Thermochemical and Theoretical Investigations of the Sodium-Oxygen System. I. The Standard Enthalpy of Formation of Sodium Oxide (Na2O)

Abstract

Calorimetric measurements of the enthalpy of hydrolysis of pure sodium oxide (Na2O) are described. Based on the enthalpy of reaction, the standard enthalpy of formation at 298.15°K, Δ Hf298o(Na2O), was calculated to be −414.82± 0.28 kJ mole−1 (−99.14± 0.07 kcal mole−1). The enthalpy of reaction reported in the present study is significantly more exothermic than that determined by previous investigators. This discrepancy is attributed to the probable presence of hydroxide, carbonate, or other contaminants in the earlier sodium oxide samples.