Heats of reaction at constant volume

For the dependence of the heat of reaction at constant volume, we have Kirchhoff s equation ( 58) ... 

Exercise 3.33. Show that the difference between the heats of reaction at constant volume and constant pressure is dRT for a reacting mixture of ideal gases. 

If any of the reactants or products of the calorimetric reaction are gaseous, it is necessary to conduct the reaction in a sealed bomb. Under this condition the system is initially and finally in a constant volume rather than being under a constant pressure. The measured heat of reaction at constant volume is equal to an energy increment, rather than to an enthalpy increment ... 

This shows the relation between the change in free energy, or the chemical affinity of a reaction, the heat of reaction at constant volume, the absolute temperature at which the reaction proceeds, and the temperature coefficient of the chemical affinity, dAjdTj of the reaction. These three... 

These two energies of activation are related to the heat of reaction (at constant volume) by the formula... 

As the heat of reaction at constant volume is equal to the difference between internal energy at the beginning and the end of the transformation, and the effect of reaction heat at constant pressure is equal to the difference between enthalpy at the beginning and the end of the transformation, respectively the heat of reaction is independent of the pathway, and is only a function of the initial and hnal state. This proposal is called Hess s law, which enables the indirect determination of the total heat effect of the reactions chain by knowing separately the reaction heats for each reaction in the chain. 

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