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 ?rHmo = -(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 ?fHmo(C8H5KO4, s) = -(1028.05 +- 0.61) kJ*mol-1 by use of the enthalpies of dissolution and other auxiliary thermodynamic quantities.
Compounds
#
Formula
Name
1
K
potassium
2
C
graphite
3
H2
hydrogen
4
O2
oxygen
5
C8H5KO4
potassium 2-carboxybenzoate
Datasets
The table above is generated from the ThermoML associated json file (link above).
POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied;
the numbers refer to the table of compounds on the left.
Type
Compound-#
Property
Variable
Constraint
Phase
Method
#Points
POMD
5
Molar heat capacity at constant pressure, J/K/mol ; Crystal