Calcium oxide structure, data

Given that strontium oxide crystallizes with the same structure as calcium oxide, use data tables to estimate the minimum cation/anion distance and hence determine the lattice energy for SrO. 

The crystal of CaO assumes the NaCl structure, the closest approach between positive and negative ions being 239 pm. The enthalpy of atomization of calcium metal is 193 kJ mol that of dioxygen is 248 kJ moT1 (of oxygen atoms). The two electron attachment enthalpies of oxygen are -148 and +838 kJ mol respectively. The first and second successive ionization enthalpies of calcium are 596 and 1156 kJ mol respectively. Use the data to calculate a value for the standard enthalpy of formation of calcium oxide and compare the result with the experimental value of -635 kJ mol... 

Oxidation by direct H transfer from the a-carbon of alcohols to the pyrroloquinoline quinone (PQQ) cofactor of alcohol dehydrogenases was studied using ab initio quantum mechanical methods <2001JCC1732>. Energies and geometries were calculated at the 6-31G(d,p) level of theory, results were compared to available structural and spectroscopic data, and the role of calcium in the enzymatic reaction was explored. Transition state searches at the semi-empirical and STO-3G(d) level of theory provided evidence that direct transfer from the alcohol to C-5 of PQQ is energetically feasible. 

The devices used for the EL and PL measurements were fabricated in the thin film sandwich configuration anode/polymer/cathode. The electronic structure of alkoxy derivatives of PPV has been studied via internal field emission [42], internal photoemission [76], cyclovoltammetric spectroscopy [159]) and photoelectron spectroscopy [160]. The data indicate that the bottom of the Tr -band and the top of the ir-band are at 3 eV and 5 eV respectively, with respect to the vacuum. Thus, relatively good hole and electron injection can be achieved by using transparent indium/tin-oxide (ITO) as the anode and calcium (Ca) or barium (Ba) as the cathode [42,161]. In practice, however, hole injection is very sensitive to the quality of the ITO. A thin layer (= 300 A) of conducting polymer provides excellent, reproducible hole injecting contacts [70,71,162]. 

The XPS analysis of unwashed membranes showed that ESCA could identify the organic fouling layers of the membranes as well as the surface structure. Peak fitting regimens determined whether the materials discovered were foulants deposited (as indicated by the N (Is) data) on the surface or materials that had become chemically bound to the surface. To be chemically bound to the surface, the foulant must show an oxidation state indicative of a bond with membrane substituents. If the foulant showed a chemical composition not associated with the membrane, it was determined to be lying on the surface (physisorbed) and not chemically attached. This was the case for calcium on LFCl (Ca (2pl, 2p3)BE 350.3-346.9 eV). However, this finding does not preclude the possibility of calcium complexation with functional groups of the RO membranes used... 

Samarskite-(Y) is a complex oxide of rare earths, uranium, calcium, niobium, tantalum and other elements it always occurs in the metamict state. This characteristic has been an obstruction to the study of the chemistry and crystal structure of this mineral. Although many chemical formulae and crystallographic data for samar-skite-(Y) have been proposed, no complete chemical or structural understanding of samarskite-(Y) has been achieved. 

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