Thermodynamic properties of vapor complex Na2ZrCl6

Thermodynamic studies were carried out for the vapor complex of sodium chloride with zirconium tetrachloride at 718–778 K and 0.5–2.5 kPa by using high temperature phase equilibrium-quenching experiments, taking closed Pyrex glass ampoules as the reaction containers. The results show that the sole predominant vapor complex is Na2ZrCl6 for the ZrCl4-NaCl system under the experimental conditions. The thermodynamic equilibrium constants and other thermodynamic functions of the reaction 2NaCl(s)+ZrCl4(g)=Na2ZrCl6(g) have been derived from the measurements. The results for the changes in enthalpy and entropy are ΔH0=(−70.1±1.5) kJ/mol and ΔS0=(−105.9±2.0) J/(mol·K) in the temperature range.