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Uses of Cp Equations  H s (298 K) =  H v (298 K) +  H fus (298 K) The fusion, vaporization and sublimation enthalpies of biphenyl are given below. Evaluate.

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Presentation on theme: "Uses of Cp Equations  H s (298 K) =  H v (298 K) +  H fus (298 K) The fusion, vaporization and sublimation enthalpies of biphenyl are given below. Evaluate."— Presentation transcript:

1 Uses of Cp Equations  H s (298 K) =  H v (298 K) +  H fus (298 K) The fusion, vaporization and sublimation enthalpies of biphenyl are given below. Evaluate these thermodynamic properties at T = K and check to see that they are internally consistent.  H s (311 K) = 82.5 kJ mol -1  H v (363 K) = 59.6 kJ mol -1  H fus (341.5 K) = kJ mol -1  H s  = 78.3 kJ mol -1

2 Biphenyl  H s (311 K) = 82.5 kJ mol -1  H s (298 K) =  H s (311 K)+( Cp(c) calc )[ ] Cp(c) calc = 10*17.5+2*8.5 Cp(c) calc = 192 J mol -1 K -1  H s (298 K) = (0.38  0.1)  H s (298 K) = (82.9  0.1) kJ mol -1

3 Biphenyl  H s (298 K) = (82.9  0.1) kJ mol -1  H v (363 K) = 59.6 kJ mol -1  H v (298 K) =  H v (363 K) +( Cp(l) calc )[ ] Cp(l) calc = 10*21.8+2*15.3 Cp(l) calc = J mol -1 K -1  H v (298 K) = (4.88  0.98)  H v (298 K) = (64.5  1.0) kJ mol -1

4 Biphenyl  H s (298 K) = 82.9 kJ mol -1  H v (298 K) = 64.5  1.0 kJ mol -1  H fus (341.5 K) = kJ mol -1  H fus (298 K) =  H fus (341.5 K) +)+[0.15Cp(c) Cp(l)- 9.83][T fus -298]  H fus (298 K) = (1.98  0.6)  H fus (298 K) = (16.7  0.6) kJ mol -1  H s (298 K) = (64.5  1.0) + (16.7  0.6)  H s (298 K) = (81.2  1.2) kJ mol -1

5 NIST Webbook A valuable source of thermochemical information

6 The vaporization enthalpy of anthracene has been measured over the temperature range T = K;  H v =  200 J mol -1. The fusion enthalpy was measured as  H fus (489K) =  100 J mol -1. What is the sublimation enthalpy of anthracene at T = K?

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8 Estimation of Vaporization Enthalpies 1. Group additivity by Guthrie and Taylor Can J. Chem.1983, 61, Group additivity by Ducros, M.; Gruson, J. F.; Sannier, H. Thermochimica Acta 1980, 36, 39-65; Ducros, M., Gruson, J.F., and Sannier, H., Thermochimica Acta, 1981, 44, DuCros, M. Sanier, H. Thermochim. Acta 1982, 54, ; Ducros, M.; Sannier, H. Thermochimica Acta 1984, 75, “Group Additivity” of Chickos, J. S.;Acree, Jr. W. E.; Liebman, J. F. “Computational Thermochemistry”, Irikura, K. K.; Frurip, D. J. Edit. ACS 1996.

9  H v (298) Estimation of Hydrocarbons  H v (298)/kJmol -1 =4.69(n C -n Q )+1.3n Q n Q refers to a quaternary sp3 carbon atom  H v (298)Estimation of Monosubstituted Hydrocarbon Derivatives  H v (298)/kJmol -1 =4.69(n C -n Q )+1.3n Q +3.0+n M M +b +C

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11  H v (298) Estimation of Hydrocarbons Estimate  H v (298) for cycloheptatriene  H v (298)=4.69(n C -n Q )+1.3n Q  H v (298) = 39.4 kJmol -1 (literature) Estimate  H v (298) for 2-nitrotoluene  H v (298) = 59.1 kJmol -1 (literature)

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13  H v (298) Estimation of Polysubstituted Hydrocarbon Derivatives

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15 Estimate  H v (298) of 1,2-dichlorobenzene C 6 H 4 Cl 2 1,2-dichlorobenzene[ ] 51.2(256)[99/20] ( )44.5(376)EB[98/8] ( )50.8(271)[96/19] ( )50.9(298)GC[94/22] ( )51.2GC[94/23] ( )44.0(388)A[87/5] ( )49.9(298)[84/9][91/2] ( )50.0(322)GS[82/1]

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17 Estimate the vaporization enthalpy of perfluoro-2- methylbutane. Estimate the vaporization enthalpy of nonafluorocyclopentane Estimate the vaporization enthalpy of dibutyl disulfide

18 Estimate the vaporization enthalpy of 2-propoxyethanol Estimate the vaporization enthalpy of 2-isopropoxyethanol Estimate the vaporization enthalpy of 2,2-dimethoxypropane


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