Isothermal bomb process, internal energy

The experimental data are used to determine the value of A (/(IBP, T2), the internal energy change of the isothermal homb proeess at the final temperature of the reaction. The isothermal bomb process is the idealized process that would have occurred if the reaction or reactions had taken plaee in the calorimeter at constant temperature. 

The internal energy ehange of the isothermal bomb process is corrected to yield A (/(IBP, Tref), the value at the referenee temperature of interest. 

The internal energy change we wish to find is AC/(IBP, T2), that of the isothermal bomb process in which reactants change to products at temperature T2, accompanied perhaps by some further transfer of substances between phases. From Eqs. 11.5.4 and 11.5.5, we obtain... 

The value of A (/(IBP, T2) evaluated from Eq. 11.5.7 is the internal energy change of the isothermal bomb process at temperature T2. We need to correct this value to the desired reference temperature Tref. If T2 and Tref are close in value, the correction is small and can be calculated with a modified version of the Kirchhoff equation (Eq. 11.3.10 on page 323) ... 

The Washburn corrections needed in Eq. 11.5.9 are internal energy changes for certain hypothetical physical processes occurring at the reference temperature T ef involving the substances present in the bomb vessel. In these processes, substances change from their standard states to the initial state of the isothermal bomb process, or change Ixom the final state of the isothermal bomb process to their standard states. 

In the bomb process, reactants at the initial pressure pi and temperature 7 are converted to products at the final pressure pf and temperature Tf. The primary goal of a combustion calorimetric experiment, however, is to obtain the change of internal energy, Ac//°(7r), associated with the reaction under study, with all reactants and products in their standard states pi = pf = O.IMPa) and under isothermal conditions at a reference temperature 7r (usually 298.15 K). Once AC//°(298.15K) is known, it is possible to derive the standard enthalpy of combustion, AC77°(298.15K), and subsequently calculate the standard enthalpy of formation of the compound of interest from the known standard enthalpies of formation of the products and other reactants. 

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