Enthalpy differential

Fig. 2.11 Curves of the differential enthalpy of adsorption of nitrogen against surface coverage 0 (= for samples of Sterling carbon black heated at the following temperatures (a) 1500°C (fc) 1700°C (c) 2200 C (d) 2700°C. The curve for 2000°C was similar to (c). but with a lower peak. The calorimetric temperature was 77-5, 77-7, 77-4, 77-4 K in (a), (fc), (c) and (d) respectively.

Fig. 5. Differential enthalpy of ionization of crosslinked MA-DMEG copolymers as a function of the degree of ionization of carboxylic groups. Crosslinking agent (DMEG) content (mol%) 1)3 2) 7.5 5) 12...

Table 10. Change in differential enthalpy in the interaction between Hb and CP at different degrees of CP filling with protein (Y)...

Solution In this example, it is assumed that we add a solute to a large enough volume of solution so that the composition of the mixture does not change. The enthalpy change for this process is referred to as a differential enthalpy of solution. We can represent this process by... 

Differential enthalpies of exchange, plotted as a function of K saturation, exhibit a stepped character (Figure 1 and Table II). This can only reflect different types of adsorption sites on the clay surfaces, the group of sites with the most negative enthalpy... 

Table III. Groups of exchanqe sites in some <0. vm montmorilIonites as distinguished by differential enthalpies of exchanqe. ( >om reference 11)...

Differential enthalpy values (k[Pg.336]

Table IV. Groups of exchange sites in some <5 pm kaolins as distinguished by differential enthalpies of Ca + 2K exchange. (From reference 12J...

Figure 2. The differential enthalpy of Ca 2K exchange (d(AHx/dx) as a function of fractional K saturation for the Batcombe series soils from various plots of the Broadbalk Classical Experiment at Rothamsted. 

The site-selectively derived thermodynamic parameters obtained by adaptation of Equation 1.17 (Table 1.8) clearly revealed that the heat of adsorptions are exothermic on both enantioselective and nonenantioselective sites, and the difference in the adsorption enthalpies on enantioselective and nonenantioselective sites is about 10 and 15 kJ mol for/ - and 5-enantiomers, respectively. The differential enthalpy change upon adsorption of R- and 5-enantiomers at the enantioselective site AAEIg... 

The ratio of the amount of heat evolved for each increment to the number of moles adsorbed (in the same period) is equal to the average value of the differential enthalpy of adsorption in the interval of the adsorbed quantity considered. The curve showing the differential heat variations in relation to the adsorbed amount is traditionally represented by histograms. However, for simplification, the histogram steps are often replaced by a continuous curve connecting the centers of the steps. 

We turn now to the comparison of solid c/s-cyclopropane-l,2-dicarboxylic acid82 (20b, X = COOH) and its benzene relative, phthalic acid (47a, X = COOH). The difference of enthalpies of formation is 17 kJ mol 1, a number that needs to be corrected by enthalpies of sublimation to the desired gas-phase difference. Neither datum is available from experiment83. If we equate differential enthalpies of sublimation and of vaporization—a highly suspect approach, but what can we use that is better84 we deduce <529(Phv°, Cyprv COOH) is ca 31 kJ mol. Recall that the value for the rather much related <5,9(Ph, Cypr COOMe) was ca 20 kJ mol 1. Are the results consonant Given all of our assumptions, we are not that wrong. 

Differential) enthalpy of adsorption on uncovered surface — q° Transfer coefficient a... 

Differential enthalpy changes of hydrogen and isobutylene adsorption were measured, as described elsewhere (36, 42). Figure 3 shows differential heat versus adsorbate coverage for hydrogen and isobutylene adsorption on Pt/Sn/Si02. Values of the differential enthalpy changes of adsorption,... 

Much of the early studies of surfactant adsorption at the solid-solution interface were based on classical experimental techniques, such as solution depletion [1, 32], fluorescence spectroscopy [2], and measurements of the differential enthalpy of adsorption [2], Such methods have provided much of the basic initial understanding. However, they provide no direct structural information and are difficult to apply to mixtures [23, 34], However, when combined with other techniques, such as NMR and flow microcalorimetry, they provide some insight into the behaviour of mixtures. This was demonstrated by Thibaut et al. [33] on SDS/C10E5 mixtures adsorbed onto silica and by Colombie et al. [34] on the adsorption of SLS/Triton X-405 mixtures onto polystyrene particles. 

The differential enthalpies can be deduced either by differentiation of the integral enthalpy with respect to the amount of each component or from the expressions for the corresponding differential free energies. The partial molal enthalpy of the adsorbent is... 

---