Chemical Thermodynamics Heat transfer battery Heat transfer, q, can - PowerPoint PPT Presentation

Chemical Thermodynamics

Heat transfer battery Heat transfer, q, can be measured  through calorimetry. Load bomb  Measure T init  Ignite  Measure T final  Constant Volume  Chemical Thermodynamics CEM 484 2

Heat transfer However, most chemistry is performed at constant  pressure. Introduce enthalpy, H  Chemical Thermodynamics CEM 484 3

Heat transfer Enthalpy is a state function  Evaluate in a similar manner as internal energy U.  Chemical Thermodynamics CEM 484 4

Partial derivative Certain partial derivatives in D U and D H are not  tabulated To evaluate we need more information; 2 nd law, G  and A Chemical Thermodynamics CEM 484 5

Spontaneous Process Isothermal expansion of an ideal gas  P ext P ext Chemical Thermodynamics CEM 484 6

Spontaneous Process 2 nd Law and entropy  Differential form  Chemical Thermodynamics CEM 484 7

Entropy Internal energy and entropy  Differential form  Chemical Thermodynamics CEM 484 8

Enthalpy and Entropy Enthalpy and entropy  To determine whether process is allowed need to  know entropy change of universe Chemical Thermodynamics CEM 484 9

Gibbs Free energy Gibbs free energy, G  Need to restrict to constant pressure  Chemical Thermodynamics CEM 484 10

Helmholtz Free energy Helmholtz free energy, A  Need to restrict to constant volume  Chemical Thermodynamics CEM 484 11