* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download CHM112 Lab – Heat of Neutralization – Grading Rubric
Thermodynamics wikipedia , lookup
Ultraviolet–visible spectroscopy wikipedia , lookup
Physical organic chemistry wikipedia , lookup
Rate equation wikipedia , lookup
Acid–base reaction wikipedia , lookup
Heat transfer physics wikipedia , lookup
Equilibrium chemistry wikipedia , lookup
Reaction progress kinetic analysis wikipedia , lookup
Countercurrent exchange wikipedia , lookup
George S. Hammond wikipedia , lookup
Enzyme catalysis wikipedia , lookup
Chemical equilibrium wikipedia , lookup
Heat transfer wikipedia , lookup
Thermal conduction wikipedia , lookup
Transition state theory wikipedia , lookup
Chemical thermodynamics wikipedia , lookup
Heat equation wikipedia , lookup
Name_________________________ TeamName______________________ CHM112Lab–HeatofNeutralization–GradingRubric Criteria Pointspossible Pointsearned LabPerformance Printedlabhandoutandrubricwasbroughttolab Safetyandproperwastedisposalproceduresobserved Followedprocedurecorrectlywithoutdependingtoomuch oninstructororlabpartner Workspaceandglasswarewascleanedup 3 2 3 1 11 20 LabReport CalculationsQ1-Q11(1pointeach) Total Subjecttoadditionalpenaltiesatthediscretionoftheinstructor. EnthalpyofNeutralization Introduction Inthecourseofmostphysicalprocessesandchemicalreactionsthereisachangeinenergy.Inchemistrywhat isnormallymeasuredisΔH(enthalpychange),thechangeinheatatconstantpressureandignoringanyworkdoneby thereactingsystem.Ifthereactionisexothermic,heatisgivenoffandΔHhasanegativevalue.Whenheatisabsorbed fromthesurroundingsduringthereaction,thereactionisendothermicandΔHhasapositivevalue.Thechangein enthalpyisameasureofthedifferenceinenergybetweenthebondsintheproductsandthebondsinthereactants. Theabsoluteenergyofacompoundcannotbemeasureddirectly,butthechangeinenthalpythatoccursduringa chemicalreactioncanbemeasured. Thereactionintoday’sexperimentisacid/baseneutralizationwhichisanexothermicprocess. HCl(aq)+NaOH(aq)→ H2O(l)+NaCl(aq)+heat Theheatreleasedbythereactionwillbeabsorbedbythesurroundings(aqueoussolution).CoffeeCup Calorimetrywillbeemployedtodeterminetheamountofheatlostbythereactionandgainedbythesaltwater solution.Acalorimeterissimplyacontainerusedtomeasuretheheatchange.CoffeeCupCalorimetryjustmeansthat wewillbemeasuringheatatconstantpressure,ΔH.Theheatlostbythereactionwillactuallybetransferredtoboth thesaltwateranditssurroundings(thecalorimeter.)Theheatcapacityofthecalorimeter(inthiscase,twoStyrofoam cups)usuallywouldbecalculatedfirst;however,wehavefoundthattheheatcapacityofthecupsissosmallthatitcan beneglected. AstheFirstLawofThermodynamicsapplies, Heat(q)lostbythereaction+heat(q)gainedbythesolution=0 orqrxn=–qsoln Tofindtheheatlostbythereactionweuse: q=mxCsxΔT where: m=massofthesolution(Thedensityofthesolutionis1.04g/mL) Cs=specificheatcapacityofthesolution(3.87J/g°C) ΔT=changeintemperatureofthesolution(Tfinal–Tinitial) Equipment 2Styrofoamcups (2)Thermometers 50or100mLgraduatedcylinder Stirringrod 150mLbeaker Chemicals 2.00MHCl 2.00MNaOH Procedure 1. RinseanddrytheStyrofoamcups(calorimeter).Placeonecupinsidetheother.Measureout25.0mLof2.00M NaOHandpouritintothecalorimeter.Inacleandry150mLbeaker,take25.0mLof2.00MHCl. 2. Determinethetemperatureofboththeacidandthebasetothenearest0.1°C.Averagethetemperatures.Record thisaverageastheinitialtemperatureTinitial. 3. Pourtheacidintothebasequicklyandcarefullywithgentlestirring.Startmonitoringthetemperatureassoonas thetwoaremixed.Continuetostirandmonitorthetemperature.Recordthemaximumtemperaturethatthe solutionreaches.ThisisTfinal 4. RepeatSteps1-3(above)forasecondtrial. Disposal Allreactantsandproductsmaybedisposedofintothesink. HeatofNeutralization:DataSheet Name________________________ Trial1 Trial2 Volumeof2.00MHCl Volumeof2.00MNaOH Volumeofsolution Tinitial Tfinal ΔT(Tfinal—Tinitial) SpecificheatcapacityofNaClsolution 3.87J/g°C 3.87J/g°C Calculations(Showallyourworkcompletelyandclearly.Includeproperunits) 1. Calculatethemassofthesolutionforeachtrial(giventhedensityofthesolutionis1.04g/ml) 2. Calculatetheheatabsorbedbythesolutionineachtrial.(qsoln) qsoln(Trial1)____________ qsoln(Trial2)_____________ Averageqsoln_________ 3.Calculateqrxn=____________________________ 4.Calculatethenumberofmolesofwaterformed(ThisisthesameasmolesofHCl): molesofwater=molesofHCl=__________________ 5.CalculateΔHneutralization(ΔH°)permoleofwater(kJ/mole)formed.Makesurethesigniscorrect. ΔH°=_________________ ReportPage1of2 HeatofNeutralization:Calculations Name________________________ 6.Writethechemicalreactionfortheautoionizationofwater(equilibriumconstantKw). 7.LookupthenumericalvalueforKwatTinitial(TaketheaverageofTinitialfrombothtrials) 8.Howisthereactioninquestion1relatedtothenetionicreactionfortheneutralizationshownbelow? H3O+(aq)+OH—(aq)DH2O(l)+H2O(l) 9.UsethevalueofKwandtherelationshipbetweenthereactionsinquestions1and3tofindthenumericalvaluefor theKfortheneutralizationreactioninquestion3. 10.GiventheKcalculatedfortheneutralizationreaction,calculateΔGofortheneutralizationreaction.(Useaverage initialTfromthetwotrialsforthereactionTemperature.) 11.FromΔGoabove,andtheΔH°thatyouhavecalculated,calculatetheΔS°forthereaction.(UseaverageinitialT fromthetwotrialsforthereactionTemperature.) ReportPage2of2