Ma Physical Chemistry 10/5, 10/7, 10/9
Ma Physical Chemistry 10/5, 10/7, 10/9 CHEM 345
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This 2 page Class Notes was uploaded by Kayli Antos on Friday October 9, 2015. The Class Notes belongs to CHEM 345 at Towson University taught by Dr. Ma in Summer 2015. Since its upload, it has received 21 views. For similar materials see Physical Chemistry in Chemistry at Towson University.
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Date Created: 10/09/15
P Chem Ma Fall 2015 The Second Law Of Thermodynamics Disordered states are more probably than ordered states Entropy S gt The measure of the disorder or randomness of a system gt It is a state function which means that it depends on pressure volume and temperature gt It is also an extensive property which means that it is dependent on the amount of material in the system gt Its SI unit is JK gt The SI unit for molar entropy is JKmol Entropy Change AS gt The change is only dependent on the initial and final states d Igt When the temperature Is not constant ASjlgfz gt Ebr constant temperature A5222Z gt ExpansionCompression Ebr an ideal gas changing volumes isothermally V P AS nR 1n 2 or AS nR1n 1 V1 P2 39Ebr an expansion entropy change is positive 39Ebr a compression entropy change is negative gt Surroundings As ma 39 AS wrJggrrigg The temperature is the same for the system and surroundings 3gt Reversible Change In State Q Q ASSyS 117 q q z Assurr 517 7617 9 ASuniv A5315 Assurr 6111 O gt Irreversible Change In State Q Q ASSyS 117 q q w w z Assurr 5 139 1139617 7317617 lgf39ev q w w w z Asuniv ASSyS Assurr 117 l139 17 Trev 1361 gt Expansion wKw wHEM and are both along with wh137are all negative values v39This leads to ASumV being positive because the absolute value of WNW is greater than wnmmh v ASmuv is zero for a reversible reaction and positive for an irreversible spontaneous reaction Entropy Change Due To Mixing Of Ideal Gases 339 nAVA at PT and nBVB at PT 9 n nA nB V VA VB at PTW V V 339 AS ASA ASB ASAnAR1n ASBnBR1n VA VB VA 11A V 1 xA V Tl VA XA Entropy Change Due To HeatingCooling T few 39AS 1 when volume is constant 1 T39EdT 39If n is constant ASnj 1 T1 T 339 If CV is constant AS nCV fTZEdT nCVlnT 2 1 1 T2 TIC 3913 T1 T At constant pressure AS AS nip f 2dT nip 1n T2 EPdT AS 11le T Entropy Change For Phase Transition All at constant temperature and pressure g Agzz zz zz T T T Absolute Entropy And The Third Law Of Thermodynamics Entropy OfA State gt gt S If Wl k3 lnW SO Wthe number of microstates The Third Law Of Thermodynamics gt 7 V V7 V7 The entropy of perfect crystals of a pure element or compound is zero at absolute zero because it can only make one microstate SOO At constant pressure ASnf zdT or A5 2dT If T1OK T2T T 0 2 de or 522 de If T1298K T2T T 298 2de For a general reaction written as aA bB cC dD ASTA5298fT A dT this can also be used for standard 23T state conditions A52098 C52098C d52098D a52098A 19520983