Enthalpy of formation of zinc acetate dihydrate

Abstract

The enthalpy of formation of zinc acetate dihydrate (Zn(CH 3COO) 2 · 2H 2O) was measured with respect to crystalline zinc oxide (ZnO), glacial acetic acid (CH 3COOH) and liquid water by room temperature solution calorimetry. The enthalpy of formation was verified by utilizing two independent thermodynamic cycles, using enthalpy of solution measurements in 5 mol · L −1 sodium hydroxide (NaOH) and in 5 mol · L −1 hydrochloric acid (HCl) solutions. The enthalpy of the reaction ZnO (cr) + 2CH 3COOH (l) + H 2O (l) to form Zn(CH 3COO) 2 · 2H 2O (cr) is –(65.78 ± 0.36) kJ · mol −1 for measurements in 5 mol · L −1 NaOH and –(66.25 ± 0.17) kJ · mol −1 for measurements in 5 mol · L −1 HCl. The standard enthalpy of formation of Zn(CH 3COO) 2 · 2H 2O from the elements is –(1669.35 ± 1.30) kJ · mol −1. This work provides the first calorimetric measurement of the enthalpy of formation of Zn(CH 3COO) 2 · 2H 2O.