Experimental methods for isothermal calorimetric reaction data

1 Experimental methods for isothermal calorimetric reaction data 

As indicated in Equation 8.3, qtot is not generally simply equal to the reaction heat-flow rate qReact (see Equation 8.4) but is affected by other physical or chemical processes which have heat changes, e.g. mixing or phase changes. As will be shown in Section 8.3, even for a simple reaction such as the hydrolysis of acetic anhydride, a significant heat of mixing occurs which must be taken into account. Furthermore, it should always be kept in mind that the qtot values determined by a reaction calorimeter also contain measurement errors such as base line drifts, time distortions or ambient temperature influences. 

First we will discuss measurement methods that do not require postulation of a reaction model such as the determination of the reaction enthalpy by integration of qt01, which is the simplest of the model-free methods that still leads to a physically meaningful result. The 

For demonstration purposes, we shall assume here that the values of Qm x, Qphase and Qprror are negligible, meaning that qtot = c/React- Furthermore, the reaction is assumed to take place in one single step. If these assumptions are valid, the reaction enthalpy Ar H can be calculated directly by Equation 8.12  

This thermal conversion can be compared to the chemical conversion of the investigated reaction as long as the assumptions mentioned above are valid, or the correspondence b etween chemical and thermal conversions has been verified by another analytical technique. 

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