A novel compound - monohydrated cupric nicotinate was synthesized by solid phase synthesis at room temperature. FTIR, chemical and elemental analyses, and X-ray powder diffraction technique were applied to characterize the structure and composition of the complex. Enthalpies of dissolution of {Cu(Ac)2 H2O(s)} and {HAc(l)} in 0.1 M HCl solution, {Nic(s)} in 0.1 M HCl solution containing certain amounts of monohydrated cupric acetate, and {Cu(Nic)2 H2O(s)} in 0.1 M HCl solution containing certain amounts of acetic acid at T = 298.15 K were determined by means of an isoperibol solution-reaction calorimeter: DsHCu(Ac) H O o2 2 = -(6.234 ± 0.187) kJ mol-1, DsHHAc o = -(1.788 ± 0.008) kJ mol-1, Ds HNico± = (10.337 ± 0.393) kJ mol-1, and DsHCu(Nic) H Oo2 2 = -(6.801 ± 0.130) kJ mol-1. In accordance with Hess law, a reasonable thermochemical cycle was designed, the enthalpy change of the solid phase reaction of monohydrated cupric acetate with nicotinic acid was determined to be DrHmo = (24.817 ± 0.818) kJ mol-1, and the standard molar enthalpy of formation of the title complex was found to be -(891.463 ± 2.139) kJ mol-1.
Molar enthalpies of dissolution of {ZnSO4×7H2O(s) + 2NaNO3(s) + L-AA(s)} (in which AA stand for phenylalanine, histidine and methionine) in 100 cm3 of 2 mol×dm-3 HCl at T = (298.15 š 0.001) K have been measured to be deltaHm,1 o = (69.417 š 0.051) kJ×mol-1, (79.830 š 0.058) kJ×mol-1, and (56.929 š 0.051) kJ×mol-1, respectively, by means of an isoperibol solution-reaction calorimeter. Molar enthalpies of dissolution of {Zn(AA)(NO3)2×xH2O(s) + Na2SO4(s)} (in which x = 1 for phenylalanine, x = 1/2 for histidine and methionine) under the same conditions have been determined to be deltaHm,2 o = (48.137 š 0.038) kJ×mol-1, (51.146 š 0.041) kJ×mol-1, and (37.337 š 0.029) kJ×mol-1, respectively, using the calorimeter. The standard molar enthalpies of formation of these complexes Zn(AA)(NO3)2×xH2O(s) have been derived to be delta fHm o [Zn(Phe)(NO3)2×H2O, s, 298.15 K] = -(1367.07 š 3.52) kJ×mol-1, delta fm o [Zn(His)(NO3)2×1/2H2O, s, 298.15 K] = -(1207.19 š 2.82) kJ×mol-1, and delta fHm o [Zn(Met)(NO3)2×1/2H2O, s, 298.15 K] = -(1327.08 š 0.75) kJ×mol-1, respectively, by the combination of the experimental values of enthalpies of dissolution with some auxiliary thermodynamic data through a designed Hess thermochemical cycle on the basis of a supposed chemical reaction.
A new compound (NaCuAsO4×1.5H2O) was synthesized, and its composition was determined by means of the methods of ignition loss-in-weight and chemical analysis. The standard molar enthalpies of dissolution of the mixtures {Na3AsO4×12H2O(s) + CuSO4×5H2O(s)} and {NaCuAsO4×1.5H2O(s) + Na2SO4(s)} in 1.498 mol×dm–3 HCl so lu - tion at 298.15 K have been determined to be respectively Ds m. H 1 0 = (64322 š 63) J×mol–1 and Ds m. H 2 0 = –(20558 š 25) J×mol–1 using an isoperibol solution-reaction calorimetry. From these values and other thermodynamic data, the standard molar enthalpy of formation of NaCuAsO4×1.5H2O(s) has been de rived: Df m H0 (NaCuAsO4×1.5H2O, s, 298.15 K) = –(1469.33 š 0.65) kJ×mol –1. In addition, UV/Vis spectra and refractive in dexes of solution A and solution A’ were measured to examine the reliability of the designed thermodynamic cycle.
The energies of combustion in fluorine of three specimens of hexagonal boron nitride with different degree of ideal crystalline structure have been measured in a twocompartment calorimetric bomb at 298.15 K according to reaction: BN(cr) + 3/2F2(g) = BF3(g) + 1/2N2(g), and new standard molar enthalpies of formation f m H0 have been calculated and used to rank the samples in order of stability: f m H0 = -(245.8š1.1) kJ/mol for turbostratic sample, that deviates most from the crystalline structure; f m H0 = -(248.5š0.9) kJ/mol for the sample with an interlayer spacing that is only about 0.5% larger than the ideal crystalline h-BN; and f m H0 = -(250.8š1.2) kJ/mol for crystalline h-BN.
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