Thermodynamic properties of RuSe 2 from 5 to 1500 K

Abstract

The heat capacity of RuSe 2 has been measured in the range from 5 to 988 K with adiabatic low- and high-temperature calorimeters. From 882 to 1483 K a drop calorimeter was used to measure enthalpy increments of the compound. Thermodynamic functions have been calculated. Values at 298.15 and 1500 K of the molar heat capacity C p,m , standard molar entropy Δ 0 T S m o( T), and standard molar function Φ m o( T,0) are 69.87, 80.084, 36.407 J · K −1 · mol −1, and 90.45, 205.77, 132.86 J · K −1 · mol −1, respectively. Decomposition pressures for the reaction: RuSe 2(s) = Ru(s) + Se 2(g), have been determined between 1270 and 1480 K by means of a Bodenstein-type silica-glass manometer. The results obtained by the static measurements extend the torsion-effusion measurements accomplished by Murray and Heyding at lower temperatures. The standard molar enthalpy formation for RuSe 2 from Ru(s) and Se(s, hex) at 298.15 K is −(162.07±0.72) kJ·mol −1 according to the third-law treatment. The uncertainty given is one standard deviation.