Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

Low-temperature heat capacities of sodium 5-nitroisophthalic acid monohydrate (C8O6NH3Na2*H2O, s) were measured by a precision automated adiabatic calorimeter over the temperature range from (78 to 398) K. The experimental values of the molar heat capacities were fitted to a polynomial equation of heat capacities (Cp,m) with the reduced temperatures (X), [X = f(T)], by a least-squares method. The smoothed molar heat capacities and thermodynamic functions of the compound (C8O6NH3Na2*H2O, s) were calculated on the basis of the fitted polynomial. The constant volume energy of combustion of the compound at T = 298.15 K was measured by a precise rotating-bomb combustion calorimeter to be ?cU = -(3969.41 +- 1.74) kJ*mol-1. The standard molar enthalpy of combustion of the compound was determined to be ?cH?m = -(3965.07 +- 1.74) kJ*mol-1. The standard molar enthalpy of formation of the compound was calculated to be ?fH?m (C8O6NH3Na2*H2O, s) = -(408.45 +- 2.03) kJ*mol-1 in accordance with Hess s law. The standard molar enthalpy of solution of the compound, ?solH?m (C8O6NH3Na2*H2O, s), has been determined as (22.133 +- 0.111) kJ*mol-1. The standard molar enthalpy of the hydrated anion of the compound was determined as ?fH?m (C8O6NH32-, aq) = (380.11 +- 2.04) kJ*mol-1, from the standard molar enthalpy of solution and other auxiliary thermodynamic data through a thermochemical cycle. The thermostability of the compound was investigated by thermogravimetric/differential thermogravimetric/differential scanning calorimetry (TG-DTG-DSC).