Chem 101L Study Guide

This clothing would be appropriate for lab: shows black somewhat loose t-shirt, leggings, and closed toed shoe boots

-Correct -Good coverage, all the way down to the ankle. These would be suitable for lab. However, it is important to note that leggings tend to be absorbent and will not protect from spills as well as cotton or denim fabric.

This shoe would be appropriate for lab: flip-flops

-False -This shoe offers no protection of the toe, heel, or upper part of the foot. This wouldn't work for lab.

Q1, Density: Using the graph shown from an experiment measuring the density of water, what would be the correct value, units, and significance of the intercept of the regression line?

1.034 g/mL represents the density at a temperature of 0 Celsius.

Q5, Gas Forming Rxns and Rockets: The following equations represent reactions used in Experiment 5. Of these reactions, choose the correctly balanced oxidation-reduction reaction.

2 HCl (aq) + Zn (s) → H2 (g) + ZnCl2 (aq) -hints: Zn stands alone and then pairs up with another atom -it's also balanced correctly while some of the other redox rxns aren't

Q2, Aqueous Rxns: For the reaction of 3.5 g of sodium bicarbonate with 30 mL of 0.5 M HCl if the temperature rises from 22.4°C to 32.1°C. The value of ΔT/mol (°C/mol) would be:

233 degrees C/mol - (9.7 degrees C)/((3.5 g)/(84.007 g/mol)) -NaHCO3 was limiting reactant

When the procedure calls for making a more dilute solution of an acid, or mixing an acid with other solutions, what is the correct order of steps?

Always Add Acid (afterwards)- Either add all of the water or non-acid component first, or add a significant portion, before adding the acid to the mixture. This helps to minimize the heat generated, which could otherwise create dangerous fumes or reactions.

Q5, Gas Forming Rxns and Rockets: What does CV measure? How do the numbers correlate?

CV measures precision. The higher the CV, the lower the precision.

Q6, Thermochemistry: In the reaction NaOH(s) + HCl (aq) → NaCl(aq) + H2O(l), the spectator ion(s) would be: (select all that apply.)

Cl-

At what point in a titration does neutralization occur?

Equivalence point: point in titration at which the amount of titrant added is just enough to completely neutralize the analyte solution. At the equivalence point in an acid-base titration, moles of base = moles of acid and the solution only contains salt and water.

Q4, Conductometric titration: The reaction of zinc with hydrlochloric acid seen in experiment 5 produces hydrogen gas via the equation featured below. Which of the following species gets reduced? Zn (s) + 2 HCl (aq) → H2 (g) + ZnCl2 (aq)

Hydrogen

Q4, Conductometric titration: Which of the following can best be described as measuring accuracy?

Percent error -percent difference would be another option but it wasn't listed

Q7, Beer's Law Determination of an Unknown Concentration: When viewed through a spectroscope, calcium ions produce three distinct lines in the visible region of the spectrum, at spectroscope positions of 7.30, 7.85, and 8.45. Assuming the linear fit for the calibration of the spectroscope has a positive slope, the most likely yellow line would be at a position of:

The answer cannot be determined from the information provided.

Q6, Thermochemistry: To carry out Experiment 6 quantitatively, one major adjustment was made to the procedure followed in Experiment 2. That adjustment was:

The calorimeter was calibrated to account for heat loss from the system.

Q4, Conductometric titration: During a conductivity titration, 15.00 mL of 0.00495 M AgNO3 is placed in a beaker with 35 mL of H2O. The predicted end point of the titration with 0.00495 M LiCl was at a volume of 15.00 mL, but the results of titration consistently gave an end point from 12.20-12.31 mL. A well-reasoned explanation for this result would be: (HInt: No calculator is required.)

The concentration of lithium chloride was higher than what was reported on the label. -this makes sense because we needed less of the LiCl, the titrant, to actually reach the endpoint. This means there were more moles of the titrant in the solution than we originally assumed, making the concentration higher

Q8, Spectroscopy, Continuous & Line Emission Spectra: Which of the following is a true statement about the bright yellow flame seen during a flame test of a 1 M solution of NaCl in a Meker burner flame?

The yellow color is characteristic of the changes in energy of an electron in the Na+ metal ion. -tested the color change of electrons in metal ions

This clothing would be appropriate for lab: black t-shirt and jeans

True

Q5, Gas Forming Rxns and Rockets: The following three actions could produce a significant source of error in the results for Experiment 5: -Losing H2 gas because it is much less dense than air. -Collecting gases while the reaction is still hot, resulting in mostly H2O vapor in the bulb. -Leaving moisture on the spark gun tip before firing.

True: all three are examples of random error

Q8, Spectroscopy, Continuous & Line Emission Spectra: In calorimetry, the enthalpy change of the reaction, qrxn, is defined to be: (Select all that apply.)

-(qsoln + qcal) the heat gained or lost by the reaction in units of joules. both are true

When should you be sure to wear full PPE (proper attire, lab coat, goggles) in the laboratory? (Check all that apply.)

-->a. Once the experimental work has begun. -->b. While waiting in the lab room for a friend to finish. -->c. While cleaning up after experimental work is done. -->d. During the lab quiz. -->e. As soon as you enter the lab, and until you are ready to walk out the door. If you are in the laboratory, you should be wearing PPE (or be in the process of putting it on.)

Consider the following scenario: A student has prepared a series of analytical solutions to be run on an instrument in another room. The student has worn gloves throughout the preparation of the solutions, and has wiped up all drips and spills that occurred during that process. The student removes her gloves before leaving the lab room and carries her solutions in scintillation vials in a large clean beaker to the room where the instrument is located. Once in the new room, the student obtains a new pair of gloves before dispensing the solutions for analysis. Which of the following changes could improve the student's procedure? (Check all that apply.)

-->a. The student could have worked with her lab partner so that one of them could carry the materials with gloved hands, while the other opened doors and pressed elevator buttons with non-gloved hands. b. The student should have kept her gloves on the entire time, as she was handling glassware and reagents. Therefore, that takes priority over any contact with doorknobs or elevator buttons, and gloves should be worn. Also, this would conserve one pair of gloves and keep them from being wasted. -->c. The student could have chosen a plastic bin, or other less breakable container to carry her solutions to the instrument so that she wasn't carrying glassware with her bare hands. d. No changes, the student handled the process correctly. -->e. The student could have worn a single glove on the hand she used for transporting the solutions to the instrument room, and used her non-gloved hand for opening doors and pushing elevator buttons.

Suppose a beaker of solid reagent drops onto the bench and cracks. Which of the following represents the correct disposal:

-->a. To the extent possible, solid reagent should be added to the solid waste container and broken glass should be added to the glass waste. Hazardous materials should never be added to the glass waste, and broken glass should only be allowed in the solid waste with the TA's approval. b. To minimize the risk of injury, all materials should be added to the glass waste. c. To maximize the correct disposal of hazardous material, all materials should be added to the chemical solid waste.

In some circumstances, materials that are being heated in the lab could catch fire. If a flammable substance in a beaker should catch fire while you are working but the flames are relatively contained, which method must never be used for extinguishing the flame?

-->a. Use water from the sink nearest the bench to douse the flames. b. Use the chemical fire extinguisher located in the lab. Pull the pin, aim the nozzle into the beaker, and pull the lever. c. Turn off the heat source immediately, and use a watch glass to cover the beaker and minimize the oxygen around the flame.

What is the most important consideration to preserve safety when it is necessary to feed glass tubing, thermometers, or other apparatus through a rubber stopper?

-->a. Using the correct hand position so that if something goes wrong you can avoid coming into contact with broken or sharp ends. b. Using sufficient force that the apparatus will slide through the stopper. c. Using sufficient vacuum grease that the apparatus slides smoothly. d. Letting your TA handle the procedure for you.

Q7, Beer's Law Determination of an Unknown Concentration: When calculating the displacement volume of the thermometer, the volume reading on the buret is 29.37 mL without the thermometer, and 28.72 mL with the thermometer in place. How many significant figures should be recorded for the displacement volume of the thermometer?

-0.65 so 2 sig figs

Q8, Spectroscopy, Continuous & Line Emission Spectra: In the conductivity titration of barium hydroxide and sulfuric acid, 10.15 mL of 4.95 x 10-3 M Ba(OH)2 is titrated by a 4.15 x 10-3 M H2SO4 solution. The end point of the titration would be expected at a volume of: (Hint: no calculator required.)

-12.11 mL -(10.15mL)(4.95*10^-3M)/(4.15*10^-3M)=12.11 mL -key concept: moles of titrant=moles of analyte when titration rxn is complete and neutralization is reached

Q8, Spectroscopy, Continuous & Line Emission Spectra: Given the Rydberg equation: ΔE = RH (1/(nf2)- 1/(ni2)) In the Balmer series for hydrogen, what is the initial energy level (ni) for a photon with a wavelength of 656.3 nm? REMEMBER: h = 6.626 x 10-34 J⋅s; c = 2.998 x 108 m/s; RH = 2.18 x 10-18 J

-2.999~ 3 -Ninitial=(1/sqrt(0.25-(E/RH))

Q4, Conductometric titration: In a conductivity titration, 10.15 mL of 4.95 x 10-3 M Ba(OH)2 is titrated by 12.11 mL of a H2SO4 solution. Given the end point volume of titrant, what is the concentration of the H2SO4 solution? (Hint: No calculator necessary.)

-4.15*10^-3M -((10.15mL)(4.95*10^-3M))/(12.11 mL)= 4.15*10^-3 M -this works because the premise of a titration rxn is that the acid and the base have equal moles at the end of the rxn. M1V1=M2V2 assumes that the moles of each solution is the same.

Q8, Spectroscopy, Continuous & Line Emission Spectra: The graph shows the calibration of a spectroscope against a series of emission lines of known wavelength. Based on this calibration, which is the wavelength of a line that appears at 5.34 mm on the spectroscope scale?

-534 nm -use equation given on the graph

Q7, Beer's Law Determination of an Unknown Concentration: A 1.00-mL sample of a soft drink is diluted with distilled water to 3.50 mL in a cuvet. The concentration of the diluted solution is determined to be 4.58 x 10-6 M in Allura Red AC. Based on this result, what is the mass of Allura Red AC in a 946-mL sample of the drink? (NOTE: The molar mass of Allura Red AC is 496.43 g/mol.)

-7.53 mg -(1) get moles of the sample from that concentration: 0.350L(4.58*10^-6M) -(2) find grams: (0.350L(4.58*10^-6M))*(496.43g/mol) -(3) multiply by .946L= 7.53*1-^-6 g= 7.53 mg

Q6, Thermochemistry: In a calorimetry experiment, 50.0 mL each of two dilute aqueous solutions are combined and produce an extrapolated ΔT = 22.4˚C. If the density of each solution is assumed to be equal to that of water (at 20˚C, d = 0.9982 g/mL), and the specific heat of the solution is also equal to that of water (4.186 J/g˚C), the value of qrxn would be:

-9.36 kJ qrxn=-((50.0mL(2))(0.9982 g/mL))*(4.186 J/gC)(22.4 C)= -9.36 kJ -pro tip: the rxn itself lost heat to the environment, so the answer itself is negative

Which of the following is a behavior that can pose a safety risk in the laboratory environment?

->a. Moving rapidly around the lab to be sure to finish the experiment in time. ->b. Leaving your lab drawer open while you set up your apparatus and obtain your reagents. ->c. Looking away from your work to answer a question from your TA or lab partner. ->d. Staying focused on your own experiment and not being distracted by what nearby groups are doing. ->e. Sitting on lab benches, lab floors, or hallway floors, while waiting for lab to begin or for another student to finish.

If you choose to wear loose clothing, large or dangling jewelry, or contact lenses to lab, which of the following statements best represents how you should proceed?

-Correct: All of these statements are reasonable compromises if you MUST wear these items to lab, but the best and safest practice is to leave them at home and dress for lab intentionally. -Make sure to wear your goggles securely over your contact lenses and check with your lab manual and TA to be sure you will not be working with any volatile or fume-producing reagents. -Make sure all loose clothing or jewelry can be confined by the lab coat -Make sure none of the jewelry will catch on your clothing or accidentally cut your gloves, and don't wear anything too valuable.

While weighing out a reagent for use in an experiment, a student finds he has leftover reagent. The student should:

-Correct: Place the excess reagent in the appropriate solid or liquid waste container to prevent contamination of the stock reagent. -b. Notify the TA immediately. c. Return the excess reagent to the stock bottle to minimize the amount of waste generated. d. Leave the dispensed material out on the bench so that another group can use it, which will minimize the waste generated.

When should you be sure to use a sealed container and/or secondary containment in the laboratory?

-Correct: When transporting materials from one lab room to another. -When heating a solution over a hot plate. -When transporting materials from the hood to the bench. -When heating materials over a Bunsen burner.

Which of the following must be completed as soon as you arrive in lab?

-Correct: everything except for put on your gloves -Store your backpack, cell phone, jacket, and all other nonessential items in designated storage areas. -Put on your lab coat -Tie back long hair -Put on your goggles -Put on gloves

This clothing would be appropriate for lab: t-shirt that doesn't cover shoulders and pants

-False -Shoulders must be covered, even under the lab coat. This attire is not appropriate for lab.

This shoe would be appropriate for lab: mesh covered sneakers

-False -This shoe covers the toe, heel, or upper part of the foot. But, because it is constructed of mesh, it offers no protection from chemical spills; this wouldn't work for lab.

This shoe would be appropriate for lab: closed-toed heels

-False -This shoe offers great protection of the toe, heel, or upper part of the foot. But, because the high heel could cause the wearer to be unstable while moving around in lab, this wouldn't work for lab.

For which of the following situations should you be sure to notify your TA and fill out an incident report form? (Check all that apply.)

-all of the above -You arrive in lab, but realize that your cold medicine is making you feel groggy. -During lab check-out at the end of the semester, your lab partner accidentally drops a beaker, and a small chip of glass causes a scratch on your ankle because you weren't wearing socks. -You accidentally pick up a beaker from the hot plate, not realizing that it was already hot, and the edge of the beaker leaves a small red mark on your thumb. -You begin to feel faint and dizzy in lab because you had to skip lunch. -During check-in you discover a broken funnel in your drawer, and the broken end of the stem causes a small nick through your glove.

Which of the following precautions is important when using a hot plate? (Check all that apply.)

-all of the above a. Set up your work space with the hot plate in a secure location away from the edge of the bench so that you won't accidentally bump it and spill hot or flammable liquids. b. Remember that the ceramic top of the hot plate, and any glassware heated by the hot plate will look the same when hot as cold, and will not cool down until well after the hot plate has been shut off. c. Set up your work space so that wires and cables cannot accidentally make contact with the ceramic surface and melt. d. Never leave the hot plate turned on and unattended. e. Set up the work space so that flammable materials - notebooks, paper towels, other reagents, etc. - are far away from the hot plate to prevent them coming in contact with the hot surface.

8: Spectroscopy

-conclusion: when electrons transition from higher to lower energy levels, they emit photons that can be observed as light. Elements have unique emission spectrums that can be used to determine their respective identities.

Q2, Aqueous Rxns: 5.224 g in a buret segment with a largest volume increment of 50.00 mL shows a corrected volume of 44.3 mL at a certain temperature. How many significant figures will be present in the correct representation of the density?

-d=m/v -(5.224 g)/44.3 mL=0.118 g/mL -3 significant figures

5: gas forming rxns and rockets

-evaluate gas ratio and order of gases added in combustion rxn to yield the farthest rocket launch -oxygen collected from reaction of yeast and hydrogen peroxide -hydrogen collected from reaction of zinc and hydrochloric acid -combination of gases in different orders to optimize rocket launch

2: Aqueous Rxns

-objective: The purpose of this experiment is to use calorimetry to understand the temperature changes that occur in a chemical reaction in aqueous solution. -conclusions: measured physical changes using experimental setup since most of the energy was not lost due to it being a closed system. Surroundings supply energy to break bonds in endothermic reactions and energy is released by the reactants forming bonds in exothermic reactions.

6: thermochemistry

-objective: aim to verify Hess's Law. 2 different rxns' formation enthalpies will be accounted to measure the total heat of each rxn, which will then be summed up to find the third rxn's enthalpy -conclusion: calorimetric methods proved Hess's Law using a combination of rxns' enthalpies involving NaOH, HCl, and water

1: Density & temperature

-objective: measure the effects of temp on water density by measuring water (including distilled, contaminated, and purified) densities at different temperatures -conclusion: inc in temp means dec density

7: Beer's Law

-objective: unknown analyte concentrations measured with Beer's Law equation, A=elc (molar coefficient, path length, and concentration) -aborbance graph measured mg/serving of Allura Red Dye -conclusion: validation of Beer's Law b/c a higher concentration yielded a higher absorbance value for Allura Red AC solution. Powerade's concentration was higher than Gatorade's.

4: conductometric titration

-purpose= determine the effects of decreasing ionic concentration on the conductivity of the solution. The rxn we are monitoring is the combination of AgNO3 and LiCl which will make AgCl as the precipitate and leave LiNO3 in aqueous state. The conductivity decreases as the rxn progresses b/c the small bits of Cl- react with Ag+ leaving behind AgCl(s) -conclusion: titration allowed us to find the concentration of the unknown solution through the Conservation of Matter & the compounds' balanced equations.

Order the following steps you would take if you find broken glassware in your lab drawer, or if a piece of glassware breaks during the lab.

1. notify TA so they can help you 2. use a pair of leather gloves found in lab room to prevent nicks or cuts 3. NOT: pick up large pieces immediately using the regular lab gloves. 4. Use the dustpan and brush found in the lab room to sweep up small shards and chips in the area where the glassware was broken and dispose of these in the designated glass waste.

Q2, Aqueous Rxns: The molecular equation of a reaction is NaHCO3(aq)+HCl(aq)-> NaCl(aq)+H2O(l)+CO2(g). Both the initial solutions and the final solution were transparent and colorless, but bubbles were seen during the reaction. Based on this equation and the observations of the reaction, the spectator ions in the ionic equation would be:

2 of the above: Na+(aq) and Cl-(aq)

Q1, Density: When calculating the displacement volume of the thermometer, the volume reading on the buret is 28.47 mL without the thermometer, and 27.82 mL with the thermometer in place. How many significant figures should be recorded for the displacement volume of the thermometer? Select one:

28.47mL-27.82mL=0.65mL 2 sig figs!

Q5, Gas Forming Rxns and Rockets: According to the stoichiometry of the exothermic reaction equation 2 H2(g) + O2(g) →2 H2O(g), the maximum energy that can be released by this reaction would occur at a H2:O2 ratio of

2:1 (look at reactants' side)

Q2, Aqueous Rxns: A buret segment with a largest volume increment of 35.00 mL is filled with pure water to approximately halfway between 19.2 and the mark above it. After adding the probe, the meniscus moves to halfway between 18.9 and the mark just under it. What is the original volume of the water in the buret?,

35.00mL-19.15mL= 15.85 mL

Q1, Density: The volume marking at the sealed bottom of a buret segment is 38.60 mL, and has markings for every 0.1 mL. When water is added, the bottom of the meniscus sits about halfway between the line for 18.3 mL and the next mark up. What volume of water is contained in the buret segment?

38.60mL-18.25mL= 20.35mL

Q7, Beer's Law Determination of an Unknown Concentration: A Beer's law calibration curve for a particular analyte has a best-fit equation of A=(11765 M-1)C + 0.197, with an R2 value of 0.9373. If a sample solution has an absorbance reading of 0.811, the concentration of the unknown sample would be:

5.2*10^-5 M

Q4, Conductometric titration: A conductivity plot for the titration of silver nitrate with lithium chloride is shown below. Assuming lithium chloride is the titrant, which ion species would you expect to be found in solution when 4.62 mL of titrant had been added?

AgNO3(aq)+LiCl(aq)->AgCl(s)+LiNO3(aq) -answer: Ag+,NO3(aq), & Li+ (aq) -LiCl(aq)= titrant, small amounts -AgNO3(aq)= analyte, tons of it in beaker -key thing to remember: we had lots of AgNO3 (aq) but only add small amounts of LiCl (aq), so the Cl was all used up (wasn't in the solution any more) because it was forming AgCl (s) which isn't considered part of the solution since it's not aqueous. Ag was still in the mix because AgNO3 (aq) had tons of Ag, NO3 was still in the mix b/c AgNO3 had tons of it, and Li was still in the mix because it was still in the solution (aqueous). The only species that wasn't present in the mix was Cl as it was forming a precipitate which isn't part of the solution.

Q6, Thermochemistry: The molecular equation for the reaction previously done in Experiment 4 is: Ba(OH)2 (aq) + H2SO4 (aq) → BaSO4 (s) + 2 H2O (l). How is conductivity reflected in the net ionic equation?

Barium hydroxide is a soluble ionic substance that is highly conductive in solution, and sulfuric acid is a strong acid that also conducts strongly in solution. In contrast, barium sulfate is an ionic solid, and, as a solid, it is nonconductive. Water is a covalent substance that is also a nonconductor. Therefore, the net ionic equation will have no spectator ions, and only the reactants will be written as ions in solution.

Order the following steps in the correct procedure for lighting and working with a Bunsen burner:

Correct order of steps: 1. Make sure all hair and loose clothing is properly restrained 2. Prepare workspace so that no flammable objects are in sight 3. Inspect the tubing on the gas valve to ensure no cracks that would cause gas leak 4. Inspect the burner to ensure air intake and gas valves move properly and can be adjusted 5. With the sparker in hand, turn on the gas and light the flame ASAP to mimize unburned gas in the air 6. 7. Monitor the flame and nearby objects until experiment is complete. Never leave a flame unattended. 8. Shut off the burner and gas valve as soon as experimental work is completed (or any time you must leave it unattended) -First, take any personal safety precautions that are warranted. -Second, prepare your workspace. Third, inspect your equipment to be sure it is functioning properly. -A note about Bunsen and Meker burners: The fuel valve determines how quickly fuel is supplied to the combustion, which determines the flame height. The air intake determines how quickly oxygen is supplied to the combustion (how lean/rich the mixture is), which determines the flame temperature.

Q6, Thermochemistry: A colored metal salt was dissolved in 120 mL of distilled water. Using a known spectroscopic method, the metal was shown to have a concentration of 6.102 x 10-5 M. Titration of the sample with a known hydrochloric acid solution showed 2.3 x10-5 mol of the anion. What is the identity of the salt tested? (Hint: Pay attention to units. While a calculator can help it is not necessary.)

Cr(OH)3 -(2.3*10^-5M)/((0.120 L)(6.102*10^-5M))=3.14 ~3 -found the ratio of the anion to the cation to be 3:1, so the anion must have a subscript of 3

Q2, Aqueous Rxns: The temperature at the start of a reaction was 22.8 degrees C and the final temperature was 32.9 degrees C. Based on these observations, the reaction of the sodium bicarbonate with hydrochloric acid would be:

Exothermic, because energy was transferred from the reaction to the surroundings.

Q5, Gas Forming Rxns and Rockets: Two calorimetry trials were performed with barium hydroxide and ammonium chloride. The first, using 2.0 g of barium hydroxide with 10 mL of a 0.5 M ammonium chloride solution showed a temperature change from 23.2 oC to 12.5 oC. The second trial showed a decreased from 25.7 oC to 20.4 oC after addition another 10 mL of 0.5 M ammonium chloride to 1.0 g of barium hydroxide in the calorimeter. What does this observation suggest about the reaction.

The reaction of barium hydroxide and ammonium chloride is endothermic. The energy absorbed is directly related to the difference in the initial temperature upon mixing the substances -temp decreases in both trials: the rxn is endothermic -energy absorbed is directly related to the moles of the substances reacting (not the temperature bc temp is just an effect of the rxn occurring)

Q1, Density: A student creates the following graph after an experiment measuring the density of water. Suppose the thermometer the student used was improperly calibrated and always read a value 3.5 degrees below the true temperature. Which of the following statements would be true?

The slope of the regression line would be correct, but the intercept would read a value that was less than the true value.

How many times should you read the label on a reagent container and compare it with the lab manual?

a. At least once. -->b. At least twice each time you remove material from the container. c. At least twice.

Which of the following is the reason backpacks must be stored during lab?

a. Backpacks on the floor present a tripping hazard to students in lab, which may lead to spills and other incidents. -->b. Both of these are good reasons to keep nonessential items stored properly c. Backpacks on the floor of the lab or on the benches may be exposed to hazardous materials, which might then lead to student exposure outside the lab.

When reading the label on a reagent container, what are the three most important pieces of information?

a. CAS Number b. Color c. Chemical formula -->d. Hazard warning(s) -->e. Name -->f. Concentration

Your lab partner accidentally gets a mist of your solution in her eye. You immediately help her to the eye wash to rinse it. After about a minute, she feels better and is ready to get back to work. You should:

a. Check to see if her eye is still red. If not, hurry so that you can finish the experiment -->b. Keep her in the eye wash for at least 15 minutes, and then make sure she goes to student health, just to be sure. c. Let the TA inspect her eye to see if it is okay. d. Keep her in the eye wash for at least 5 minutes and then let the TA decide if she can continue working.

When should you inspect the glassware in your lab drawer for chips, cracks, or chemical residues?

a. During check-in, when any suspect glassware can be replaced for free. b. Before beginning every experiment. -->c. Glassware should be inspected at all of these times to prevent accidents, injuries, or unwanted complications during experimental work. d. During an experiment, before using any piece of glassware.

If you need to work with a flammable or volatile solvent, which piece of lab equipment should you be sure to use?

a. Heating mantle. b. Volumetric flask. c. Hot plate. -->d. Fume Hood with good ventilation. e. Bunsen or Meker burner, or anything with an open flame.

Your lab partner accidentally spills some acid on his wrist and watchband. You should: (Check all that apply.)

a. Rinse the watch band before allowing him to put it back on. b. Take him to the safety shower, and make sure he stands under it for at least 15 minutes to be sure all hazardous material has been washed away. -->c. Remove the watch and watchband immediately, and rinse his wrist for at least 15 minutes to be sure all hazardous material has been washed away. d. Let the TA inspect his wrist to see if it is okay.

In some circumstances, materials that are being heated in the lab could catch fire. If a flammable substance in a beaker should catch fire while you are working but the flames are relatively contained, what is a simple method for extinguishing the flame?

a. Use water from the sink nearest the bench to douse the flames. -->b. Turn off the heat source immediately, and use a watch glass to cover the beaker and minimize the oxygen around the flame. c. Use the chemical fire extinguisher located in the lab. Pull the pin, aim the nozzle into the beaker, and pull the lever.

What is your BEST resource for understanding the nature of the chemical hazards of materials you work with in lab?

a. Your TA, or other TAs you visit during office hours. b. The label on the reagent bottles found in the fume hood. c. Your friend who took the lab last semester and saved his notes. -->d. Safety Data Sheets (SDS) that should be consulted before coming to lab each week.

Q7, Beer's Law Determination of an Unknown Concentration: In Experiment 7, the ultimate purpose of creating the Beer's Law plot of absorbance vs. concentration of Allura Red AC is best described as:

to determine the mg/serving of Allura Red AC in a solution prepared from a drink sample.