6b hot pack calorimetry - health and science pipeline ... · hot pack calorimetry teacher...

HASPIMedicalChemistryUnit6:Energy Lab6b, Page1

HASPIMedicalChemistryLab6bHotPackCalorimetryTeacherInformationLabOverviewInthislabstudentsmeasuretheamountofenergyreleasedinthetypeofreactionthatoccursinahotpack.BylinkingthistothehydratedcrystalslabinthefallwherestudentsheatedEpsomsalts(magnesiumsulfatehydrate)untiltheylostallwater,studentsareabletoquantifytheenergythattheystoredintheiranhydratepelletsincethelastlaboccurred.ToquantifythistheymustdissolvetheanhydrateinwateraswellasthehydrateanduseHess’lawtofindthedifference.Theanhydratedissolvinginwaterisanexothermicreaction.Thehydrate(Epsomsalts)dissolvinginwaterisaslightlyendothermicreaction.Studentswillexperiencebothtypesofreactionsinthislab,andtheywillturnpotentialenergytheyputintotheiranhydrateinthepreviouslabbackintokineticenergywhichtheycanmeasureastheincreaseinwatertemperature.NextGenerationScienceStandards

NGSS/CommonCoreStateStandardsStudentswhodemonstrateunderstandingcan:HS‐PS1‐4:Developamodeltoillustratethatthereleaseorabsorptionofenergyfromachemicalreactionsystemdependsuponthechangesintotalbondenergy.HS‐PS3‐1:Createacomputationalmodeltocalculatethechangeintheenergyofonecomponentinasystemwhenthechangeinenergyoftheothercomponent(s)andenergyflowsinandoutofthesystemareknown.HS‐PS3‐3:Design,buildandrefineadevicethatworkswithingivenconstraintstoconvertoneformofenergyintoanotherformofenergy.HS‐PS3‐4:Planandconductaninvestigationtoprovideevidencethatthetransferofthermalenergy,whentwocomponentsofdifferenttemperaturesarecombinedwithinaclosedsystem,resultsinamoreuniformenergydistributionamongthecomponentsinthesystem(secondlawofthermodynamics).MedicalApplication:Hotpacksandcoldpacksarechemicalreactionsthatstudentswillstudy.

ScienceandEngineeringPracticesDevelopingandUsingModelsDevelopamodelbasedonevidencetoillustratetherelationshipsbetweensystemsorbetweencomponentsofasystem.UsingMathematicsandComputationalThinkingCreateacomputationalmodelorsimulationofaphenomenon,designeddevice,process,orsystem.ConstructingExplanationsandDesigningSolutionsDesign,evaluate,and/orrefineasolutiontoacomplexreal‐worldproblem,basedonscientificknowledge,student‐generatedsourcesofevidence,prioritizedcriteria,andtradeoffconsiderations.PlanningandCarryingOutInvestigationsPlanandconductaninvestigationindividuallyandcollaborativelytoproducedatatoserveasthebasisforevidence,andinthedesign:decideontypes,howmuch,andaccuracyofdataneededtoproducereliablemeasurementsandconsiderlimitationsontheprecisionofthedata(e.g.,numberoftrials,cost,risk,time),andrefinethedesignaccordingly.

DisciplinaryCoreIdeasPS1.A:StructureandPropertiesofMatterAstablemoleculehaslessenergythanthesamesetofatomsseparated;onemustprovideatleastthisenergyinordertotakethemoleculeapart.PS1.B:ChemicalReactionsChemicalprocesses,theirrates,andwhetherornotenergyisstoredorreleasedcanbeunderstoodintermsofthecollisionsofmoleculesandtherearrangementsofatomsintonewmolecules,withconsequentchangesinthesumofallbondenergiesinthesetofmoleculesthatarematchedbychangesinkineticenergy.

DisciplinaryCoreIdeas(continued)

HASPIMedicalChemistryUnit6:Energy Lab6b,Page2

PS3.A:DefinitionsofEnergyEnergyisaquantitativepropertyofasystemthatdependsonthemotionandinteractionsofmatterandradiationwithinthatsystem.Thatthereisasinglequantitycalledenergyisduetothefactthatasystem’stotalenergyisconserved,evenas,withinthesystem,energyiscontinuallytransferredfromoneobjecttoanotherandbetweenitsvariouspossibleforms.Atthemacroscopicscale,energymanifestsitselfinmultipleways,suchasinmotion,sound,light,andthermalenergy.PS3.B:ConservationofEnergyandEnergyTransferConservationofenergymeansthatthetotalchangeofenergyinanysystemisalwaysequaltothetotalenergytransferredintooroutofthesystem.Energycannotbecreatedordestroyed,butitcanbetransportedfromoneplacetoanotherandtransferredbetweensystems.Uncontrolledsystemsalwaysevolvetowardmorestablestates—thatis,towardmoreuniformenergydistribution(e.g.,waterflowsdownhill,objectshotterthantheirsurroundingenvironmentcooldown).Mathematicalexpressions,whichquantifyhowthestoredenergyinasystemdependsonitsconfiguration(e.g.relativepositionsofchargedparticles,compressionofaspring)andhowkineticenergydependsonmassandspeed,allowtheconceptofconservationofenergytobeusedtopredictanddescribesystembehavior.Theavailabilityofenergylimitswhatcanoccurinanysystem.PS3.D:EnergyinChemicalProcessesAlthoughenergycannotbedestroyed,itcanbeconvertedtolessusefulforms—forexample,tothermalenergyinthesurroundingenvironment.ETS1.A:DefiningandDelimitinganEngineeringProblemCriteriaandconstraintsalsoincludesatisfyinganyrequirementssetbysociety,suchastakingissuesofriskmitigationintoaccount,andtheyshouldbequantifiedtotheextentpossibleandstatedinsuchawaythatonecantellifagivendesignmeetsthem(secondary).

CrosscuttingConceptsEnergyandMatterChangesofenergyandmatterinasystemcanbedescribedintermsofenergyandmatterflowsinto,outof,andwithinthatsystem.SystemsandSystemModelsModelscanbeusedtopredictthebehaviorofasystem,butthesepredictionshavelimitedprecisionandreliabilityduetotheassumptionsandapproximationsinherentinmodels.ConnectionstootherDCIsinthisgrade‐band:HS.PS1.A;HS.PS1.B;HS.PS2.B;HS.LS2.B;HS.ESS1.A;HS.ESS2.A;HS.ESS2.D;HS.ESS3.A;HS.PS3.A;HS.PS3.B;HS.PS3.D;HS.LS1.CArticulationofDCIsacrossgrade‐bands:MS.PS1.A;MS.PS2.B;MS.PS3.A;MS.PS3.B;MS.PS3.C;MS.ESS2.A;MS.PS3.D;MS.LS1.CCommonCoreStateStandardsConnections:ELA/Literacy

RST.11‐12.1 Citespecifictextualevidencetosupportanalysisofscienceandtechnicaltexts,attendingtoimportantdistinctionstheauthormakesandtoanygapsorinconsistenciesintheaccount.(HS‐PS3‐4)

WHST.9‐12.7 Conductshortaswellasmoresustainedresearchprojectstoansweraquestion(includingaself‐generatedquestion)orsolveaproblem;narroworbroadentheinquirywhenappropriate;synthesizemultiplesourcesonthesubject,demonstratingunderstandingofthesubjectunderinvestigation.(HS‐PS3‐3),(HS‐PS3‐4),(HS‐PS3‐5)

WHST.11‐12.8 Gatherrelevantinformationfrommultipleauthoritativeprintanddigitalsources,usingadvancedsearches effectively;assessthestrengthsandlimitationsofeachsourceintermsofthespecifictask,purpose,andaudience;integrateinformationintothetextselectivelytomaintaintheflowofideas,avoidingplagiarismandoverrelianceonanyonesourceandfollowingastandardformatforcitation.(HS‐PS3‐4),(HS‐PS3‐5)

WHST.9‐12.9 Drawevidencefrominformationaltextstosupportanalysis,reflection,andresearch.(HS‐PS3‐4),(HS‐PS3‐5)SL.11‐12.5 Makestrategicuseofdigitalmedia(e.g.,textual,graphical,audio,visual,andinteractiveelements)inpresentationsto

enhanceunderstandingoffindings,reasoning,andevidenceandtoaddinterest.(HS‐PS3‐1),(HS‐PS3‐2),(HS‐PS3‐5),(HS‐PS1‐4)

CommonCoreStateStandardsConnections:MathematicsMP.2 Reasonabstractlyandquantitatively. (HS‐PS3‐1), (HS‐PS3‐2), (HS‐PS3‐3), (HS‐PS3‐4),(HS‐PS3‐5)MP.4 Modelwithmathematics.(HS‐PS3‐1), (HS‐PS3‐2), (HS‐PS3‐3), (HS‐PS3‐4), (HS‐PS3‐5),(HS‐PS1‐4)HSN.Q.A.1 Useunitsasawaytounderstandproblemsandtoguidethesolutionofmulti‐stepproblems;chooseandinterpretunits

consistentlyinformulas;chooseandinterpretthescaleandtheoriginingraphsanddatadisplay.(HS‐PS3‐1),(HS‐PS3‐3),(HS‐PS1‐4)

HSN.Q.A.2 Defineappropriatequantitiesforthepurposeofdescriptivemodeling. (HS‐PS3‐1),(HS‐PS3‐3),(HS‐PS1‐4)HSN.Q.A.3 Choosealevelofaccuracyappropriatetolimitationsonmeasurementwhenreportingquantities.(HS‐PS3‐1),

(HS‐PS3‐3),(HS‐PS1‐4)


ObjectivesBytheendofthislabstudentswillbeableto:

Calculatetheenergygainedorlostinachemicalreactionusingcalorimetry. UseHess’lawtorelatetwoexperimentalreactionsinordertodeterminethechangeinenergyfor

thesumofthosereactions.Time

EstimatedTime

ActualTime(pleasemakenotebelow)

Pre‐Lab:20‐30Minutes

Lab:40minutesorless

PostLabCalculations:1hour

Materials

Suppliesneededfor5sections

Provided(P)or

Needed(N)

Quantity

Company/Item#

ApproximateCost

EpsomSalts P 2‐3gpergroup

Grocery/DrugStore

$3

AnhydrousmagnesiumsulfateYoushouldhavesavedthisfromlab4a*seelabnotesforanotheroption

P(ifyoudid4a)

2‐3gpergroup

FlinnM0115

$17

Studentmadecalorimetersfromlab6a 1pergroup Thermometers 1pergroup Balance GraduatedCylinderstomeasure20mLofwater

Accesstowater PrerequisiteKnowledgeStudentsshouldalreadyknowthefollowinginformation:

Theuseoftheequationq=cmΔT Thetermsendothermicandexothermic ConversionbetweenkelvinandCelsius

LabSetup Studentscanusetheirowncalorimetersfromlab6a.Ifnot,youcanmakeyourownfoamcup

calorimeter.Tomake10calorimetersbuy10largecupsand20smallcups.Placeasmallcupinsideeachlargecuptocreateaninsulateddevice.Pokeathermometersizedholeintheothersmallcupanduseitforalid.

Eachgroupneedsathermometerandwillneedtoweighouttwoseparatesubstances.Provideasmanybalancesasyouthinkyouwillneed.

CompanyContactInformationFlinnScientific

http://www.flinnsci.com/


LabNotes&CommonMisconceptions TheBackgroundandReviewquestionsareaperfectpre‐labassignmenttosendhomewith

studentsashomeworkbeforethelab. Ifyoudidlab4ayoushouldhavekeptthesmalldriedpellets.Itisbestiftheyarekeptinasealed

ziptopbag,butIhavestillhadsuccesswhentheyareleftout. Ifyoudidnotdolab4ayouhaveafewoptions.

o YoucanpurchasetheanhydratefromachemicalcompanysuchasFlinn.o YoucananhydratetheEpsomsaltathome.Itneedstoreachatleast450degreesto

anhydratesoyoucanputitinyourovenforawhileatahightemperature.Itshouldbeapproximatelyhalftheweightattheendasitis51.2%water.

o IfyouhaveBunsenburnersandcruciblesthestudentscancreatethemagnesiumsulfateanhydratefromEpsomsaltsbyfollowingtheprocedurelistedinlab4a.Thepelletmustbecooledbeforeitcanbeusedforthislab.Itwilltakeabout10minutestoanhydratebyBunsenburnerandanother10minutestocool.

Thesecondreactionismildlyendothermic,sostudentswillseeonlya1‐2degreechangeintemperature.TheyareoftensurprisedtoseeanendothermicreactionsoIfinditbestnottotellthemaheadoftimesotheydiscoveritthemselves.

Thefirstreactionshouldhave3significantfiguresincalculationsandthesecondreactionshouldonlyhavetwosignificantfiguresincalculationsdependingonthetemperaturechangetheysaw.It’sbestthatyoureviewsignificantfiguresrulesbeforethelabtoensuretheydotheircalculationsproperly.

Letusknowhowitwent!Gotowww.HASPI.org/feedbacktoshareyoursuggestions&successes.Connections&ApplicationLab4aandlab6ahavestrongconnectionstothislab.Ifyouhavealreadydonetheselabsyoumightreviewthemwithyourstudentsbeforedoingthislabtohelpthemmakeconnections.

Askstudentstostudythereactionsthathavetodowithcoldpacks. MRE’sor“MealsReadytoEat”areamilitarystaplethatself‐heat.Havestudentsstudythe

reactionandfindouthowmuchenergyisneededforthese. Havestudentscreateabrochureeducatingapatientonwhentouseheattherapyandcoldtherapy. Drawanenergydiagramforeachofthethreereactionsshowingthechangeinenergy. Createavideoanimationoftheprocessesobservedinthislab. Explorethethermodynamicsofotherheatpackreactioningredientssuchasironpowder.

References:http://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=1&ContentID=4483http://www.spine‐health.com/treatment/heat‐therapy‐cold‐therapy/benefits‐heat‐therapy‐lower‐back‐painhttp://www.middleschoolchemistry.com/lessonplans/chapter5/lesson9http://home.howstuffworks.com/question290.htmhttp://prezi.com/lranljsxv4hx/copy‐of‐chemistry‐hotcold‐packs/http://www.chemistryland.com/CHM130FieldLab/Lab11/Lab11.html


HotPackCalorimetryHASPIMedicalChemistryLab6bBackground/Introduction

Manycommonreactionsinchemistrycausetemperaturechanges.Endothermicreactionsabsorbheat,makingtheenvironmentaroundthemfeelcolder.Exothermicreactionsreleaseheat,makingtheenvironmentaroundthemfeelwarmer.Wecanusethesereactionstoprovidethermotherapysothattreatmentcanbequickandcanbeavailableanywhere.Thermotherapyistheuseofheatorcoldtotreataninjuryorillness.Weusechemicalreactionstocreateheatpacksandcoldpacks.

Coldpacksareusedmostoftentoreduceinflammationandswelling.Thisisbestforanewinjury.

Coldtherapydecreasesbloodflow Lessbloodflowleadstolessswellingandinflamation Coldtherapyisidealforanareathatisswollenorbruised Coldtreatmentisbestduringthefirst24‐48hoursafteraninjury Coldtherapyshouldoccurfor20minutesatatimewithatleast10minutesbetweenapplications

Hotpacksareusedtoprovidepainrelief.,Commonusesareforbackpainorarthritispain.Thistreatmentisbestforrecurringpain.

Bloodvesselsaredilatedsothatthereisanincreasedflowofbloodtothemuscles Bloodflowbringsoxygenandnutrientssothatdamagedtissuecanheal Theheatallowssofttissuestostretchsothatthereisdecreasedstiffnessandincreasedflexibility

Thiscangreatlyincreasetherangeofmotion Heatcanrelaxjoints,muscles,ligamentsandtendons Heattherapyshouldoccurin20minuteincrements

HotPackChemistryThereareafewwaysthatexothermicreactionscanbeusedashotpacks.Thereactionwewillstudytodaymixesanhydrousmagnesiumsulfate(MgSO4)withwater.Whenthesemixheatisreleased.InahotpackthereispowderedMgSO4alongwithasmallbagofwater.Whenyousqueezethehotpack,thewaterpacketburststobeginthereaction.Thistypeofhotpackcanonlybeusedonetime.Anothertypeofhotpackusesasupersaturatedsolutionofsodiumacetate.Sodiumacetatehasaboilingpointof130°F,butifyoumeltitbyheatingitabovethattemperature,youcancoolitbackdownanditwillstayaliquiduntilsomethingcausesjustonemoleculetofreeze.Thiscausesachainreactionuntilallofthesodiumacetatefreezes.Inorderforthemoleculestosolidifyandfreeze,theenergywithinthemmustbereleased,whichiswhythisfeelshotinyourhands.Thesehotpacksarereusableaslongasyouboilthemtodissolveormeltthesodiumacetateagain.

http://www.chemistryland.com/CHM130FieldLab/Lab11/Lab11.html

Name(s): Period: Date:


Ironfilingscanalsobeusedasahotpack.Theyreactwithoxygenintheair,sotheyareinameshpacketwhichissealedinsideofthepackaging.Onceopened,theironfilingsreactwiththeoxygeninthesamewaytheyreacttocreaterust,butithappensveryquicklybecausetheironisinverysmallpieces.Waterisabletospeedupthisreaction,increasingtheheatforamoment,buttheheatpackwillcoolmorequicklyifthereactionspeedsup.ColdPackChemistryEndothermicreactionscanbeusedascoldpacks.Acommonlyusedcoldpackcontainsammoniumnitrateandwater.Whenthesmallbagofwaterinsideisputunderpressureitburststobegintheendothermicreaction.Thisreactionneedsenergy,soittakestheenergyfromyou,makingyoufeelcold.Coldisjustthesensationofenergymovingawayfromyou.ANewConcept‐Calorimetry!Todaywewillusecalorimetrytostudytheenergygivenoffbyourreactions.Calorimetryallowsustomeasuretheenergygiventowaterbyareaction,orbyahotmetal.Thisisusedtofindtheamountofenergyinourfood,toidentifyunknownmetals,andinthiscase,tofindtheEnthalpyofHydrationforoursubstance.Incalorimetrywearegoingtodoareactioninaverywellinsulatedcontainer,whichwewillmakefromstyrofoamcups.Asthereactionproceeds,thewaterwillabsorbtheenergyreleased.Wecanuseathermometertomeasurethechangeintemperatureofthewater,thenusethereactionq=mcΔTinordertofindoutthequantityofenergythatwasreleased!

ReviewQuestions1. Whatisthedifferencebetweenanexothermicandendothermicreaction?2. Howdoyouchoosewhichtherapyisrightforyourinjury?3. Whywouldn'tahotpackhelpwithswelling?4. Howdoyouthinkyoumightbeabletore‐usethechemicalsinaMagnesiumSulfatehotpack?5. Ifthereactioncreatingrust(IronOxide)isexothermic,whydon'trustycarsandnailsfeel

warm?6. Whatdoesthecoldsensationmeaninchemistry?7. Whydoweneedaninsulatedcontainerforcalorimetry?8. Whaterrorsdoyoupredictwewillencounterinacalorimetrylab?

Reaction

Heat q=m c ΔT

energyinJoules

massingrams

specificheat

changeintemperature


HotPackCalorimetryHASPIMedicalChemistryLab6b ObjectivesFindtheamountofenergyreleasedwhenMgSO4isrehydratedtoformMgSO47H2OSpecifically:

CalculatetheEnthalpyofHydration(ΔH)forMgSO4 LearnCalorimetrytechniques ApplyHess'Law Usetheequationq=mcΔT

Materials

FoamCupCalorimeter Thermometer AnhydrousMgSO4 MgSO47H2Ocrystals

DIordistilledwater DigitalBalanceandweighboats 50mlor100mLGraduatedcylinder

ConnectionstopastlabYoupreparedtheanhydratebyheatingtheMgSO47H2O(s)lastsemesterinthehydratedcrystalslab.Ittookheattoremovethewaterfromthecrystals,whichmeantitwasanendothermicreaction.ThatenergyhasbeenstoredintheanhydrateandwhenthereactionisreversedtheenergyyouputintotheMgSO4withyourBunsenburnerwillnowbereleasedinanexothermicreaction. ScenarioInthislabwewilldissolveMagnesiumSulfatehydrate(MgSO47H2O)andmagnesiumsulfateanhydrate(MgSO4)tofindtheΔHvaluesforeachprocess.Ahydrateisachemicalwithwatertrappedinitscrystallinestructure.Whenyoulookatthehydrateyouwillnoticeitlooksdry,notwet.Thatisbecausethewateristrapped.Weuseadotintheformulaofahydratetoshowthatthewatermoleculesaretrapped.InordertofindtheΔH(enthalpyofhydration)wewillperformtwoseparateexperiments,andthenrelatethemtofindourgoalreaction.Reaction1:MgSO4(s)Mg+2(aq)+SO4‐2(aq)Herewewilladdwatertotheanhydratetodissolvethesubstance.Reaction2:MgSO47H2O(s)Mg+2(aq)+SO4‐2(aq)+7H2O(l)Herewewilldissolvethehydratedcrystalinwater.GoalReaction:MgSO4(s)+7H2O(l)MgSO47H2O(s)ByaddingtheabovereactionstogetherwecandeterminetheΔHforthisreaction.

H2O

H2O

Name(s): Period: Date:

H2O


UsingHess'lawyoucanreversethesecondreactionandaddittothefirstinordertocalculatetheΔHofthegoalreaction.FirstwewillcalculatetheΔHforreaction1andreaction2usingcalorimetry.ProcedureandcalculationsforReaction1:MgSO4(s)Mg+2(aq)+SO4‐2(aq)1.ObtainasampleoftheanhydrousMgSO4.WeighthesampleandrecordthemassinDataTable1.Itshouldbeabout1.50‐3.00g.2.Addexactly20.0mLofDIwatertoyourcalorimeter.3.Recordtheinitialtemperatureofthewater.4.AddtheMgSO4anhydratetoyourcalorimeterandimmediatelyclosethelid.5.Stiruntilthetemperaturestopsincreasing.6.Recordthehighesttemperaturereachedasthefinaltemperature.

DATATABLE1MassofanhydrousMgSO4pelletorpowder

Massofwaterused(sameasmL)

Initialtemperatureofthewater

FinalTemperatureofthewater

ΔT(Final‐Initial)

CalculationsforReaction11.Useq=mcΔTtofindouthowmanyjoulesofenergywereabsorbedbythewater.Rememberthatthespecificheatofwateris4.184J/g°C.Besuretousethemassofwaterforthiscalculation.(Forwater1mL=1g)

a)EnergyinJoulesb)EnergyinkJ

2.Findthemolesofanhydrateuseda.WhatisthemolarmassofMgSO4?b.ConvertthegramsofMgSO4inDataTable1intomoles

a)molarmassofMgSO4

b)molesofMgSO4used

3.FindthejoulesofheatreleasedfromthereactioninkJ.Remember,energyabsorbedbywaterisnegativetheenergyreleasedfromthereaction.

Energy=

4.FindtheΔHforthisreactioninkJ/mol.(dividekJbymoles)

ΔH1=

5.Isthisreactionendothermicorexothermic?

H2O


ProcedureandcalculationsforReaction2: MgSO47H2O(s)Mg+2(aq)+SO4‐2(aq)+H2O(l ) 1.Weighoutabout2.00gofcrystalline MgSO47H2O 2.Addexactly20.0mLofDIwatertoyourcalorimeter3.Recordtheinitialtemperatureofthewater4.AddtheMgSO4hydratedcrystalstoyourcalorimeterandimmediatelyclosethelid5.Stiruntilthetemperaturestopsincreasing6.Recordthefinaltemperaturereachedbythesolutionafteritstopschanging

DATATABLE2

MassofMgSO47H2O

Massofwaterused(sameasmL)

Initialtemperatureofthewater

FinalTemperatureofthewater

ΔT(Final‐Initial)

CalculationsforReaction21.Useq=mcΔTtofindouthowmanyjoulesofenergywereabsorbedbythewater.Rememberthatthespecificheatofwateris4.184J/g°C.Besuretousethemassofwaterforthiscalculation.(Forwater1mL=1g)

a)answerinJoulesb)answerinkJ

2. Find the moles of anhydrate used a. What is the molar mass of MgSO47H2O? b. Convert the grams of MgSO47H2O in Data Table 2 into moles

a) molar mass of MgSO7H2O4

b) moles of MgSO47H2O used

3. Find the joules of heat absorbed in the reaction in kJ. Remember, energy lost by water is negative the energy gained by the reaction.

Energy=

4. Find the ΔH for this reaction in kJ/mol. (divide kJ by moles)

ΔH2 =

5. Is this reaction endothermic or exothermic?

H2O


Conclusions: Calculate the ΔH for the goal reaction using the given reactions 1. Label each reaction with the enthalpy of reaction you found in the lab Reaction 1: MgSO4(s) Mg+2(aq) + SO4-2(aq) ΔH1 = Reaction 2: MgSO47H2O (s) Mg+2(aq) + SO4-2(aq) + 7H2O(l) ΔH2 =

2. In order to find the goal reaction, the above reactions may be reversed or multiplied as needed so that they add up to make this reaction: MgSO4(s) + 7H2O(l) MgSO47H2O (s) Remember that a reversed reaction causes the sign on the ΔH value to reverse, and a doubled reaction doubles the ΔH value. Cancel out anything that appears on both sides of the arrows. Show your work as you add these reactions together: Reaction 1: ΔH = + Reaction 2: ΔH = Equals Goal Reaction MgSO4(s) + 7H2O(l) MgSO47H2O (s) ΔH = 3. When you add together the ΔH values, what is the ΔH of hydration for MgSO4? 4. If the theoretical value is -104kJ/mol, what is the percent error? 5. List 2 sources of unavoidable error

H2O

H2O


Applications:

1.Explainthedifferencebetweenpotentialenergyandkineticenergyin2‐3sentences.

2.Usingthetermspotentialandkineticenergy,describewhathappenedinthefirstreaction,whereyoudissolvedtheanhydrateinwater.

3.Thelawofconservationofenergystatesthatthetotalenergyofanisolatedsystemcannotchange.Howdoesthisapplytoourlab?4.Whatcouldyoudotoincreasetheamountofenergyreleasedinreaction1?5.Attheendofthetrial,thetemperaturebegantodecrease.Whathappenedtotheenergythatwasinthecalorimeter?

6.Whatchangescouldyouhavemadetothelabapparatustoimproveyourresults,reducingyourpercenterror?


7.Drawadiagramofeachexperiment,includingthecalorimeter,thechemicalandthewater.Usearrowstoshowtheflowofenergybetweenthemagnesiumsulfateandthewater.Experiment1:DissolvingtheAnhydrate

Experiment2:DissolvingtheHydrate

ResourcesandReferenceshttp://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=1&ContentID=4483http://www.spine‐health.com/treatment/heat‐therapy‐cold‐therapy/benefits‐heat‐therapy‐lower‐back‐painhttp://www.middleschoolchemistry.com/lessonplans/chapter5/lesson9http://home.howstuffworks.com/question290.htmhttp://prezi.com/lranljsxv4hx/copy‐of‐chemistry‐hotcold‐packs/Pictures:http://www.chemistryland.com/CHM130FieldLab/Lab11/Lab11.html

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