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.

Method for the Estimation of Standard Entropy of Crystal Phases at 298.15 K on the Limited Temperature Range of Heat Capacity Measurements

Abstract: A method for estimating entropy of crystal phases at 298.15 K, when a direct calculation from heat capacity data is not possible due to a limited range of temperature for Cp measurements, is proposed. It was shown that a reasonable estimation of So298.15 for the substances with predominant lattice contribution can be achieved by approximation of heat capacities from “nitrogen” to room temperature by the combination of Einstein functions and by correction of the obtained entropy value with the scaling coefficient. The same result can be obtained in the presence of an additional contribution to the heat capacity, connected with the settling of upper energy levels if there are data for a priori estimation of the corresponding contribution.

The heat capacity and standard thermodynamic functions of Ni 0.5 Zr 2 (PO 4 ) 3 phosphate over the temperature range from T→0 to 664 K

Abstract: The temperature dependence of the heat capacity of crystalline nickel zirconium phosphate C°p = f(T) was measured over the temperature range 6–664 K. The experimental data obtained were used to calculate the standard thermodynamic functions of Ni0.5Zr2(PO4)3 from T → 0 to 664 K. The standard entropy of phosphate formation from simple substances at 298.15 K was calculated from the absolute entropy of the compound. The data on the low-temperature heat capacity were used to determine the fractal dimension of Ni0.5Zr2(PO4)3 over the temperature range 30–50 K. Conclusions concerning the heterodynamic characteristics of the structure of Ni0.5Zr2(PO4)3 were drawn.

Thermodynamic study of disorder in hexa-amminenickel(II) iodide and diamminenickel(II) iodide

Abstract: The heat capacity of crystalline nickel(II) iodide, diamminenickel(II) iodide and hexa-ammine-nickel(II) iodide has been determined from 10 to 300 K by conventional adiabatic low-temperature calorimetry, and from 300 to 550 K by differential scanning calorimetry. Measurements have also been made of (a) the heat of solution of the three salts in dilute acid at 298.15 K, (b) the ammonia dissociation pressure for the systems nickel iodide + diamminenickel iodide (from 490 to 523 K) and diamminenickel iodide + hexa-amminenickel iodide (from 469 to 503 K), (c) the magnetic susceptibility of nickel iodide and diamminenickel iodide from 4 to 230 K. The thermodynamic results have been used to obtain for the diammine and the hexammine two values of the molar entropy at 298.15 K, namely the third-law entropy Scal, and the entropy Seq derived from the appropriate equilibrium study. For each salt, Scal and Seq agree within experimental error, so that both salts appear to become completely ordered at 0 K. The implications of this result for hexa-amminenickel iodide are briefly discussed in the light of previous experimental and theoretical work on this salt.