responsible TA to perform the clean up.
Cleaning protocol:Hazardous Waste Collection and Disposal. It is not too much of an exaggeration to say that virtually everything except distilled water is considered to be hazardous waste, and must be handled and disposed of according to EPA (Environmental Protection Agency) guidelines. Hazardous waste disposal is overseen by Mr. David Messier (email: dmessier@wpi.edu), who supplies labels for hazardous waste containers and picks up full containers by appointment. With few exceptions, reagents and solvents used by students must be collected in appropriate containers and disposed of via Dave Messier.
A few substances can still be disposed of in the sink drains, accompanied by a substantial water flush. These include
All other materials must be collected in bottles with official hazardous waste labels. Labels must be properly filled out with the names and weight percentages of the component materials, and toxicity, corrosive ability, potential flammability, and potential reactivity must be indicated. OMISSION OF ANY OF THIS INFORMATION IS A VIOLATION OF EPA POLICY.
Three categories of waste will commonly occur in the general chemistry labs:
When any of these three categories of substance is to be used in a general chemistry experiment, THERE MUST BE PROPERLY LABELLED AND SIZED WASTE CONTAINERS AVAILABLE IN ALL HOODS IN GH109/110. Again, it is your responsibility to inform students of the need to properly dispose of these substances, to show them where and how to do it, and to make sure they do it.
Safety Matters
The following safety matters must be vigorously and strongly addressed:
Weekly TA Laboratory Meetings. It is our policy that all general chemistry TAs should carry out each experiment in advance of the week in which the experiment is to run. This serves several purposes.
Doing the experiment in advance makes you more of an expert, and better able to teach the students about the experiment. It enables you to learn lab techniques that you may not have experienced, and therefore are not in a position to teach.
We expect you to take the lab run-throughs seriously; to come on time, to follow the rules (wear your safety glasses), to focus on the experiment at hand, to carry it out to the best of your ability, to pinpoint problems, to offer solutions, and generally to contribute to making the lab program one of high quality. To competently teach the lab, you must have as thorough an understanding of each experiment as your are capable of achieving.
Lab Protocol
Please print a fresh copy of the experiment in the AM before you meet your section so that you are up-to-date on any changes.
Please arrive at least 30 minutes before your lab is to begin, so that you can make sure that all required materials are available, turn on instruments if necessary, and prepare the blackboard if necessary.
When you arrive in lab, please go through a mental checklist to make sure that everything is ready to go for the experiment. Ask yourself the following questions:
Getting everything together and ready prior to lab is your responsibility. Scurrying around for stuff that you forgot during the lab is unprofessional--please don't do it.
Please collect the Preparation Questions (prelab) from students as they enter the lab. Students should not work on these during the laboratory.
Please circulate during lab and query students about their activities.
Please use the full 3 hours of the laboratory period. A pair of students that
within the 3-hour lab period may leave when finished. ALL OTHER STUDENTS MUST REMAIN FOR THE FULL 3 HOURS. Those students for whom the 3-hour period is not enough to complete the notebook writeup may turn in their notebooks before 4 PM on the following day. Students have paid for a 3-hour lab period. We owe that time to them, and they owe it to us!
Please be sure that you understand how an aspirator trap functions. The proper way to close off the atmosphere vent is to fold the vent tube over, then clamp it with a screw clamp. The aspirator trap should be set up as follows: the hose connected to the long glass tube going thru the rubber stopper should be connected to the aspirator sidearm of the faucet. A short piece of tygon tubing should be placed on the short glass tube going thru the rubber stopper; this is the atmosphere vent. The hose attached to the sidearm of the test tube should be connected to the student apparatus requiring suction.
As students finish the experiment,
Some important DON'TS:
In each lab period, we will teach the students via demonstration at least one basic laboratory technique. Please learn each technique correctly, practice it, and add it to your laboratory repertoire.
Initial Laboratory Meeting
The first laboratory meeting in CH1010 must be used to get the new freshman student off on the right foot. It serves a dual purpose. First, students must be oriented to the laboratory. Second, they must perform the first experiment. The orientation phase, which will usually be handled by the responsible faculty member, should take about 1 hour. Following orientation, 2 hours will remain in which the students can perform the first experiment.
Orientation. Included in the orientation phase of the first meeting should be
Experiment. Following the orientation, the faculty member or TA should give a prelab briefing on the first experiment. The students should then perform the experiment.
Setting Up for the Lab
Locate the materials for the experiment, which should be stored in a cabinet in GH110. They include
Make sure a table showing the density of water as a function of temperature is posted in the lab.
Turn on analytical balances.
Prelab Briefing
In your prelab briefing, you should deal with the following things:
You are not expected to discuss background theory at all in your prelab briefing.
Running the Lab
Students should work in groups of 2. Assign each group a sample of metal for which they are to determine the density.
Circulate while students work. Question them about what they are doing and why.
Make sure students place used Pasteur pipets in the drying oven before they leave. Collect all pycnometers, which should be emptied of water and metal sample.
Make sure the balances and balance area are clean before leaving lab.
Setting Up for the Lab
Locate the materials for the experiment, which should be stored in a cabinet in GH110. They include
Prelab Briefing
You are not expected to discuss background theory in your briefing.
Be sure to:
Running the Lab
There may be other salient observations as well.
Setting up for the lab.
Locate the materials for the experiment which are stored in a cabinet in GH110. They include
In each hood, set up
Running the Lab
Students should work in pairs.
Students will need guidance with filtration procedures. Help them on an individual basis.
Setting up for the lab
2) Preparing supplies of substances
a) Duplicate sets of reagents
Arrange solvent and pure substances at a convenient location in each lab. An alphabetical arrangement of substances is preferred.
3) Set up waste bottles in the hood for
Pre-lab Briefing
You are not expected to discuss background theory.
You should cover the following topics:| Row 1,Hole 1 Solvent 1 | Row 1,Hole 2 Solvent 2 | Row 1,Hole 3 Solvent 3 |
| Row 2,Hole 1 Substance 1 | Row 2,Hole 2 Substance 1 | Row 2,Hole 3 Substance 1 |
| Row 3,Hole 1 Substance 2 | Row 3,Hole 2 Substance 2 | Row 3,Hole 3 Substance 2 |
| Row 4,Hole 1 Substance 3 | Row 4,Hole 2 Substance 3 | Row 4,Hole 3 Substance 3 |
To save time, recommend that students calculate the mass of, say, substance 1 required to prepare 1 mL of a 0.1 M solution; to weigh out 3 x this mass; and to partition this total equally among the 3 well-plate depressions for the substance.
Running the Lab
1) Assigning solvents and substances to students.
30 subsets of the master list of substances/solvents are available. Each subset includes water plus 2 other solvents, 10 or 11 pure substances, and 12 household products. Please print these out for distribution to your students.
Each pair of students in a section should be assigned one of the subsets. Give the subset sheet to the student pair, and instruct them to return it to you filled out before leaving lab. If you have more than a total of 30 student teams in ALL of your sections, you should make copies of some subsets to cover the number of student teams in excess of 30. For example, if in your 3 sections you have a total of 36 student teams, you will need to make copies of 6 of the subsets in order to cover all 36 teams. You should, of course, also keep copies of the subsets for yourselves.
2) Conducting the experiments. Conductivity tests involving the solvent, dichloromethane, should be carried out in the hood. Other tests, including glacial acetic acid solvent, may be done on the lab bench.
3) Disposal priorities
Priority 1: Heavy metal waste--heavy metal waste jar
Priority 2: Chlorinated organic compounds--chlorinated organics waste bottle (1 L)
Priority 3: non-chlorinated organic compounds--nonchlorinated organics waste bottle (4 L)
Priority 4: non-heavy metal inorganics--most can be flushed
Thus a sample that contains, say, acetone and a heavy metal compound must be placed in the heavy metal waste. A sample that contains dichloromethane and NaCl must be placed in the chlorinated solvent waste, etc.
TA resultsSetting Up for the Lab
Locate the molecular model kits in a locked cabinet in GH109a. Inspect all kits for correct content (inside of lid), make up from spare parts kits if necessary.
Prelab Briefing
The purpose of the workshop is to learn something about VSEPR by building models of covalent molecules based on Lewis structures. The models show us what we believe the molecule looks like in 3-D.
Students should be told to
You may have to teach students how to draw Lewis structures. We went thru a systematic approach, which is detailed in Chapter 3 of Concepts of Chemistry. This chapter also discusses VSEPR.
Running the Lab
Circulate and help students when they run into trouble. Make sure they build the structures correctly, and address all of the questions.
Setting Up for the Lab
Prelab Briefing
Demonstrate proper pipetting technique. Stress the need for accuracy in pipetting.
Demonstrate the process of filtration thru a plugged Pasteur pipet
Remind students how to carry out a Hirsch funnel filtration.
Remind them that each pair of students will do two experiments using assigned volumes of NiCl2 and Nadtc stock solutions. They are to record final height data before leaving the lab.
Caution them about contaminating the stock solutions. Show them how to properly place the bottle caps on the bench when accessing the stock solution bottles.
Running the Lab
Circulate, help students master the techniques.
About halfway thru the experiment, you should obtain a bin of ice for the rextallization part of the expt.
As students finish their filtrations, collect their Pasteur pipet filters and arrange them according to Ni/dtc ratio. When all filters have been collected, students can measure and record data on the data collection sheet.
Setting Up for the Lab
Locate the crystal model kits and make sure that there are sufficient balls of each color for each kit. Station the kits in one of the labs, 4 kits per bench.
Prelab Briefing
Briefly tell the students that they will be making models to represent the lattices of crystalline solids. They will begin by looking at closest packing and unit cells in metals, and will proceed to ionic solids during the lab. Review the atom counting rules (vertex, edge, face, and body). These have now been put directly in the lab procedure.
Running the Lab
Students have trouble interpreting the directions in some places, and unless watched tend to "skip by" some of the steps without seeing what they are supposed to see. It is very important to circulate constantly during this lab to make sure all of the students are looking at the models correctly.
Setting Up for the Lab
Locate or prepare 25- or 50-mL dropper bottles containing tetrachloroethane (solvent), acetone (solute), isopropanol (solute), ethanol (solute), and methylethyl ketone (solute). Place these in the hoods in one of the labs.
Locate 1-mL GC syringes in the instrument room.
Check out all 3 gas chromatographs for proper operation. Verify for each GC that gas tanks of He, H2, and air are reasonably full.
Prelab Briefing
Note: Because the lab will be run in two 1.5-hour shifts, the prelab briefing must be no longer than 30 minutes.
Though it is discussed in the background section, discuss in simple terms how gas chromatography works, and how the instrument is designed. Spend some time explaining the significance of the GC Attenuation setting.
Set up the problem to be investigated. The goal is to examine the manner in which a (liquid) solute partitions itself between two (immiscible) solvents, water and tetrachloroethane. Based on the distribution, one can draw conclusions about the relative strengths of intermolecular forces that operate between the solute molecules and the molecules of each solvent. If a particular solute prefers to be in the tetrachloroethane layer more than the water layer (as judged by the sizes of GC signals for the solute arising from the two layers), it is reasonable to conclude that this is a result of more favorable intermolecular forces between the solute and one of the solvents. The first purpose of the experiment then, is to find out which of the two solvents is favored by a particular solute, and to try to understand this in terms of the molecular structures of solute and solvent. Students should then predict which solvent will be favored by a second solute before they actually investigate it.
Running the Lab
Because this is an instrument lab, there is the usual potential problem of too much time spent standing around waiting for instrument access. To solve this we will use a "shift" system. In advance of the experiment, students in a section will be notified by email that half of them are to come at the regularly scheduled time; and the other half are to come 1.5 hours later. When the first group of students arrives
When the second group arrives, give them the prelab briefing. The first group can continue on the GCs during the briefing, but must stop when the second group is ready to enter the instrument room.
Students can, if motivated, discover the equilibrium concept from this experiment. Their GC data should show the RATIO of the concentration (signal area) of solute in solvent 1 to that in solvent 2 is the same in all experiments (the original expt with equal volumes of the two solvents and 5d solute; after addition of more of one of the solvents; and after addition of more solute):
This is the so-called partition coefficient. It is less than 1 when the solute prefers TCE, and greater than 1 when the solvent prefers water. You can discuss this during your prelab briefing if you want.
Setting Up for the Lab
Prelab Briefing
Students are expected to have read the Background section of the experiment before coming to class, so all you should do in the prelab briefing is distribute the data and remind students what they are expected to do (discover the functional relationship between the 4 variables by making appropriate plots of the data). They should spend the 3-hour lab period making hand plots, then should redo the plots on a spreadsheet after the period is over.
Running the Lab
Students may need hints at various points in order to make progress. For example,
Guide them to the general form
w = K*y*(z + C4/C3)/xAsk them how to determine the value of K
Setting Up for the Lab
The following items should be available in the lab:
Prelab Briefing
Discuss the fundamental equation of calorimetry, q = -CcalDT.
Discuss the logistics of collecting time-temperature data.
Running the Lab
Collect the Preparation, then give your prelab briefing.
Each pair of students should be assigned two volumes of one of the acids to react with 50 mL of NaOH solution.
Circulate, discuss technique with students, discuss what they expect their results to show.
As students obtain data, prod them to think about whether or not their results are self-consistent.
When students finish, they should rinse and return the calorimeter and stirrer, thermometers, graduates, and storage beakers.
Setting Up for the Lab
Locate the reagents and equipment for the experiment, which include
Set up the Spectronic 20 spectrometers, power them up. Power up the Hitachi U-2000 spectrometers.
Set up top-loader balances.
Prelab Briefing
Briefly go over the experimental procedure, but do NOT give away the stoichiometry of the reaction. Remind students of the steps involved in suction filtration.
Running the Lab
Circulate while students are working; ask them what they have observed; give them tips on techniques.
As students finish, be sure they
Setting Up for the Lab
Locate the equipment and reagents for the experiment, which should be in a cabinet in GH110. They include
Locate large beakers for use as water baths.
Be sure a tank of nitrogen gas equipped with a regulator is available.
Measure and record atmospheric pressure (barometer in GH07).
Prelab Briefing
Give a detailed explanation of the experimental procedure.
Running the Lab
Circulate and make sure students carry out the procedure properly. Some things to watch out for:
Setting Up for the Lab
Locate the required equipment and materials:
Prelab Briefing
Briefly discuss the solubility product concept.
Running the Lab
This lab is straightforward. Students should do the experiment in duplicate. In the second run, they should take a mass of salt calculated to produce temperatures falling between the temperatures observed in the first run.
Setting Up for the Lab
The following reagents should be available:
Prelab Briefing
Your briefing should not give away any of the expected experimental results. However, you should emphasize to students that their goal is to use Le Chatelier's Principle and their observations to complete the partial chemical equation presented in the Background section of the experiment. The results of their qualitative experiments should be sufficient to allow them to write a complete equation.
Running the Lab
Circulate; encourage students to apply Le Chatelier's Principle to make the connections between their experimental observations and the partial chemical equation in the Background section.
Setting Up for the Lab
You will need to make available the components of a microburet:
Solutions of acids and bases must be available:
Prelab Briefing
Running the Lab
Setting Up for the Lab
Locate pH meters in GH109A. Make available microburet components.
A number of solutions must be available:
Prelab Briefing
Running the Lab
Setting Up for the Lab
Prelab Briefing
Running the Lab
Setting Up for the Lab
Locate the notebook containing NMR spectra of unknowns.
Prelab Briefing
Students should already be pretty comfortable with NMR, so your briefing does not have to be extensive. You may want to have them predict a spectrum from structure, and assign a structure from spectrum to make sure everyone is up to speed.
Running the Lab
Students should work in groups of 3. Each group should be assigned a molecular formula. Group members should figure out all possible isomeric arrangements consistent with the formula, and should predict the appearance of the NMR spectrum for each. Once they have done this, give them the NMR spectra for all unknowns with that formula, and tell them to deduce the isomeric structure that gives rise to each spectrum.
Grading Scheme
Setting Up for the Lab
Locate the large desiccator in GH109A. This contains NaCl crystals, crystal holders, and instrument mounting plates.
Locate the samples in a cabinet in GH110. These should be in small plastic bottles.
Prelab Briefing
Briefly discuss the type of molecular motion that is observed in IR spectroscopy.
DEMONSTRATE sample preparation technique and cell handling for liquid samples.
DEMONSTRATE sample preparation technique and cell handling for solid samples.
DEMONSTRATE the operation of the FTIR spectrometer and associated computer.
Running the Lab
Because there are only 3 FTIR spectrometers, students should be assigned to 6 groups, 2 groups per instrument.
Assign two liquid and two solid samples to each group.
Before running any spectra, each group should draw the structure for each of its assigned samples, and should predict the general appearance of the IR spectrum, focussing on stand-out features such as O-H, N-H, C-H, C=O, and C(3)N stretches.
Each group should print each spectrum only once. If they want additional copies of their spectra, they can photocopy the originals following the lab.
Grading Scheme
Setting Up for the Lab
| Benzaldehyde(2.0M) | Acetone(1.00M) | NaOH(3M) | Comment |
|---|---|---|---|
| 12 mL | 12 mL | 27 mL | total volume, one experiment |
| 18 mL | 18 mL | 40.5 mL | with 50% excess |
| 900 mL | 900 mL | 2024.5 mL | total volume, 50 experiments |
| 1.8 | 0.900 | 6.07 | moles solute needed |
| 190.8 | 52.2 | 243 | grams solute needed |
In this experiment, we assume that the cloudiness always appears after the same amount (number of moles) of product has been produced, since we always work in the same total volume. Thus the inverses of the measured times give us a measure of the rate. We cannot obtain an actual rate in molarity per time, because we do not know how much product has been produced at the point of cloudiness (only that the amount is the same in every case).
Suppose that in one experiment, your average time was 40 seconds, and in the next experiment, 80 seconds. Then the rates for the 2 experiments would be proportional to (NOT equal to) 1/time:
So its clear that the first rate is twice as large as the second.
Similarly, in two experiments in which the concentrations of all participants (benzaldehyde, acetone, and OH-) are the same, the reciprocal of the measured time is proportional to the rate CONSTANT. This is relevant to the temperature data. A plot of 1/t versus T is equivalent to a plot of k versus T, as long as the 1/t values are all obtained under the same concentration conditions.
Potential pitfalls include:
Sample data:
| T | Vol benz | vol acetone | vol EtOH | vol H2O | vol NaOH | time,s |
|---|---|---|---|---|---|---|
| 20 | 0.5 | 0.5 | 1.0 | 123 | ||
| 20 | 0.5 | 0.5 | 1.0 | 130 | ||
| 20 | 0.5 | 0.5 | 1.0 | 129 | ||
| 20 | 0.5 | 0.5 | 0.5 | 0.5 | 249 | |
| 20 | 0.25 | 0.25 | 0.5 | 1.0 | 271 | |
| 20 | 0.25 | 0.25 | 0.5 | 1.0 | 272 | |
| 0 | 0.5 | 0.5 | 1.0 | 462 | ||
| 40 | 0.25 | 0.25 | 0.5 | 1.0 | 12 |
Prelab Briefing
Running the Lab
Setting Up for the Lab
Solution Preparation:
Pipet 50-mL aliquots of the stock solution to beakers, and use 6 M HCl or 6 M NaOH to adjust the solution pH to the values specified above. Then transfer to labelled storage bottles.
Power up thermostat baths, set for 35 oC.
Set up and power up Spectronic 20 spectrometers. Power up Hitachi U-2000 spectrometers.
Set out plastic spectrometer cuvets.
Prelab Briefing
Running the Lab
Setting Up for the Lab
Solution Prep
0.2 M KI solution--dissolve 33.2 g KI in enough water to give 1.00 L of solution.
0.2 M Na2S2O3 solution--dissolve 31.62 g Na2S2O3 in enough water to give 1.00 L of solution.
0.4 M H2O2 solution--Add 35.34 mL of 30% H2O2 to enough water to give 1.00 L of solution.
0.2% by weight starch solution--Slurry 2 g soluble starch in enough water to give 1.00 L of solution. Heat the slurry over a burner until the starch dissolves.
Buffer solutions, pH 2.2 to 8 at 20 oC. These solutions are prepared by mixing various volumes of two solutions, A and B, to give a total volume of 20 mL. Solution A is 0.4 M sodium hydrogen phosphate (Na2HPO4) prepared by dissolving 143.2 g of Na2HPO4.12H2O in distilled water to give 1.0 L of solution. Solution B is 0.2 M citric acid prepared by dissolving 42.0 g of H3C6H5O7.H2O (or 38.4 g H3C6H5O7) in sufficient distilled water to give 1.00 liter of solution. Addition of 3-5 mL of ethanol will retard the growth of mold.
| mL Solution A | mL Solution B | pH |
|---|---|---|
| 0.40 | 19.6 | 2.2 |
| 1.24 | 18.76 | 2.4 |
| 2.18 | 17.82 | 2.6 |
| 3.17 | 16.83 | 2.8 |
| 4.11 | 15.89 | 3.0 |
| 4.94 | 15.06 | 3.2 |
| 5.70 | 14.30 | 3.4 |
| 6.44 | 13.56 | 3.6 |
| 7.10 | 12.9 | 3.8 |
| 7.71 | 12.29 | 4.0 |
| 8.28 | 11.72 | 4.2 |
| 9.35 | 10.65 | 4.6 |
| 9.86 | 10.14 | 4.8 |
| 10.30 | 9.70 | 5.0 |
| 10.72 | 9.28 | 5.2 |
| 11.15 | 8.85 | 5.4 |
| 11.60 | 8.40 | 5.6 |
| 12.09 | 7.91 | 5.8 |
| 12.63 | 7.37 | 6.0 |
| 13.22 | 6.78 | 6.2 |
| 13.85 | 6.15 | 6.4 |
| 14.55 | 5.45 | 6.6 |
| 15.45 | 4.45 | 6.8 |
| 16.47 | 3.53 | 7.0 |
| 17.39 | 2.61 | 7.2 |
| 18.17 | 1.83 | 7.4 |
| 18.73 | 1.27 | 7.6 |
| 19.15 | 0.85 | 7.8 |
| 19.45 | 0.55 | 8.0 |
Prelab Briefing
Running the Lab
Setting Up for the Lab
Students should do this experiment in groups of 3. We need sufficient solution for 30 groups. Each group will require about 5 mL of each "cocktail"; about 0.5 mL of glucose oxidase stock solution; and about 1 mL of glucose stock solution. All solutions should be prepared using pH7 phosphate buffer.
Glucose oxidase stock solution: Dissolve 2.5 mg of glucose oxidase in enough phosphate buffer to give 100 mL of solution. STORE SOLUTION AT JUST ABOVE 0 oC UNTIL THE DAY OF THE EXPERIMENT.
Glucose stock solution: Dissolve 18.0 g of D-glucose in enough phosphate to give 100 mL of solution.
ABTS/HRP stock solution: Dissolve 0.2744 g of the diammonium salt of ABTS in phosphate buffer to give a total volume of 10.00 mL. Add 40 microliters of horseradish peroxidase suspension.
0.1 M Phosphate Buffer, pH 7: Dissolve 1.200 g NaH2PO4 in distilled water to give 100 mL of solution. Add small volumes of concentrated NaOH solution to bring pH to 7.00.
Cocktail #1. Use the following volumes of the above solutions to prepare 100 mL of cocktail:
Cocktail #2. Use the following volumes of the above solutions to prepare 100 mL of cocktail:
Requirements for one group of 3:
Total requirements for 30 groups:
Add 50% for waste.
Prelab Briefing
Running the Lab
The 8 AM labs will be done in shifts--see yesterday's email. Students will work in group of 3. This will give 10 groups in a section.
In addition to the 3 spectrometers in the general chem lab, there are 2 downstairs in GH07 that we can use. So assign 2 groups per spectrometer. Groups will carry out alterate 6-minute runs at the spectrometer.
We will need two sets of reagents (cocktails 1 and 2, glucose stock, glucose oxidase stock), one in 109A and one for downstairs.
Please SIGN OUT a stopwatch to each group that does not have one.
For kinetics runs, students should mix the reagents directly in the cuvet, shake the cuvet, and place it in the spectrometer. They should take an absorbance reading at each minute mark, ending at 6 minutes.
With 2 groups per spectrometer, the total minimum time required to obtain data is 7 runs per group * 6 min per run * 2 groups = 84 minutes. This cuts it close, so they will have to work efficiently.