Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition

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Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition - Page 1 preview image

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Experiment 1This may be a student’s first experience in the laboratory. Therefore, the instructor shoulddemonstrate all the techniques used in this laboratory. Show how a Bunsen burner is lit, with amatch or a gas striker, and how the flame is adjusted by control of the gas valve and air vents.This is a relatively simple laboratory for students to work. Most of the commonequipment used in the laboratory are introduced here. For many this might be the first time someof the glassware will be encountered. For the instructor, patience is in order since the lack offamiliarity of the student with the laboratory ware often creates problems. Take the graduatedcylinder, for example. Since it is tall, it is easily knocked over, and although laboratoryglassware is reasonably durable, it will shatter and could cause severe cuts. Remind students notto pick up broken glass with the fingers but to use the dustpan and brush. Broken glass should bediscarded in a waste container specifically for glass.While there is little danger in this laboratory of eye damage, nevertheless, it is essentialthat the rules of the laboratory be followed:safety glasses are to be worn at all times in thelaboratory.The thermometers in this laboratory are made of glass and must be handled properly. Athermometer is not a stirring rod and must not be used as such. If a student wants to bring thefluid level in the thermometer down, remind him/her to use cold water from the tap. Thelaboratory thermometer is not a clinical thermometer and does not require that it be shakendown! Waving the thermometer usually results in it hitting a bench top and breaking. Some ofthese thermometers contain mercury; the breakage of a thermometer with resultant spillage ofmercury must be cleaned up quickly. Mercury is toxic, especially as a vapor. The instructorshould be notified immediately for proper clean up. No mercury should be left freely aboutanywhere. Mercury can be collected with commercial collectors or by a homemade suctionapparatus. Connect a side-arm suction filter flask to a water aspirator. The flask is fitted with aone-hole rubber stopper with a small section of glass tubing inserted into the hole. Rubber tubingconnects the glass tube to a Pasteur pipet. When the water is turned on, the spheres of mercurywill be sucked into the pipet and then into the suction flask. The recovered mercury can be storedunder water.Balances should be handled with care; electronic top-loading balances are sensitive andlose calibration easily. Demonstrate proper use of the balance. Emphasize that no chemicalshould be weighed directly on the pan; use either weighing paper or a suitable container. Alsohot objects should not be put on the pan. Proper care requires that all weights be returned to zero.The difference between precision and accuracy can be easily demonstrated. Use twobalances, one that has been zeroed and calibrated, a second not zeroed and uncalibrated.Repeated weighings of the same object of known weight on the two balances will show highprecision (high reproducibility in the clustering of the weights) for each of the two balances butnot the same accuracy (agreement with the known weight).

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namesectiondatepartnergrade1EXPERIMENT1Pre-LabQuestions1. In thedesignof a Bunsenburner,explainthepurpose ofa.the gas controlvalveManipulation of this valve controls the flow of gasb.and the airvents.Manipulation of these vents controls the mixing of air with gas; allows the control of flame temperature.2. Why is aluminousyellow flame often‘‘smoky’’?Lack of sufficient air causes incomplete burning of the gas and produces soot.3. Astudent wanted20.000 g of a salt. Which balanceshouldthestudentuse in order to obtain themostaccurate quantity:aplatformtriple beam balance, a single pan, triple beam balance, or atop-loadingbalance?Explainyouranswer.The top-loading balance enables you to weigh to the nearest 0.001 g.4. Explainthedifference betweenprecision and accuracy?Precision determines the reproducibility of a measurement; accuracy is a measure of how closely the value determinedagrees with a known or accepted value.5. Solve thefollowing problemsandrecordtheanswersto theproper numberofsignificant figures.a.21.65 - 3.2= 18.5b.4.01 ÷ (4.583 + 2.108)= 0.599c.6.15 ÷ 1.2 = 5.1d.2.26 x 21.43= 48.42

Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition - Page 4 preview image

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namesectiondatepartnergrade1EXPERIMENT1Report SheetBunsen burner1.What is the color of the flamewhenthe air vents areclosed?Yellow2.Didanything happento the surface of the Pyrex test tube in thisflame?Soot collected on the test tube3.Whathappensto the flame sizewhenthe gas control valve isturned?The flame changes in size4.Describe the effect on the flame as the air vents wereopened.The flame looses the yellow color and becomes blueLength1. Length27.5cmWidth21.5cm2. Length275mm0.275mWidth215mm0.215m3. Area591cm2(Showcalculations)27.5 x 21.5= 591.25= 591275 x 215= 59125= 5910059100m3

Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition - Page 5 preview image

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Volume1.Erlenmeyerflask49.5mL0.0495L2.Beaker42.0mL0.0420L3.Errorinvolume:Erlenmeyerflask0.5mL1%%Beaker2.0mL5.0%%ErrorinvolumeTotalvolume%Error=x100(Showyourcalculations)(0.5/50) x 100=1%(2.0/40) x 100= 5.0%4.Graduated cylinderMassObjectBalancePlatformSinglePan,TripleBeamTopLoadinggmggmggmgQuarter5.858005.6156105.6135613Testtube(10013mm)8.181007.9279207.8727872125-mLErlenmeyerflask77.17710076.957695076.94876948Temperature8C8FKRoomtemperature22.572.5295.7Icewater0.532.9273.7Boilingwater99.5211.1372.7How well do yourthermometer readingsagree with theacceptedvalues for the freezingpointandboiling point of water?Express anydiscrepancyas adeviationindegrees.Freezing Point: + 0.5 degrees CelsiusBoiling Point: -0.5 degrees Celsius4

Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition - Page 6 preview image

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Post-LabQuestions1.How does astudentneed to adjustthe Bunsenburnerin orderto changealuminousyellowflameinto anonluminousblueflame?Open the air vents at the bottom of the burner barrel; more air assures complete combustion.2.What causes theluminescencein the cooler, yellowflame?Unburned small particles of carbon, soot, causes the luminescence.3. Astudent neededexactly 45.3 mL of asolution.What piece ofglassware shouldthatstudent use?Justify yourchoice.The graduated cylinder has gradations in 0.1 mL and would give the more accurate measure.3.Thediagrambelow is of anonluminousBunsen flame.Indicatetheapproximateregion of thehottestpart of theflame.The tip of the inner blue cone is the hottest part of the flame.5. Twostudents weigheda 125-mL beakerthathadamassof 80.562 g on acalibrated top-loadingbalance.Eachstudentusedtheirowntop-loadingbalance,recordedthreemass readingsfor thebeaker,andthendeterminedtheaverage.Below are theresults:StudentAStudentB80.56080.40080.55579.55180.56581.729Average:80.56080.560a.Find theaverages.b.Which set ofresults matchestheknown massof thebeaker?Both sets agree well with the known weight of the beaker.c.Which set ofresultsis moreprecise?Student A has a balance that gives more precise results; the weights are more reproducibled.Whichstudenthas the more reliablebalance?Student A has a more reliable balance5

Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition - Page 7 preview image

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6. Astudent measuredthedimensionsof a table andrecordedthe lengthas 103.50 cm and thewidthas 73.75 cm.Accordingto thestudent’scalculator,the area is 7633.125 cm2. Whatshouldthestudentreport?Explainyouranswer.The answer is good to only 4 significant figures. The answer is 7633 cm square.7. Johnhas a mass of115 kg. Sallyhas a mass of115 lb. Who is theheavierof the two?Showyourcalculations tojustify youranswer.115 kg x 2.20 lb/kg=253lb.John is heavier8. At 20,320 ft., MountMcKinleyin Alaskais thehighestpeakinNorthAmerica.Expresstheheightinmeters(m) andkilometers(km) to the correctnumberofsignificantfigures.Show yourwork.20,320 ft x 30.48 cm/ft x 1 m/100 cm x 1 km/100m = 6.194 km20,320 ft x 30.48 cm/ft x 1 m/100 cm = 6194 m9. A 16.95 gsampleofsugarwasaddedto a glasswith a mass of8.3 oz. What is thecombinedmassoftheglassandthesamplein ounces(oz.), grams(g), andmilligrams(mg)? Show yourwork andexpressyouranswersto the correctnumberofsignificant figures.8.3 oz. x 28.35 g/oz. = 235.3 g or 240 g to 2 sig. fig.16.95 g + 235.3 g= 252.3 g or 16.95g +240 g= 257 g if you follow sig. fig. rules257 g x 1000 mg/g= 257,000 mg16.95 g x 1 oz./28.35g= 0.5979 oz.8.3 oz. + 0.5979 oz. = 8.8979 oz. = 8.9 oz. to 2 sig. fig.6

Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition - Page 8 preview image

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Experiment 2This laboratory provides a bit of fun for the student; the student will use the experimentin the locker to solve a puzzle. Each will be given unknowns of various kinds and asked to findout the identities by taking suitable measurements. Thus, using precision, accuracy, andsignificant figures in their measurements, each unknown can be identified. (Eureka!)In the use of balances, again remind students not to weigh directly on the pan, but to use acontainer or weighing paper. In the case of the unknown metal, provide suitable containers fortheir recovery. For the other unknowns, waste containers should be provided. Nothing should bediscarded into the sink.Reading the volume in a graduated cylinder requires lining up of the eye with themeniscus. Demonstrate the proper technique for doing this. It may be the student’s firstencounter with the Spectroline pipet filler. It would be best to go through the way it works,particularly in the suction phase of its use. If the tip of the pipet is not immersed far enough intothe liquid to be pipetted, the force of the suction might cause the liquid to be drawn up into theSpectroline pipet filler’s body; these liquids will cause the inside to deteriorate. In addition, theliquids in the pipet filler will contaminate the next liquid to be pipetted, and so this situationshould be avoided.

Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition - Page 9 preview image

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namesectiondatepartnergrade2EXPERIMENT2Pre-LabQuestions1.Howdoesan intensive propertydiffer from an extensive property?Give an example of anintensiveproperty and of an extensiveproperty.The intensive property does not depend on the quantity of the substance: density.An extensive properly depends on the quantity of the substance: mass.2.In order tocalculatethedensityof a solid orliquid sample,whatmeasurementsareneeded?You need a mass measurement and a volume measurement.3. Thevolumeof a fixed mass of aliquid sample increasesas thetemperaturerises from 20to408C.Does thedensityincrease,decrease,or stay the same? Explainyouranswer.As the temperature rises, there is a change in the volume, the volume gets larger. As a result,the density will decrease. (mass/volume= density) Remember, there is no change in the mass;the only factor changing is the volume (you are dividing by a bigger number as the volumeincreases with increasing temperature).4.A solid block of exactly 100.0 cm3has a mass of 153.6 g.Determineitsdensity.Will theblocksink orfloat onwater?153.6g/100.0 cc = 1.53 g/cc. This density is greater than the density of water, so it will sink.5. A salvageoperator recoveredcoinsbelievedto be gold. Asample had a mass of129.6 g andhadavolumeof 15.3 cm3. Were the coins gold (d = 19.3g/cm3)or just yellow brass (d = 8.47g/cm3)? Show yourwork.129.6 g/15.3 cc = 8.47 g/ccToo bad, the metal is brass.8

Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition - Page 10 preview image

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namesectiondatepartnergrade2EXPERIMENT2Report SheetReport allmeasurementsandcalculationsto the correctnumberofsignificant figures.Density of a regular-shaped objectTrial 1Trial 2Unknowncodenumber1 (wood block)1.Length20.8cm20.8cmWidth5.3cm5.3cmHeight2. Volume (LWH)3.Mass4. Density:(3)/(2)Average densityofblock4.4cm485cm3287.57g0.593g/cm34.4cm485cm3287.62g0.593g/cm30.593g/cm3Density of an irregular-shaped objectTrial 1Trial 2Unknowncodenumber2 (Al shot)5. Mass of metalsample5.232g6.702g6. Initialvolumeofwater14.90mL16.80mL7. Finalvolumeofwater8. Volume of metal: (7)(6)9. Density of metal:(5)/(8)16.80mL1.90mL2.75g/mL19.30mL2.50mL2.68g/mLAverage densityofmetal2.72g/mL10.IdentityofunknownmetalAluminum9

Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition - Page 11 preview image

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DensityofwaterTrial1Trial211.Temperatureofwater22.08C22.08C12. Mass of 50-mLbeaker26.264g26.257gVolume of water10.00 mL10.00mL13. Mass of beaker andwater14. Mass of water: (13)(12)15. Density of water: (14)/10.00mL36.143g9.879g0.9879g/mL36.176g9.919g0.9919g/mL16.Average densityofwater0.998g/mLDensityfoundinliterature0.998g/mLDensity of an unknown liquidTrial 1Trial 2Unknowncodenumber3 (ethyl alcohol)17.Temperatureofunknown liquid22.08C22.08C18. Mass of 50-mLbeaker26.810g26.960gVolume ofliquid10.00 mL10.00mL19. Mass of beaker andliquid20. Mass of liquid: (19)(18)21. Density of liquid: (20)/10.00mL34.671g7.861g0.7861g/mL34.842g7.882g0.7882g/mLAverage densityofunknown liquid0.7872g/mL22.IdentityofunknownliquidEthyl alcohol10

Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition - Page 12 preview image

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Post-LabQuestions1.Indeterminingthedensityof olive oil (see Table 2.2), onestudenttook exactly 25.00 mLandfoundthe mass to be 22.95 g. A secondstudenttook exactly 50.00 mL andfoundthe mass tobe45.90 g. Will eachstudentarriveat the same value for thedensity?Do eachcalculationandexplaintheresult.22.95 g/25.00 mL = 0.918 g/mL45.90 g/50.00 mL = 0.918 g.mLEach student will arrive at the same value for the density because density is an intrinsicproperty; the ratio of mass to volume is the same.2 .Hexanehas adensityof 0.659g/mL.Howmanymilliliters(mL)wouldastudentneedto pourinorderto get 49.5 g of hexane?Show yourwork.If density = mass/volume then volume = mass/density or mL = g/g/mL = g x mL/g49.5 g/0.659 g/mL = 75.1 mL3. In thedensity determinationof aliquid,it wasnecessaryto use thevolumetricpipetproperly.Astudent neededtodeliverexactly 50.0 mL of aliquid.How will thequantityofliquidbeaffectedby thesituations describedbelow, and how will thedensity determinationbeaffected?a.A dirty pipetis usedanddropletsofliquid adheredto the inner walls of thepipet.Density determined decreases. The measured mass of the liquid delivered would be less than it should be(droplets remain in the piper), but the volume is still assumed to be 50.0 mL.b.Thestudentdid not allowsufficienttime for all theliquidtoemptyfrom thepipet.Density determined decreases. The mass measured would be less (not everything has beentransferred) but the volume is still assumed to be 50.0 mL.c.Thestudent allowedall theliquidtodrainand then blew out the smallamountfrom thetip.Density determined increases. The mass measured would be greater since more liquid has beendelivered than allowed for by calibration, but the volume is still assumed to be 50.0 mL.d.Airbubbleswere notremovedfrom the pipet beforedeliveringtheliquid.Density determined decreases. The mass measure would be less (air took up space of the liquid),but the volume is still assumed to be 50.0 mLe.At the markon the pipet,thestudentreadtheupperedge of themeniscusandnot thelowestpoint on thecurve.Density determined decreases. The mass measured would be less since less than 50.0 mL wouldbe delivered, but the volume is still assumed to be 50.0 mL.11

Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition - Page 13 preview image

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Experiment 3In this experiment students get to use a Bunsen burner to heat various mixtures. Remindstudents by means of a demonstration the workings of a Bunsen burner. The instructor shouldcheck to make sure that the ring clamp is secured tightly to the ring stand and set at the properheight above the flame. All heating should be done with a wire gauze under the beaker.A major source of error occurs in the gravity filtration of the stand. Remind the studentsto be careful and patient in the transfer. With the rubber policeman as an aid, all the sand can betransferred from the filter paper to the second beaker. Again care and patience will result in all ofthe sand being transferred.The evaporation of water needs to be carefully done. As the salt-water solution reachesdryness, the residual salt will spatter; the student must be prepared to pull away the Bunsenburner to reduce the heat when this occurs in order to minimize losses from solid flying out ofthe beaker. This also applies to drying of the sand; as the water evaporates from the sand, trappedvapor will cause spattering.Both the salt and the sand must be water free in order for the calculations to bemeaningful. The dry salt will appear as a cake; the dry sand should be freely flowing whenpoured.Provide a waste container to collect the used naphthalene. Sand and dried salt can bedisposed in solid waste containers.

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namesectiondatepartnergrade3EXPERIMENT3Pre-LabQuestions1.I make my cup of coffee in themorningbypouringboiling wateroverground-upcoffeebeansheldin a special piece ofpaperand by collectingthebrown liquidthat comesthrough. Which techniquesof the fivedescribedin theBackgroundsection is used in thepreparationof thedrink?Extraction is used.2. I like my coffee sweet, so I add atablespoonofsugarto my cup of coffee and the soliddisappears.What makes up the‘‘cupofcoffee’’now? Is this amixture?It is a mixture of dissolved sugar and extracted substances from the coffee bean.3.What is takingplaceduringthe processofsublimation?How is this processdifferent fromevaporation?Sublimination is a process that involves heating a solid until its molecules pass directly from thesolid phase into the gaseous phase. Evaporation involves molecules in the liquid phase escapinginto the gaseous phase.4 .Are any of thetechniques describedin theBackgroundsection a chemicalstate change?Explainyouranswer.No chemical state changes are involved, only physical state changes. This is because no chemicalbonds have been broken.13

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namesectiondatepartnergrade3EXPERIMENT3Report Sheet1. Mass of beaker 167.565g2. Mass of beaker 1 andmixture68.730g3. Mass ofmixture:(2)(1)1.165g4. Mass ofnaphthalenecollected0.095g5. a. Mass of beaker 1 and solid aftersublimation68.616gb. Mass ofnaphthalenebydifference:(2)(5a)0.114g6. Mass of beaker 267.959g7. Mass of beaker 2 and NaCl68.530g8. Mass of NaCl: (7)(6)0.571g9. Mass of beaker 355.765g10. Mass of beaker 3 and sand56.231g11. Mass of sand: (10)(9)0.466gCalculations12. Mass ofrecovered solids:(5b) + (8) + (11)1.151g13.Percentageyield(percentageof solidsrecovered):% ¼[(12)/(3)]10098.80%14.Percentageofnaphthalene:% ¼[(5b)/(3)]1009.79%15.PercentageofNaCl:% ¼ [(8)/(3)]10049.01%16.Percentageofsand:% ¼[(11)/(3)]10040.00%14

Solution Manual For Laboratory Experiments for Introduction to General, Organic and Biochemistry, 8th Edition - Page 16 preview image

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Post-LabQuestions1.Astudent completedtheexperimentbutfoundthat the totalamountofmaterial recoveredweighedmore than theoriginal sample.What is the most likely source of errorandhow may it becorrected?Most likely water is present. Heat to evaporate the water2. Astudent foundthat themassof thenaphthalenecollectedwas less than themassdeterminedbydifference.Whatwould accountfor the smalleramount ofnaphthalene collected?If naphthalene vapors escaped, then not all of the naphthalene was collected.3.Mothballsin a clothes closetgradually disappearover time. Whathappensto thismaterial?The solid mothballs sublimed.4.Apackageof freshly pickedsweet peashas a mass of454 g (1 lb.). The peas werefreezedriedand therecoveredpeasweighed122 g. What was lost? What is thepercentcompositionof this volatilecomponent?(454–122) /454 x 100 = 73.1 %5. In 100 g of sweet peas, there are 14.5 gcarbohydrates,5.7 gsugars,5.1 gdietary fiber,5.4 gprotein,and 0.4 g fat.Calculatethepercent compositionfor each of thesecomponents.14.5/100 x 100 = 14.5% carbohydrates5.1/100 x 100= 5.1% dietary fiber5.7/100 x 100 = 5.7% sugars5.4/100 x 100= 5.4% protein0.4/100 x 100 = 0.4% fat15

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