Experimental Determination of the Standard Enthalpy of Formation of Trimellitic Acid and Its Prediction by Supervised...

The standard molar enthalpy of formation for trimellitic acid (TMAc) in the crystalline phase at 298.15 K, Δ_fH°(cr), was calculated experimentally from the enthalpy of combustion through combustion calorimetry experiments. Likewise, the standard molar enthalpy of sublimation was determined from the standard molar enthalpy of fusion and from the standard molar enthalpy of vaporization from differential scanning calorimetry and thermogravimetry, respectively. Subsequently, the standard molar enthalpies of formation in the gas-phase at 298.15 K, Δ_fH°(g), were calculated. The enthalpies of formation for TMAc, hemimellitic, and trimesic acids were predicted using multiple linear regression (MLR) with a nonreplacement evaluation technique. MLR was applied to the data set that allowed estimating these thermochemical properties with an R² greater than 0.99. This model was used to compare the predicted and experimental results for benzene carboxylic acids.