Topic
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.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this article, light scattering was used to determine the dependence of the critical micelle temperature on concentration for solutions of a polystyrene-block-poly(ethylene/propylene) copolymer in n-hexane, n-heptane and n-decane.
Abstract: Light scattering was used to determine the dependence of the critical micelle temperature on concentration for solutions of a polystyrene-block-poly(ethylene/propylene) copolymer in n-hexane, n-heptane, n-oxtane, n-decane, and n-dodecane. The results were used to estimated the standard Gibbs energy, ΔG°, the standard enthalpy, ΔH°, and the standard entropy, ΔS°, of micellation. The values of ΔH° were large and negative and were markedly dependent on the carbon number of the lower n-alkanes. The values of ΔG° are negative for all n-alkanes studied
37 citations
TL;DR: In this paper, the density and surface tension of the ionic liquid (IL) [C2mim][B(CN)4] (1-ethyl-3-methylimidazolium tetracyanoborate) were measured in a temperature range from (283.15 to 338.15) K.
Abstract: The density and surface tension of the ionic liquid (IL) [C2mim][B(CN)4] (1-ethyl-3-methylimidazolium tetracyanoborate) were measured in a temperature range from (283.15 to 338.15) K. In terms of Glasser’s semiempirical relation of ILs, the standard molar entropy and the lattice energy of the homologous series of ILs [Cnmim][B(CN)4] were estimated, respectively. Using Kabo’s method and Rebelo’s method, the molar enthalpy of vaporization of [C2mim][B(CN)4], ΔlgHm0 (298 K), at 298 K, and ΔlgHm0 (Tb), at hypothetical normal boiling point, Tb = 680 K, was estimated, respectively. According to the interstice model, the thermal expansion coefficient of [C2mim][B(CN)4], α = 4.77·10−4 K−1, was estimated and was in good agreement with experimental value.
37 citations
TL;DR: In this article, the adsorption data of Gorbach et al. were re-analyzed and model isotherms were derived considering a two site hypothesis, one for α cage and one for β cage.
Abstract: The adsorption data of Gorbach et al. (Adsorption 10(1): 29–46, 2004) and Morris (J. Colloid Interface Sci. 28: 149–155, 1968) for the adsorption of water on 4A zeolite pellets is re-analyzed. Model isotherms are derived considering a two site hypothesis, one for the α cage and one for the β cage. Four simple model isotherms are fitted to the data. Both a dual site Toth or dual site Langmuir isotherm model fit the data adequately. The optimized standard enthalpy and entropy of adsorption parameters derived from the data are surprising for the β cage. The optimized standard enthalpy of the β cage is 1/3rd of that observed calorimetrically, and the standard entropy of adsorption is positive, a physical impossibility. Substituting the calorimetric enthalpy of adsorption corrected the standard differential entropy of sorption values resulting in the standard entropy of sorption values varying significantly with temperature. This variation is postulated to be due to either water of hydration formation, or clathrate formation, or the formation of clusters of water such as dimers, trimers, etc.
36 citations
TL;DR: In this article, the low-temperature heat capacities of BaCeO 3 have been measured from 5 to 370 K by adiabatic calorimetry, and the hightemperature enthalpy increments from 510 to 940 K by drop-calorimetric methods.
36 citations
TL;DR: In this paper, the authors used ultrahigh vacuum techniques to measure the equilibrium pressure of hydrogen dissolved in niobium in dilute solutions over the pressure, concentration and temperature ranges, pe=10-7-10-2 Torr, H/Nb=0-0.035, and T=351-487 K. The rate limiting process is identified as the recombination of hydrogen atoms on the metal surface rather than diffusion within the bulk provided the overall concentration is less than H/nb approximately=0.02.
Abstract: Ultrahigh vacuum techniques have been used to measure the equilibrium pressure of hydrogen dissolved in niobium in dilute solutions over the pressure, concentration and temperature ranges, pe=10-7-10-2 Torr, H/Nb=0-0.035, and T=351-487 K. Sievert's law which indicates ideal solution behaviour was observed for hydrogen concentrations below about H/Nb=0.023; the solubility data are described by the expression square root pe=c(395.4+or-33.8)exp(-(4.345+or-0.161)*103/T) where c=H/Nb*100. The standard partial molar entropy and enthalpy of solution are Delta s0=49.6+or-2.3 J K-1 g-atom-1 and Delta h0=-36.12+or-1.34 kJ g-atom-1. The value of Delta s0 is compared with theoretical entropies calculated from configurational and vibrational contributions. The rate of evolution of hydrogen from a niobium filament has been studied over the pressure and temperature ranges 10-7-10-3 Torr and 465-553 K. The rate limiting process is identified as the recombination of hydrogen atoms on the metal surface rather than diffusion within the bulk provided the overall concentration is less than H/Nb approximately=0.02. The activation energy for the process is 67.56+or-1.26 kJ mol-1.
35 citations