Studies On The Thermodynamic Properties Of Compounds: Langbeinite-Type Double Sulfate Salts, Maleic Acid Complexes, Ethane And Ethyl Radical

Studies on the thermodynamic properties of compounds: langbeinite-type double sulfate salts, maleic acid complexes, ethane and ethyl radical have been summarized in the present dissertation.In the first part of the present dissertation, experimental studies on thermodynamic properties of titled molecules have been summarized. The standard molar formation enthalpies of (A+)2Cd2(SO4)3 [A+ is NH/ or K"^ and K2Zn2(SO4)3are determined from the enthalpies of dissolution (A5//m) of [(A^)2SO4 (S) +2CdSO4 (S)] and (A+)2Cd2(SO4)3 (S) in double distilled water or 3 mol-L"1 HN03solvent respectively, at 298.2 K, as AfHm9 [(NH4)2Cd2(SO4)3, S, 298.2K] = -3031 .74 kJ-mol'1, AfHm'[K2Cd2(SO4)3, S, 298.2K] = -3305.52 kJ-mol'1, and AfHm9[K2Zn2(SO4)3, S, 298.2K] = -3406.85 kJ-mol'1.The formation reactions of the complexes formed between zinc (II), and nickel (II) with maleic acid (C4O4H4), i.e., M(OH)2 (s) + C^FL, (s) -> M(C4O4H2)-2H2O2+ 2+(s) (M=Zn and Ni ), have been thermo-chemically studied. The molar dissolution enthalpies of the reactants and products in the above-given reactions were measured, respectively, in a certain solvent (1 mol-L HNO3) by using an isoperibol calorimeter at 298.2 K. The standard molar formation enthalpies of2+ 2+M(C4O4H2)-2H2O (s) (M=Zn and Ni ) were experimentally determined with theauxiliary thermal data and appropriate thermo-chemical cycles:A,//* ( Zn(C404H2>2H2O, S, 298.2 K) = -1436.74 ? 0.042 kJ - mol"', andA/^(Ni(C404H2>2H2O, 8,298.2 K) = -1212.30 ? 0.126 kJ ?mof'.In the second part of the present dissertation, theoretical studies on thermodynamic properties of molecules have been summarized. A model chemistry is a theoretical construct that is used in estimating the structure, energy, and other properties of molecules. The G2 model developed by Pople et al. is an example of a well-studied model chemistry that has been applied with much success to a variety of chemical problems. A different approach has been taken by Ochterski et al., by making use of a complete basis set (CBS) extrapolation of the second-order energy. CBS models take advantage of the fact that order-by-order contributions to chemical energies, and thus the number of significant figures required for a given accuracy, generally decrease with increasing order of perturbation theory. Concomitantly, the computational demands increase rapidly for the higher orders of perturbation theory. These two complementary trends were combined to design two efficient computational models which employ progressively smaller basis sets for the higher orders of perturbation theory.The less computationally intensive of the two models is CBS-4 which is practical for up to 12 non-hydrogen atoms. CBS-4 method has been employed to theoretically study the thermodynamic property of maleic acid molecule.The CBS-Q model uses larger basis sets at every level of theory and its practical for systems with up to six non-hydrogen atoms. CBS-Q has been employed to theoretically study the thermodynamic properties of each of the reactants and products in the reaction where ethyl radical abstracts a hydrogen atom from molecular hydrogen.