Solution Manual for Chemistry A Molecular Approach, 4th Edition

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INSTRUCTOR MANUALFORLABORATORYMANUALJOHN B. VINCENTANDERICA LIVINGSTONCHEMISTRYA MOLECULAR APPROACHFourth EditionNIVALDO J. TRO

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iiTable of ContentsExperiment1LaboratoryBasics: Accuracy andPrecision–Who’s theShootingChampion?1Experiment2Components of a Mixture–WhatIsThatStuff in theBottom of theCerealBox?3Experiment3Cathode Ray Tubes, Millikan Oil Drop, and Avogadro’s Number5Experiment4Conservation of Mass and Reaction Types–Copper Recovery Cycle8Experiment5Equivalent Weights and the Periodic Table10Experiment6Hydrates12Experiment7Gas Laws14Experiment8Styrofoam Cup Calorimetry: Atomic Weights16Experiment9Chemiluminescence: GlowStick in aBeaker19Experiment10Atomic Spectra22Experiment11Reactivity ofGroup 1Metals–Yes, Mom, IThrewSodium inWater inClassToday23Experiment12Flame Tests–Flames and Smoke Bombs26Experiment13VSEPR and Molecular Models29Experiment14Simulating the Shroud of Turin: An Inquiry-based Experiment31Experiment15Taste Observe the rainbow: PaperChromatography34Experiment15BChemical Oil Dispersant Experiment36Experiment16Sublimation41Experiment17Closest Packed Structures43Experiment18Colligative Properties–FreezingPointDepression47Experiment19ADiet Coke and Mentos–An Inquiry-Based Experiment49Experiment19BKinetics: Testing forSemen–AcidPhosphatase51Experiment19CActivation Energy Determination54Experiment20EquilibriumConstants and LeChatelier’sPrinciple–CoCl256Experiment21Far from Equilibrium Systems: Creating Life in a Beaker61Experiment22Acid-baseTitration63Experiment23Determining theBufferCapacity ofAntacids65Experiment24Entropy–TheChelateEffect67Experiment25Redox Reactions–DetectingTraces ofBlood69Experiment26Radioactivity72Experiment27AGroup I Cations75Experiment27BGroup II Cations: “I love the smell of hydrogen sulfide–It smells like victory”77Experiment27CPiltdown Man and Scientific Ethics80Experiment27DGroup IV Cations83Experiment27EAnions85Experiment28Esters87Experiment29WhichCompoundsAreGenotoxic orCarcinogens?: CleavingPlasmidDNA andGelElectrophoresis89

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iiiPreface for InstructorsWhen one of the authors was in high school deciding what major he would be in college, hewas leaning toward chemistry. He favored chemistry over physics and mathematics because of whathe had performed in chemistry lab with his own hands. Somehow there was something more tomixing the chemicals together and getting precipitates, gas bubbles, or color changes than watching ablock slidedown an inclined plane. Getting into the lab and making something happen (i.e., blowingsomething up) or making something new is probably the inspiration for nearly all budding chemists.Chemistry isa “hands-on” science. How often do we say this toour studentsor toadministrators to justify the expense of the lab? Chemists inherently understand this to be true. Seeingsomething happen is more educational and powerful than only discussing the theory behind it. At afundamental level, chemistry occurs beyond the naked eye, beyond the grasp of most of our senses.One of the authors was fortunate in having an excellent laboratory experience in high school; he evengot to throw tiny pieces of sodium metal into a beaker, rapidly cover the beaker with a watch glass,and observe what happens, for example. When he talks to old high school companions who went intoother areas, they still remember this experiment.This is the kind of excitement we are aiming for in this laboratory manual project. We wantstudents to see things for themselves and do things for themselvesthatwill emphasize the conceptsfrom the lecture portion of general chemistry. Most laboratory manuals seem to be a tired rehashingof the same material–all but interchangeable. The authors often seem to forget to ask whether theexperiment would have been fun or exciting if they were a student. Thus, one finds dry “cookbook”laboratory manuals. The “cookbook” label is somewhat unfair as no matter what type of laboratoryexperiment is being performed (even an inquiry-based experiment), the students must be guidedthrough the exercise. A novice observer cannot be expected to necessarily make the importantobservations without training into what is important to look for.With this in mind, we are attempting to devise a laboratory manualthatis concept oriented,has varying levels of student guidancerangingfrom what is now called “inquiry-based” to classical“cookbook” and hands-on and exciting. Why should the professor in front of the class be the only oneto perform the exciting chemistry of the lecture demonstrations? Why not have students throw sodiuminto water, make things glow in the dark, and mix chemicals together to get results they never couldanticipate (as in an oscillating reaction)? We also believe that some issues not normally treated inthelaboratory to an appreciable degree can be covered such as the scientific method and scientific ethics.All this can be handled, we believe, without straying too far from familiar territory to thoseindividuals who must be in the trenches setting up experiments, teaching the lab, or directing graduateassistants. Thus, a variety of techniques to approach “traditional” experiments will be presented tostudents. Some are open ended. Some are inquiry driven. Some are driven by attempting to obtain ananswerclosetoanacceptedstandard.Somearebasedoncurrentevents,someoncurrent“sensational” entertainment, and some on history. Through it all, our aim is to present concrete andgraspable theories with experiment and example.We are including qualitative analysis in this manual. We believe the logic structure of thisprocess, including using flow diagrams,is an important contribution to the course.

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ivWhen we set out to write this manual,our intention was to have detailed waste-disposalprocedures. As we looked into this issue, we found that local regulations and restrictions were sovaried as to make this impractical. We have made notes of when items require particular care,regardless of location. Please work with your chemical hygiene officer to work out the properconditions for your location.We hope you and your students can have fun and learn from what follows. In addition, pleasefeel free to send us your comments or those of your colleagues and students. We appreciate any inputso that we can continuously improve this manual.John B. Vincent and Erica Livingston

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vGeneral Laboratory and Safety RulesFor the InstructorThe general laboratory and safety rules are only intended to provide basics common to all generalchemistry laboratories; they are not meant to be comprehensive or to cover the specialized needs ofany particular laboratory situation and environment. Each instructor should provide details and editthe rules as necessary to their own situation. Instructors should acquaint themselves with morecomprehensive laboratory safety publications such asSafety in Academic Chemistry Laboratoriespublished by the American Chemical Society.11.American Chemical Society Committee on Chemical Safety.Safety in Academic ChemistryLaboratories, 7thed. American Chemical Society: Washington, DC, 2003.

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viName__________________________________________________ Student No:_______________________Room & Day _____________________Desk Number ________ Course & Section ____________________ReceivedReceivedInFromInFromDrawer StockroomPriceDrawer StockroomPrice__________1 Beaker, 50ml$3.23__________1 Litmus paper, red$0.77__________1 Beaker, 100ml$4.35__________1 Litmus paper, blue$0.77__________1 Beaker, 250ml$4.20__________1 Pipet,serological (measuring)10ml$10.60__________1 Beaker, 400ml$3.75__________6 Pipets, dropping, w/bulb$0.45__________1 Beaker, 600ml$6.18__________1 Spatula, scraper$9.10__________1 Bottle, Nalgene 250ml$1.73__________1 Sponge$1.84__________1 Bottle, Nalgene, 500ml$2.67__________6 Stirring rods, 6″$1.66__________1 Bottle, wash, 250ml$4.14__________1 Stopper, #4, 1-hole, split$0.78__________1 Brush, test tube, 8″$2.66__________1 Support, test tube$10.90__________1 Brush, test tube, 10 1/2″$4.40__________12 Test tubes, 10mm×75mm(3″)$0.44__________1 Bulb,30ml, rubber$15.81__________6 Test tubes, 16mm×150mm(6″)$0.63__________1 Clamp,pinch$4.58__________2 Test tubes, 25mm×200mm(8″)$1.21__________1 Clamp, test tube$5.80__________1 Wire gauze, 6″×6″ceramic$1.68__________1 Cylinder, graduated, 10ml$10.01__________1 Clay triangle$1.98__________1 Cylinder, graduated,100ml$16.03__________1 Tongs, nickel-plated$15.46__________1 Flask, Erlenmeyer,125ml$4.69__________2 Watch glasses, 50mm$4.05__________1 Flask, Erlenmeyer,250ml$4.69__________1 Stir bar$3.55__________1 Funnel, glass, 65mm lg$9.76__________1 Thermometer$17.51Lost or broken items should be replaced promptly.The above items were received in good condition, as verified by signature below. I understand that these items aresolely my responsibility and that I must return everything I receive, also in good condition.Checked-in by____________________________________________Date checked-in__________________________Student SignatureTA Signature _____________________________________________Date __________________________

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viiInstructor’s Equipment ListLarge EquipmentCathode ray tube with power supply1 per groupCapacitor setup (if not included with cathode ray tube)1 per groupCommercial apparatusforMillikan oil drop1 per groupSpectroscope1 per groupHydrogen lamp1 per groupMercury-vapor lamp1 per groupPower supply for lamp1 per groupSpectrometers1 per groupCentrifuges (addition test tubes)1 per groupOven with insulated gloves4-5 per roomGeiger counter1 per groupRingstands with ring and clamp1 per studentBalances4-5 per roomBunsen burners with lighter1 per studentMagnetic stirrer/hot plate1 per 2-4 studentspH meter and buffers1 per 3-5 studentsGel electrophoresis apparatus1 per groupHot plate/stirrers1 per groupUV transilluminator and cameraSection Equipment50 mL buret1 per studentBuret clamp1 per studentFilter flask1 or more per groupBuchnerfunnels1 or more per groupPorcelain crucible and cover1 per studentShooting mechanism1 per groupCompass or string1 per group10-15 mL plastic centrifuge tube with cap1 per groupBar magnet4-5 per roomCrystallization dish1 per studentRuler (in cm)1 per student1000-mL or larger beaker1 per group3-L or larger graduated cylinder1 per section2-L or larger graduated cylinder1 per section100-mL graduated cylinder1 per group25-mL graduated cylinder1 per student or group20-L or larger bucket1-2 per section40 feet tygon tubing–¼ inch diameter1-2 per sectionStopper (size 000)1-2 per sectionMeter stick or tape measurer1 per group#9 rubber stopper1 per group

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viiiStyrofoam cup2 per studentLid for cup (with hole for thermometer)*1 per student500-mL Erlenmeyer flask2 per student or group125-mL Erlenmeyer flask6 per groupBackdrop material (aluminum foil, etc.)Spray bottles5-6 per sectionMolecular model kit1 per studentPaint brushes1 per groupPlastic baby doll1 per groupHeat gun1-2 per groupCotton broad cloth1-2 yards per groupKnife1 or more5-6 all-purpose lighters (Aim-N-Flame)Crystallization dish800 mL or 1 L beaker1 per studentPencilBlack light (optional)Scissors1-mL pipet1 per student2-mL pipet1 per student5-mL pipet1 per studentCuvette (if required for spectrometer)1 per studentWhite cloth cut into squares1 yard per classAlpha, beta, and gamma sources1 per groupPiece of paper1 per groupPiece of wood, ~1/4 inch thick1 per groupSheet of lead, ~1mm thick1 per groupThicker piece of lead1 per groupCobalt (blue) glass plates>2 per roomStopwatch or timer4-5 per roomPlexiglass box 13″×13″×13″1 per groupStyrofoam balls 2 3/8″>23 per groupTarget marbles>60 per groupJumbo marbles>60 per groupPlay balls2.4′or 60 mm>90 per groupConsumable materialsFilter paperFood coloringMarking penWeight boats (capable of holding 8 mL water)Boiling chipsLaboratory soap9″Pasteur pipetPasteur pipet bulbBalloons (7″round)

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ixRubber bandsTooth picks (plastic, round)Plastic wrap (parafilm or aluminum foil)Tape or staples/staplerNichrome wireCandy piecesChalkInkMeat drippingsDiet Coke (2 L bottles)MentospUC19 plasmid DNA solution1 mL or similar-size microcentrifuge tubesAlka Seltzer tabletsIceTap waterInstructor’s Chemical List (note for section of 24 students)3,3’,5,5’-tetramethylbenzidine solution<100 mL4-(2-pyridylazo)resorcinol, monosodium salt hydrate<0.1 g9,10-Bis(phenylethynyl)anthracene0.12 g9,10-Diphenylanthracene0.12 gAcetic acid30 mLAcetone1.0 LAgerose (gel quality)10 gAluminum foil3 rollsAluminum hydroxide5 gAmmonia-based cleaning solution or 6M NH4OH~1 LAmmonium acetate80 mLAmmonium carbonate monohydrate6.0 gAmmonium hydroxide<3 LAmmonium oxalate<50 mLAmmonium sulfate<50 mLAscorbic acid10 gBarium chloride30 mLBariumnitrate5 gBenzene300 mLBenzyl alcohol<100 mLBromophenol blue<20 mLButyric acid<200 mLCadmium~1 kgCalcium chloride30 mLCalcium sulfate30 mL

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xChloroform500 mLChromium~1 kgChromium chloride hexahydrate<30 gCobalt chloride hexahydrate<50 gConcentratedHydrochloric acid1-2 LConcentratedNitric acid1-2 LConcentrated (NH4)2Sx80 mLConcentrated Sulfuric acid1-2 LCopper (II) chloride50.0 gCopper sulfate pentahydrate<30 gCopper wire12 gCorn starch~50 gDichloromethane<3 LDiethylenetriamine<1 LEthanol2 LEthidium bromide<0.1gEthylenediamine<1 LEDTA1 gFD&C #2, indigo carmine5 mgFD&C Red #40<0.1 gFerric oxide powder~500 gFluorescein1.2 gFormic acid<100 mLGlacial acetic acid50 mLGlycerin< 10 mLHexanol<100 mLHydrogen peroxide<200 mLIron~1 kgIron (III) nitrate (prepare fresh)30 mLIron filings<10 gIron fillings2.500 gIronsulfate (prepare fresh)5 gIsoamyl alcohol<100 mLIsobutyl alcohol<100 mLKHP (potassium hydrogen phthalate)50 gLemon juice~500 mLLeucomalachite green solution<100 mLLithium chloride10.0 gLithium metal5 gLithium nitrate5 gLuminol (3-aminophthalhydrazine)2.4 g

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xiMagnesium chloride5 gMagnesium hydroxide5 gMagnesium sulfate25 gMalonic acid100 gManganese~1 kgMercurous chloride<5 mLMethanol7 LMethyl red<0.1 gMethyl salicylate<5 mLMethyl violet in dropper bottle20 mLMethylene chloride30 mLNaphthalene<300 gNickle sulfate septahydrate70 gOctanol<100 mLOleic acid0.02 gOxalyl chloride in dichloromethane<100 mLParanitrophenyl phosphate, disodium salt hexahydrate25 mLpara-dichlorobenzene25 gPicolinic acid1 gPhenolphthalein1 LPotassium bromate100 gPotassium chloride5 gPotassium dichromate<10 mLPotassium ferrocyanide<10 mLPotassium metal5 gPotassium nitrate300 gPotassium permanganate30 mLPotassium thiocyanate<15 mLPropanol<100 mLPropionic acid<100 mLProstatic acid phosphatase (bovine)25 mLRed #400.125 gRhodamine B1.2 gSalicylic acid50 gSaturatedbarium hydroxide<50 mLSaturated Msilver nitrate<125 mLSilver sulfate<10 gSodium acetate<2 gSodium bicarbonate300 gSodium bismuthate15 gSodium carbonate48.0 g

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xiiSodium citrate5 gSodium chloride50.0 gSodium hydrogen carbonate5 gSodium hydrogen phosphate<5 mLSodium hydroxide5-6 LSodium hypochlorite30 mLSodium metal5 gSodium nitrate5 gStearic acid5 gStrontium chloride10 gSucrose10 gThioacetamide410 gTin10 gTin chloride~1 kgTRIS-acetate1 gXylene cyanol FF1 gZinc2.5 gZinc oxide~1 kg

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1Experiment 1LaboratoryBasics: Accuracy andPrecision–Who’s theShootingChampion?For the InstructorThis lab is designed to add fun and excitement to the traditional first experiment in the first-semestergeneralchemistrylaboratory.Forshootingatatarget,wewouldrecommendbeingopentoexperimentation. A large catapult throwing water balloons at a large target such as a sheet paintedwith a bull’s eye, a paint ball gun and target, blunt-tipped arrows shot into a target mounted on a thinpiece of styrofoam, throwing horseshoes, rolling balls into a bull’s eye, throwing small bean bags(as in tail gate toss) at a target, chipping golf balls at a flag, or even just darts and a dart board can beconsidered. A safe indoor alternative is foam dart guns; these darts can be fired at a target drawn on adry erase board or chalk board. Cost is only around $10, and they can be found at most toy stores.Moistening the end of the suction cups helps the dart to adhere to the target.In our experience, 10 mL disposable plastic centrifuge tubes are surprisingly accurate, just as accuratewithin error as 10 mL graduated cylinders. However, because the tubes have fewer graduations,estimating the last significant figure when adding a given mass of water is more difficult. We havealso found that the reproducibility of measuring 8 mL of water is greater with the plastic tubescompared to the graduated cylinder as it is easier in the plastic to gently tape the container to removeair bubbles and water droplets clinging to the side.Preparation Information–24 studentsShooting mechanism (refer to previous discussion)1 per groupCompass or string10-or 15-mLplastic centrifuge tube with cap1 per groupWeight boats (capable of holding 8 mL water)1 per groupNecessary Equipment–24 studentsPaper towelsDisposable glovesBalance4 or 5 per room10-mL graduated cylinder1 per group

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Experiment 1: Laboratory Basics: Accuracy and Precision–Who’s the Shooting Champion?2Answers toPre-Laboratory Questions1.William Tell had only one shot to shoot an apple from the top of his son’s head with his bow andarrow. If you were William Tell and you loved your son, would you rather be accurate or precise?Explain why.Accurate–hit the apple. Precise refers to reproducibility, which is not applicable with one shot.2.Assume that you found that the average volume of water required to fill the graduated cylinder tothe 8.00 mL mark was 7.95 mL. Calculate the % error.(7.95 mL−8.00 mL)/8.00 mL×100% = 6%

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3Experiment 2Components of a Mixture–WhatIsThatStuff in theBottom of theCerealBox?For the InstructorThe mixture per student should contain approximately 5 mg red #40, 100 mg Fe, 100 mg ZnO,200 mg stearic acid, and 395 mg sucrose per gram. If the sucrose crystals are large, theymighttake aconsiderable time to dissolve,and grinding the sucrose before making the mixture is advisable.The concentration of the methanol solution from 200 to 5-10 mL will take longer than a single labperiod.This process can be facilitated by placing in a well-ventilated hood.During the followingweek, someone will need to check these and move them to a freezer at the appropriate time. Verylittle time will be required during the next laboratory period to complete the experiment.This experiment can be performed much faster if gravity filtration is replaced with the use of aBuchner funnel, filter flask, and vacuum source.Preparation Information–24 studentsMethanol~6 LChloroform<500 mL(mixture–25 g)~25g per sectionIron fillings2.500 gramsZinc oxide2.500 gramsSucrose9.875 gramsRed #400.125 gramsStearic acid5.000 gramsNecessary Equipment–24 studentsPaper towelsDisposable glovesFilter paperWeigh boats/weighing paperFunnel1 per studentBeaker (20 mL)2 per studentBeaker(400 mL)2 per student10-mL graduated cylinder1 per student (optional)100-mL graduated cylinder1 per student (optional)Ring stand1 per studentIron ring1 per student

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Experiment 2: Components of a Mixture–What Is That Stuff in the Bottom of the Cereal Box?4Clay triangle1 per studentStirring rod1 per studentWash bottle2 per 1-4 studentsSpatula1 per studentBar magnet1 per 1-4 studentsRubber policeman1 per studentMagnetic stirrer/hot plate1 per 2-4 students (optional)Balance4-5 per roomAnswers to Pre-Laboratory Questions1.How could you determine (without tasting) whether a container of a colorless liquid containedethanol or ethanol and sucrose?Allow the ethanol to evaporate;a white crystallinesolid left would indicate the presence ofsucrose.2.Does this experiment demonstrate the law of conservation of matter?No. No chemical reactions are involved, only physical separations.3.Explain the difference between filtration and decantation (see the “ExperimentEquipment andProcedures” section of this manual). Why might one want to use filtration in this experimentrather than decantation?Decanting works if solid(s) stay at the bottom of the container. If they are likely to be disturbed,then filtration should be used.4.How could one rapidly separate red #40 from zinc oxide? Indicate every step.Add water and agitate to dissolve the red #40. Filter and wash the solid with water. Solidremaining is zinc oxide.5.Separation techniques are performed on a sample containing sand and salt. It was determined thattherewere5.43 g of sand and 4.52 g of salt. The total sample weight was 10.50 g. What is thepercent recovery of sand from the sample?(5.43 g + 4.52 g)/10.50 g100% = 94.8%

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5Experiment 3Cathode Ray Tubes, Millikan Oil Drop, and Avogadro’s NumberFor the InstructorWe believe it is very important that students actually measure a fundamental constant or anotherimportant number used in general chemistry lectures. Given the emphasis placed on the charge on anelectroninmostgeneralchemistrytextbooks,thisisourfundamentalconstantofchoice.Unfortunately, this determination cannot be performed with normal general chemistry laboratoryequipment; in fact,the equipment is rather expensive compared to most general chemistry equipment.If we had ideal conditions and budgets, we would have students measure the charge to mass ratio onan electron using a commercial system sold by Pasco (www.pasco.com) and then use a commercialsystem to perform the Millikan oil drop experiment (also sold by Pasco and other companies);however, the apparatuses cost $1,500to$2,500.Students can more affordably look at the behavior of electrons in cathode ray tubes ($500-$1,000 fora commercial setup and power supply, available from many science education equipment suppliers).We particularly like the cathode ray tubes with electrodes for applying a magnetic field built in (at thetime of writing, ~$250 from Sci-Supply plus the cost of a power supply). An alternative is to use anoscilloscope, as it contains a cathode ray tube. Instructors may already possess one in their departmentor be able to borrow one from their institution’s electrician or physics department. In addition todeflecting the path of the electrons of a cathode ray tube with magnets, the path can be altered byapplying an electric field with a capacitor (if one is not built into the unit); these are also available(<$500 plus power supply) from many science education equipment suppliers. This again is not aninsignificant cost, while one might be able to borrow these from a neighboring physics department.Fortunately, obtaining a reasonable value for Avogadro’s number can be accomplished cheaply andeasily in a time-tested experiment. This can also be performed as a demonstration by placing thewatch glass on an overhead projector.To form a monolayer requires only a few drops of the oleic acid solution. If students use more than 20drops, they are probably forming multiple layers.Also, in our experience, students should be walkedthrough the calculations in a lecture.

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Experiment 3:Cathode Ray Tubes, Millikan Oil Drop, and Avogadro’s Number6Cathode ray tubePreparation Information–24 studentsCathode ray tube with power supply1 per groupBar magnets>1 per groupCapacitor setup (if not included with cathode ray tube)1 per groupMillikan oil dropPreparation Information–24 studentsCommercial apparatus1 per groupAvogadro’s Number(24 students)Benzene is a possible carcinogen. Benzene-containing solution must not be disposed of down thedrain. The oleic acid/benzene solution should have a concentration of 0.02 g oleic acid per L solution.The methyl violet solution should be about 0.5%. A class of 24 should need ~0.5 L of oleicacid/benzene solution, <250 mL benezene, and <20 mL of 0.5% methyl violet solution per class of 24.Placing the ammonia-based cleaning solution in a wash bottle for students to use is recommended; theglassware is easier to clean in this manner, while the students use less of the solution.A pipetter thatdispenses a volume of 10L could be usedto replace the Pasteur pipet and calibrationprocess.Preparation Information–24 studentsOleic acid0.02 g for solutionBenzene300 mLMethyl violet solution in dropping bottle20 mLAmmonia-based cleaning solution or 6 M NH4OH~1 LDeionized or distilled waterLaboratory soapNecessary Equipment–24 students9″Pasteur pipet2per studentPasteur pipet bulb1 per student4-inch watchglass1 pert studentDropping bottle1 per class10 mL beaker1 perstudent5-or 10-mL graduated cylinderor 1-mL volumetric tube1 per studentRuler (in cm)1 per 4-6 studentsPaper towelsDisposable gloves

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Experiment 3:Cathode Ray Tubes, Millikan Oil Drop, and Avogadro’s Number7Answers to Pre-Laboratory Questions1.Oleic acid is a fatty acid and is essentially immiscible (insoluble in water). Given this, why do youthink that the glass surfaces in this experiment must be cleaned so carefully?Oleic acid may interact and stick to oil residue on glass surface rather than form layer on top ofwater.2.Find a material safety data sheet (MSDS) for benzene on the Internet. What are thehazardsassociated with working with benzene? What precautions should be taken?AGooglesearchof“MSDSbenzene”willprovidemanyexamples.Hazardsincludecarcinogenic, possibly mutagenic, and developmental toxins. Wear splash goggles, lab coat, andgloves.

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8Experiment 4Conservation of Mass and Reaction Types–Copper Recovery CycleFor the InstructorThis is a very conventional experiment, found in many laboratory books. This is because it isstraightforward and directly illustrates concepts from the textbook. In other words, it works andillustrates concepts well; thus, students like it, and therefore we like it.Students should be warned about handing strong acids (HNO3and H2SO4) and bases (NaOH).Copper-containing solutions (as with all solutions containing transition metals) should not be disposedof down the sink.This labcan belonger than the normal 2½-to 3-hour laboratory session, although we have had thestudents complete the experiment in 2½ hours.The experiment may be stopped after any of the steps.The solutions or solids need only be covered and saved until the next session.If the necessaryequipment is available, time can be saved by having the students use two filtration setups.Preparation Information–24 studentsAluminum foilCopper wire12 g (0.5 g per student)Conc. Nitric Acid240 mLConc. Hydrochloric Acid24 mL3.0 M NaOH1 L6 M Sulfuric Acid360 mLMethanol120 mLAcetone120 mLNecessary Equipment–24 studentsPaper towelsDisposable glovesRed Litmus paperBoiling chips2-3 per studentFilter paperWeigh boats or weighing paperBunsen burner1 per studentEvaporating dish1 per studentWire triangle1 per studentFunnel1 per student10-mL graduated cylinder1 per student100-mL graduated cylinder1 per student250-mL Erlenmeyer flask2 per student250-mL beaker2 per student

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Experiment 4: Conservation of Mass and Reaction Types–Copper Recovery Cycle9Beaker to use with evaporating dish to make steam bathStirring rod1 per studentRing stand and iron ring1 per studentWire gauze1 set per studentRubber policeman1 per studentHot plates (optional)1 per studentBalance4 or 5 per roomAnswers to Pre-Laboratory Questions1.List the hazards involved in this experiment. What can you do to minimize the chances ofanything bad happening in each case?Sulfuric acid and nitric acid are strong acids, while sodium hydroxide is a strong base. Becareful and wear gloves and goggles; lab coats are a good suggestion. Immediately wash anyskin or clothing that comes in contact. Wash surfaces that come in contact so that someone elseis not exposed accidentally. Have appropriate spill kits nearby.2.Name the gas produced when nitric acid is added to copper metal.Nitrogen dioxide3.During your experiment, you use 0.597 g of copper to start your reaction. After you carry throughall the different steps, you recover 0.684 g of copper. What is the percent recovery of copper?Since it appears that you may have created matter (which is not possible in this experiment), whatcould be a source of error?(0.597 g–0.684 g)/0.597 g100% = 146%. Solid not properly dried is most obviouspossibility.4.Identify the reaction types in equations 1,2, 4, and 5. Indicate why you made these choices(e.g., indicate gaseous products, precipitates, etc.).Eqn. 1–gas forming–NO2(g). Also redox–Cu0→Cu2+; N+5→N+4Eqn. 2–precipitation–Cu(OH)2(s)Eqn. 4–acid base–O2−+ 2H+→H2OEqn. 5–redox–Cu2+→Cu0; Al0→Al3+

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10Experiment 5Equivalent Weights and the Periodic TableFor the InstructorStudents should be instructed about the concerns associated with the use of corrosive materials.Students may desire to wear gloves. The aqueous solutions resulting from filteringandwashing theunreacted metals are not suitable to be poured down the drain. The solution for each metal should beplaced in a separate labeled waste container.Helium quality balloons should be used.The quality of the balloons used isimportant. If heliumquality balloons are not used, the highest quality available should be used. If lower quality balloonsare used, then the time used to collect the hydrogen gas should be minimized to prevent gas loss.This experiment is best performed over three weeks. At the end of lab 4 (or whatever lab is performedbefore this one), students should go ahead and label everything, weigh out the metal samples, and placethem into the appropriate balloons. This way the next week the acid can be placed in the tubes and themetal added early in the lab period to maximize the time for Fe, Mn, and Cr to react with the acid. Thethird week the Cd, Zn, and Sn portion can be completed. If the reactions with Zn, Cd, and Zn go tocompletion well before the third laboratory period, someone should measure the volume of theballoons promptly.This is preferably done after one day.If necessary, the reactions can be terminatedat the same time as those of Fe, Mn, and Cr; the volume and mass changes will just be small.The results of this experiment are designed to be used in conjunction with those of experiment 8.Preparation Information–24 studentsManganese24 gChromium24 gIron24 gZinc24 gCadmium36 gTin36 gConcentrated hydrochloric acid300 mLEthanol500 mLNecessary Equipment–24 studentsWeigh boatsPaper towelsMarking penFilter paper1000-mL or larger beaker1 per groupTest tubes (15 mm×150 mm)6 per group

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Experiment 5: Equivalent Weights and the Periodic Table11Balloons (7″round)7 per groupTest-tube rack1 per groupRubber bandsup to 6 per groupFilter flask1 or more per groupBuchner Funnels1 or more per groupWash bottle2 per groupSpatula1 or more per groupTest-tube holder1 or more per groupHot plate1 per group3 L or larger graduated cylinder1 per lab sectionBalances4-5 per roomAnswers to Pre-Laboratory Questions1.What is the valence for the six metals based on their reaction with hydrochloric acid?Cr−3Mn−2Fe−2Zn−2Cd−2Sn−22.How are atomic weights determined experimentally at the current time?Mass spectrometryis themost obvious answer from freshmantextbooks.3.What safety precautions are necessary in this experiment?Hydrochloric acid is a strong acid. Be careful and wear gloves and goggles; lab coats are a goodsuggestion. Immediately wash any skin or clothing that comes in contact. Wash surfaces thatcome in contact so that someone else is not exposed accidentally. Have appropriate spill kitnearby.

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12Experiment 6HydratesFor the InstructorConcentrated nitric acid (~15 M) should be carefully diluted in 2.5 fold to give ~6 M HNO3.Preparation Information−24 studentsCoCl2·6H2O<30 gCuSO4·5H2O<30 gCrCl3·6H2O<30 g6 M nitric acid<2 LNecessary Equipment–24 studentsPaper towelsDisposable glovesLarge beaker for acid bath1 or more per classPorcelain crucible and cover1 per studentCrucible tongs1 per studentRing stand with ring1 per studentClay triangle1 per studentPasteur pipet and bulb or dropper1 per studentBlue litmus paper1 piece per studentBunsen burner1 per studentLighter for burner1 per 1-4 studentsAnalytical balance (4 decimal places)4-5 per roomAnswers to Pre-Laboratory Questions1.If a hydrate of the formula MCly·xH2O decomposes when heated to produce HCl, what changewould you expect to occur when a piece of blue litmus paper is held in the path of the vaporreleased? Explain.The blue litmus paper should turn red as blue litmus paper turns red in the presence of acid andHCl is hydrochloric acid.

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Experiment 6: Hydrates132.After 0.6523 g of CoCl2·6H2O is heated, the residue has a mass of 0.3423 g. Calculate the % H2Oin the hydrate. What is the formula of the hydrate?0.6523 g total−0.3423 g CoCl2= 0.3100 g H2O0.3100 g H2O/0.6523 g total×100% = 47.52 % H2O0.3100 g H2O/18.02 g·mol−1= 0.01720 mol H2O0.3423 g CoCl2/129.83 g·mol−1= 0.002637 mol CoCl20.01720 mol H2O/0.002637 mol CoCl2= 6.523Formulais approx. CoCl2·6.5 H2O3.What safety precautions are necessary in this experiment?Nitric acid is a strong acid. Be careful and wear gloves and goggles; lab coats are a goodsuggestion. Immediately wash any skin or clothing that comes in contact. Wash surfaces thatcome in contact so that someone else is not exposed accidentally. Have appropriate spill kitnearby.4.CoCl2is often used in hygrometers. Search the Internet to determine why. How does this relate tothis experiment?Hygrometer indicates relative humidity,CoCl2is blue. As it picks up water, it forms CoCl2·6H2O which is pink.See,for example,http://wow.osu.edu/experiments/weather/humiditymonitor.html.

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14Experiment 7Gas LawsFor the InstructorNote that you will need to find an appropriate space in your facility (balcony, stairwell, etc.) whereone can make a measurement at the appropriate height (between 30 and 40 feet).The tygon tubing canbe sealed at one end by plugging with a rubber stopper.We have used filling the tubing as an inquiry-based exercise; thus, the procedure for thisexperimentis not spelled out in the lab procedure for thestudents.Many groups independently find our best solution–a pipet bulb can be used to set up asiphon, pulling water from the bucket through the tubing, followed by sealing the end quickly.Thefilled tubing should be kept in the bucket to prevent air from getting in until the barometer reading isattempted.The local barometric pressure can be obtained from any number of sources.For example,aconvenient source iswww.weatherchannel.com; just enter a zip code.For the second part of the experiment, we have found that driving a nail halfway through the #9rubber stopper and then removing it makes a hole suitable to insert the syringe and get an excellentseal.The holes should be made in advance, not by the students in the lab, to avoid getting smashedfingers.The syringe should have a Luer-slip tip.Necessary Equipment–24 student20-L or larger bucket1-240 feet tygon tubing–¼ inch diameter1-2Stopper (size 000)1-2Food coloringMeter stick or tape measurer1 per groupPipet bulb1 per groupRing stand1 per groupClamp1 per group50-mL plastic syringe1 per group#9 rubber stopper1 per groupGlycerinTextbooks4 per groupBalance (capable of measuring kg quantities)1

Solution Manual for Chemistry A Molecular Approach, 4th Edition - Page 28 preview image

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Experiment 7: Gas Laws15Answers to Pre-Laboratory Questions1.Look up the atmospheric (or barometric pressure) in your area in the newspaper, on television, oranother news outlet.Whatarethe units used?Convert to mm Hg.Convert to mm H2O.30.07 inches Hg2.54 cm/in10 mm/cm = 762 mm Hg762 mm Hg13.5340 g·ml−1/0.99707 g·ml−1= 1.03104mm H2O2.Should atmospheric pressure increase or decrease as one goes from the beach to the mountains?Explain.Decrease, as less of the earth’s atmosphere above.3.If the column of water in the water barometer rose to a height of 35 feet, what would theatmospheric pressure be in mmHg?35 ft12 in/ft2.54 cm/in10 mm/cm = 1.1104mm water1.1104mm0.99707 g·ml−1/ 13.5340 g·ml−1= 8.1102mm Hg4.After you set up your apparatus for part twoof the experiment, your group begins to add thetextbooks to the plunger.It appears that the plunger continues to drop with every added book anddoes not return to its original place after the books are removed.What could be possible sourcesof error for thisexperimentalreaction?Be specific and give at least two possible reasons.1) Syringe is leaking–make sure firm seal with tip in stopper and piston in syringe2) Piston not sliding freely–lubricate as described.

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16Experiment 8Styrofoam Cup Calorimetry: Atomic WeightsFor the instructorThe results of this experiment are designed to be used in conjunction with those of experiment 5.Theexperiment can be performed individually; or to reduce time, samples of the metals can be dividedamong members of groups.Normally, individuals or groups can each only make measurements on atmostthreemetals in a single lab period.A paper towel, folded to make it thicker, can be placedaround the thermometer at the point where it is clamped to help keep the thermometer in place by theclamp; we find this preferable to a one-hole rubber stopper (as students often snap off thermometersattempting to insert them into rubber stoppers).The thermometer is clamped in place primarily tokeep it from tipping over the calorimeter.If a stirring bar is used, the thermometer should be placedoff center, leaving room for the stir bar to turn.Preparation Information–24 studentsThe mass of the metal pieces should be approximately 3-5 grams.Manganese~1 kgChromium~1 kgIron~1 kgZinc~1 kgCadmium~1 kgTin~1 kgNecessary Equipment–24 studentsWeigh boatsPaper towelsStyrofoam cup2 per personLid for cup (with hole for thermometer)*1 per personThermometer2 per personRing stand1 per personUtility clamp1 per personMetal wire or stirring bar1 per personMagnetic stirrer1 per person (optional)400-mL beaker1 per person250-mL beaker1 per personTongs1 per person100-mL graduated cylinder1 per personTest tube1 per personTest tube holder1 per personBalances4-5 per room*Asecond tiny hole will be needed if stirring is done with a piece of wire.

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Experiment 8: Styrofoam Cup Calorimetry: Atomic Weights17Answers to Pre-Laboratory Questions1.Find and report literature values for the specific heats of the metals used in this experiment atroom temperature.Cr–0.107 cal·g−1·K−1Mn–0.114Fe–0.106Zn–0.092Cd–0.0555Sn–0.053From Chemical Rubber Handbook2.Compare the specific heats of the metals with their atomic weights (i.e., molar masses).Do yousee any trends?Make a plot to show this relationship.What does the plot reveal?Inversely related.Slope is negative of constant ofEqn. 1.For this plot of these few metals, thevalue is ~8.7.Atomic Weight406080100120140specific heat0.040.050.060.070.080.090.100.110.12

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Experiment 8: Styrofoam Cup Calorimetry: Atomic Weights183.If you are performing the calibration step of this experiment and you begin with 50 g of water at20°C and 50 g of water at 80°C.After adding the two in your calorimeter setup and following theprocedure outlined in the experiment, you determine the temperature of the mixed solutions to be45°C.What is the heat capacity of the calorimeter?Use Eqn. 4 and assume room temperature is 25°C:-S.H.warm watermasswarm waterTwarmwater =S.H.cool water×masscool waterTcool water+ CcalorimeterTcalorimeter-1.00cal/g·K50 g(45°C−80°C) = 1.00 cal/g·K50 g(45°C−20°C) +Ccalorimeter(45°C−25°C)Ccalorimeter= 25 cal/K

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