Molecular models for the solvation of small ions and polar molecules

The Determination of Absolute Values of Entropies of Hydration [ΔSabs0(H+)h]$[\Delta S_{abs}^0{({H^ + })_h}]$ and Aquation [ΔSabs0(H+)aq]$[\Delta S_{abs}^0{({H^ + })_{aq}}]$ and The Thermodynamics of Proton in Solutions

Absolute entropy value of H+ ion i.e. Δ S aq 0 ( H + ) = −   22.2   J K − 1 mol − 1 $\Delta {\rm{S}}_{{\rm{aq}}}^0({{\rm{H}}^ + }) = - \;22.2{\rm{ }}J{K^{ - 1}}{\rm{mo}}{{\rm{l}}^{ - 1}}$ in aqueous solution, a fundamental parameter of importance was determined using a number of extrathermodynamic assumptions of doubtful validity. The value can in no way be regarded to be absolute or correct and needs reassessment. However, no value of the entropy change due to hydration Δ S h 0 ( H + ) $\Delta {\rm{S}}_{\rm{h}}^0({{\rm{H}}^ + })$ was available. Absolute values for entropy of hydration [ Δ S abs 0 ( H + ) h ] $[\Delta {\rm{S}}_{{\rm{abs}}}^0{({{\rm{H}}^ + })_{\rm{h}}}]$ (entropy change for the transfer of H+ ion from gaseous (g) state to H+ ion in aqueous solution) or entropy of aquation [ Δ S abs 0 ( H + ) aq ] $[\Delta {\rm{S}}_{{\rm{abs}}}^0{({{\rm{H}}^ + })_{{\rm{aq}}}}]$ (entropy change for transfer of H(g) to aqueous H ion + ) ${\rm{H}}_{{\rm{ion}}}^ + )$ of H+ ion can only be calculated if the related absolute values of Gibbs energy or enthalpy changes of H+ ion i.e. [ Δ G abs 0 ( H + ) h or aq $[\Delta {\rm{G}}_{{\rm{abs}}}^0{({{\rm{H}}^ + })_{{\text{h or aq}}}}$ and Δ H abs 0 ( H + ) h or aq ] $\Delta {\rm{H}}_{{\rm{abs}}}^0{({{\rm{H}}^ + })_{{\text{h or aq}}}}]$ are known. Critical analysis of the methods used for evaluation of thermodynamics of H+ ion was made. Analysis of the methods showed that the methods had limitations due to defective use of Born equation and ionic additivity principle. Reference electrolyte method using TATB (tetraphenyl arsonium tetraphenyl borate, Ph4AsBPh4), Halliwell and Nyburg’s method and Noyes method or modified Noyes method of Lahiri do not give entropy values. Cluster-ion approximation method (used by Coe and co-workers) gives Δ H abs 0 ( H + ) h $\Delta {\rm{H}}_{{\rm{abs}}}^0{({{\rm{H}}^ + })_{\rm{h}}}$ and Δ G abs 0 ( H + ) h $\Delta {\rm{G}}_{{\rm{abs}}}^0{({{\rm{H}}^ + })_{\rm{h}}}$ and hence Δ S abs 0 ( H + ) h = −   153.0  JK − 1 mol − 1 .   Δ S abs 0 ( H + ) aq $\Delta {\rm{S}}_{{\rm{abs}}}^0{({{\rm{H}}^ + })_{\rm{h}}} = - \;153.0{\rm{ J}}{{\rm{K}}^{ - 1}}{\rm{mo}}{{\rm{l}}^{ - 1}}.\;\Delta {\rm{S}}_{{\rm{abs}}}^0{({{\rm{H}}^ + })_{{\rm{aq}}}}$ is obtained by coupling Δ S abs 0 ( H + ) h $\Delta {\rm{S}}_{{\rm{abs}}}^0{({{\rm{H}}^ + })_{\rm{h}}}$ with Δ S abs 0 ( H + ) g $\Delta {\rm{S}}_{{\rm{abs}}}^0{({{\rm{H}}^ + })_{\rm{g}}}$ [entropy of gaseous H+ ion calculated using Sackur-Tetrode equation], comes out to be –44.2 JK−1mol−1. However, Δ S abs 0 ( H + ) h $\Delta {\rm{S}}_{{\rm{abs}}}^0{({{\rm{H}}^ + })_{\rm{h}}}$ and Δ S abs 0 ( H + ) aq $\Delta {\rm{S}}_{{\rm{abs}}}^0{({{\rm{H}}^ + })_{{\rm{aq}}}}$ determined by Lahiri and co-workers are –50.0 JK−1mol−1 and 20.0 JK−1mol−1. The values can be regarded to be accurate and reliable. Some comments on the surface potential of water towards Δ G h or aq 0 ( H + ) $\Delta {\rm{G}}_{{\text{h or aq}}}^0({{\rm{H}}^ + })$ and error ranges on the energetics of H+ and other ions are given. No attempt was made to determine entropy of hydration or aquation from theoretical calculations.

For1ation of Zeolites: A Molecular Description

Raman spectroscopy of the solution, solid and gel phases present during crystallization of zeolite X was investigated. The vibrational data indicate that an amorphous aluminosilicate solid, composed primarily of four membered aluminosilicate rings is in contact with monomeric silicate ions during the prenucleation stages of the zeolite formation. No intermediate building blocks specific to zeolite X could be discerned from the vibrational spectra. The influence of a series of monovalent cations on the crystallization process was also examined, and a model of zeolite formation has been proposed.

Calculation of Gibbs Energies of Hydration of Monovalent Ions: Examination of Born Equation and its Reevaluation

The limitations of Born equation and its different modifications for the calculation of Gibbs energies of hydration of ions have been briefly reviewed. A modified method for the calculation of hydration energies of ions has been suggested. The hydration energies thus obtained have been compared with the data in the literature.