Standard molar entropy

About: Standard molar entropy is a research topic. Over the lifetime, 1586 publications have been published within this topic receiving 29886 citations.

Predictive thermodynamics for ionic solids and liquids

Abstract: The application of thermodynamics is simple, even if the theory may appear intimidating We describe tools, developed over recent years, which make it easy to estimate often elusive thermodynamic parameter values, generally (but not exclusively) for ionic materials, both solid and liquid, as well as for their solid hydrates and solvates The tools are termed volume-based thermodynamics (VBT) and thermodynamic difference rules (TDR), supplemented by the simple salt approximation (SSA) and single-ion values for volume, Vm, heat capacity, , entropy, , formation enthalpy, ΔfH°, and Gibbs formation energy, ΔfG° These tools can be applied to provide values of thermodynamic and thermomechanical properties such as standard enthalpy of formation, ΔfH°, standard entropy, , heat capacity, Cp, Gibbs function of formation, ΔfG°, lattice potential energy, UPOT, isothermal expansion coefficient, α, and isothermal compressibility, β, and used to suggest the thermodynamic feasibility of reactions among condensed ionic phases Because many of these methods yield results largely independent of crystal structure, they have been successfully extended to the important and developing class of ionic liquids as well as to new and hypothesised materials Finally, these predictive methods are illustrated by application to K2SnCl6, for which known experimental results are available for comparison A selection of applications of VBT and TDR is presented which have enabled input, usually in the form of thermodynamics, to be brought to bear on a range of topical problems Perhaps the most significant advantage of VBT and TDR methods is their inherent simplicity in that they do not require a high level of computational expertise nor expensive high-performance computation tools – a spreadsheet will usually suffice – yet the techniques are extremely powerful and accessible to non-experts The connection between formula unit volume, Vm, and standard thermodynamic parameters represents a major advance exploited by these techniques

Adsorption of aromatic compounds in large MFI zeolite crystals

Abstract: Very large (180 × 40 × 40 µ3) and well defined crystals have been used in a gravimetric system to investigate the adsorption of aromatic compounds in MFI (silicalite) zeolite. The isotherms and isosteric heats of adsorption (Qst) were reported for future comparison with various adsorption models. Three types of phase transition were found. Isotherms of p-xylene showed a sharp step rise from ca. 4 to 8 molecules uc–1. A clear phase boundary could be outlined. Adsorbed benzene behaved as a dual-phase system in the range between 4.6 and 6 molecules uc–1. There were more phase transitions above 6 molecules uc–1 but it was not possible to outline the phase boundary. Molar entropy changes of 210 and 180 J mol–1 K–1 were found for the observed p-xylene–MFI and benzene–MFI phase transitions. For ethylbenzene and toluene, a dual-phase region was also observed but the transition was less pronounced. Isosteric heats, calculated from isotherms, showed a complex variation with loading and a strong dependence on temperature. It was also found that the adsorption kinetics are strongly influenced by the previous adsorption history. For freshly calcined samples the uptake rate was relatively fast. However, re-calcination after the adsorption of p-xylene created a diffusion barrier inside the crystalline material and subsequent adsorption of other aromatic compounds became much slower and displayed two-step kinetics.