Ma PChem 10/12, 10/14, 10/16
Ma PChem 10/12, 10/14, 10/16 CHEM 345
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This 3 page Class Notes was uploaded by Kayli Antos on Friday October 16, 2015. The Class Notes belongs to CHEM 345 at Towson University taught by Dr. Ma in Summer 2015. Since its upload, it has received 25 views. For similar materials see Physical Chemistry in Chemistry at Towson University.
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Date Created: 10/16/15
P Chem Ma Fall 2015 4L Gibbs And Helmholtz Energies And Their Application 6 At constant temperature ASWT M oz At constant pressure qsys qp 2 AH so ASSWT O 90 T T AH T Gibbs Energy G J G H TS Is a state function Is an extensive property SI unit is Joules At constant temperature AG AH TAS If AG lt O the reaction is exergonic work producing and spontaneous If AG O the reaction is reversible and at equilibrium If AG gt O the reaction is endergonic work consuming and not spontaneous Helmholtz Energy A U J Used for constant temperature and volume A U TS If AA lt O the reaction is spontaneous If AA O the system is at equilibrium If AA gt O the reaction is non spontaneous SI unit is Joules Is a state function Is an extensive property tandard Molar Gibbs Energy Of Formation Af o The change in Gibbs energy during the formation of one mole of any compound at one bar from its elements in their standard state For a general reaction of aA b8 9 cC dD AGquot 2 Z uAfCO products Z TIA 50 reactants AG AH TAS The Meaning Of Gibbs Energy J J G H TS For an infinitesimal change dG dH dTS dG dU PV TdS SdT dG dU PdV VdP TdS SdT dG dq dwPdVVdP TdS SdT J ds for a reversible path drev TdS J dwrev devreV dwnonpvrev expansion nonexpansion dWPVrev 39PdV CIG CICIrev CIWrev PdV VdP TCIS SdT CIG CIWnoanrev VdP SdT J At constant temperature and pressure AG WnonPVrev J For a process with only expansion work d6 VdP SdT Dependence of Gibbs Energy On Temperature At constant pressure d6 SdT For molar quantities d6 dT jg d6 fde 62 a 725am Assume molar entropy is constant between T1 and T2 A6 AT 5o gt 5w gt go Where the molar Gibbs energy of two states is equal AGO and the reaction is at equilibrium and reversible J When AGlt0 GlltGZ Dependence Of Gibbs Energy On Pressure J At constant temperature d6 VdP d6 VdP J Integrate both sides AG f122l7dP J For condensed states solid and liquid A6 VAP J For gases assume ideal gas behavior A6 f zlgdP A5 RTflffgdp A5 RTln quot Va gt 17s AG 2 nRT 1n like the equation for work at constant temperature CI G CIWnonPVrev Integrate both sides w nRT 1nE V1 The Clapeyron And The ClausiusCapeyron Equation J For a substance that exists in phases a and B J At constant pressure and temperature a B and 6 63 J For an infinitesimal change d6 dGB VadP fadT VBdP SBdT VadP VBdP fadT SBdT Al7dP A dT d P A f dT AV A17 dP A17 J Since A mq P T T T dT TAV The T is the transition temperature which is the Clapeyron Equation J For the change between a condensed phase and gas the change in volume is about equal to the volume of the gas since the volume of the condensed phase is negligible 3 7 E J Can assume ideal gas behavior to get 2 21 which is the differential form of the ClausiusClapeyron Equation J Separate variables d P A HZdT P RT J Integrate both sides fpplzgdP fgz dT Assuming change in molar enthalpy is constant 1namp A H 1 i i which is the P1 R T2 T1 integrated form of the ClausiusClapeyron Equation It s used for phase transitions involving gas assume ideal gas behavior assume change in molar enthalpy is constant at constant temperature and pressure two sets of equilibrium 3 Normal BP indicates a pressure of 1 atm