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4826165 
Journal Article 
Low-Temperature Heat Capacities and Standard Molar Enthalpy of Formation of Potassium Hydrogen Phthalate C8H5KO4(s) 
Kong, YuXia; Di, YouY; Xu, Yan; Yang, WeiWei; Tan, ZhiC 
2010 
Yes 
Journal of Chemical and Engineering Data
ISSN: 0021-9568
EISSN: 1520-5134 
55 
6 
2185-2191 
WOS:000278480500019 
Potassium hydrogen phthalate (KHP) was synthesized by the method of liquid-phase synthesis, in which phthalic acid and potassium hydroxide were chosen as the reactants. The structure and composition of the compound were characterized by chemical and elemental analyses, X-ray powder diffraction, and X-ray crystallography. Low-temperature heat capacities of the compound were measured by a precision automated adiabatic calorimeter over the temperature range from (78 to 400) K. A polynomial equation of the heat capacities as a function of the temperature was fitted by a least-squares method. The smoothed heat capacities and the thermodynamic functions of the compound relative to 298.15 K were calculated and tabulated at an interval of 5 K. In accordance with Hess' law, a thermochemical cycle was designed. The enthalpy change of the reaction of phthalic acid with potassium acetate was determined to be Delta H-r(m)o = -(4.298 +/- 0.493) kJ.mol(-1) by use of an isoperibol solution-reaction calorimeter, and the standard molar enthalpy of formation of C8H5KO4(s) was calculated to be Delta H-f(m)o(C8H5KO4, s) = (1028.05 +/- 0.61) kJ.mol(-1) by use of the enthalpies of dissolution and other auxiliary thermodynamic quantities.