problem_set_03

problem_set_03 - 1. 2. 3. 4. 5. 6. 7. 8. Chem110A,F09...

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Unformatted text preview: 1. 2. 3. 4. 5. 6. 7. 8. Chem110A,F09 ProblemSet3 InEq.(4.20)[Eq.(4.24)in1stedition]andintheequationatthetopofpage2in LECTURE#9thesumisoverallreactantsandproducts,whereasinEq.(4.8)[Eq. (4.12),1stedition]thesumisoveronlythosereactantsandproductsthatarenot elementsintheirstandardstates(i.e.,thestableformsoftheelementsatstandard temperature[298K]andpressure[1atm]). WHY? ConvinceyourselfthatEqs.(4.1920)[Eqs.(4.2324)in1stedition]followfromEq. (4.18)[Eq.(4.22)]. ThemolarconstantpressureheatcapacitiesforO2(g),H20(g),andCO2(g)are3.53R, 4.04R,and4.46R,respectively. EXPLAIN. HINT:Considerthenumbersofrotationaldegreesoffreedominvolved,andthe extentstowhichthevibrationsofthemoleculesareabletotakeup(store)energy. Thecombustionofa4.76gmassofsolid,elemental,potassiumiscarriedoutina constantvolume("bomb")calorimeterliketheoneconsideredinthebook;theinner waterbathconsistsof1.45kgofwater,andthevalueofthe"calorimeterconstant", i.e.,itsheatcapacity,is1.85kJ/K.Uponconversionofthe4.76gofpotassiumtoK20 (g),thetemperatureoftheinnerwaterbathisobservedtoincreaseby5.82K. CalculatethestandardenergiesandenthalpiesofformationofK20. Writetheexpressionthatallowsyoutocalculatethestandardenthalpychangeatan arbitrarytemperatureTforthereactionH2(g)+1/2O2(g)H2O(g). Estimatethevalueofthestandardenthalpyofformationofgaseousatomicoxygen [O(g)]fromthebonddissociationofgaseousdiatomicoxygen[O2(g)]. Calculatethestandardenthalpyandenergyofreaction,at298K,forthereaction 4NH3(g)+6NO(g)5N2(g)+6H20(g). Calculatethestandardenthalpyofreaction,at720K,forthesamereactionasinthe precedingproblem.Firstusetemperaturedependentheatcapacities,andthen comparetheresultyougetwithwhatyou'dfindusingconstantheatcapacities. ...
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