Crystals/crystallization calcium oxide

According to data [10,11], practically monophase anorthite can be synthesized after mechanical treatment of a mixture of calcium oxide with aluminium hydroxide and hydrated silica followed by thermal treatment at 1000°C for 4 h. Fig. 7.3 shows X-ray pattern of this mixture. After activation for 5 min (Fig. 7.3, curve 1), the reaction mixture exhibits a small amount of individual crystal calcium oxide (0.240 nm) and aluminium hydroxide (0.482, 0.436, 0.245 nm), while the major part of CaO is bound into an X-ray amorphous product. The annealing of the activated mixture at 1000°C gives anorthite (Fig. 7.3, curve 3) while the thermal treatment of non-activated mixture brings to the formation of intermediate product, wollastonite (Fig. 7.3, curve 2). The lines of this product are absent in X-ray patterns of the activated mixture. 

Ethyl chloride can be dehydrochlorinated to ethylene using alcohoHc potash. Condensation of alcohol with ethyl chloride in this reaction also produces some diethyl ether. Heating to 625°C and subsequent contact with calcium oxide and water at 400—450°C gives ethyl alcohol as the chief product of decomposition. Ethyl chloride yields butane, ethylene, water, and a soHd of unknown composition when heated with metallic magnesium for about six hours in a sealed tube. Ethyl chloride forms regular crystals of a hydrate with water at 0°C (5). Dry ethyl chloride can be used in contact with most common metals in the absence of air up to 200°C. Its oxidation and hydrolysis are slow at ordinary temperatures. Ethyl chloride yields ethyl alcohol, acetaldehyde, and some ethylene in the presence of steam with various catalysts, eg, titanium dioxide and barium chloride. 

FIGURE 14.21 An electron micrograph of the surface of cement, showing the growth of tiny interlocking crystals as carbon dioxide reacts with calcium oxide and silica. 

Figure 5.18.1 The NaCl crystal structure consisting of two interpenetrating face-centered cubic lattices. The face-centered cubic arrangement of sodium cations (the smaller spheres) is readily apparent with the larger spheres (representing chloride anions) filling what are known as the octahedral holes of the lattice. Calcium oxide also crystallizes in the sodium chloride structure.

Calcium chloride is obtained as a by-product in the manufacture of sodium carbonate (soda ash) by ammonia-soda (Solvay) process. The process involves the reaction of sodium chloride with calcium carbonate and ammonia. Calcium chloride is currently produced in bulk amounts by evaporation of natural underground brines. In the laboratory, calcium chloride can be prepared by treating bmestone with hydrochloric acid followed by evaporation of solution to obtain crystals. The crystals are dehydrated to obtain anhydrous salt. Calcium oxide or hydroxide may be used instead of carbonate. 

Calcium oxide crystallizes with a face-centred cubic lattice, a=481 pm and a density /)=3.35x10 kg m calculate a value for Z (Atomic masses of Ca and 0 are 40.08 and 15.999, respectively.)... 

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... 

Practical advantage of the method is that it does not require dry solvents. The resolving agent can be prepared by simple solution of DBTA monohydrate and half an equivalent amount of calcium oxide in hot 95 % ethyl alcohol. Crystallization of the diastereoisomeric coordination complex can be achieved by cooling and addition of cosolvents (e.g. acetone, toluene, ethyl acetate, etc.) or change ethyl alcohol to an ester type solvent. The enantiomers can be liberated from the crystalline complex by simple acidic workup procedure. [23]... 

Anhy2drous calcium sulfoaluminate is formed by calcination of lime, gypsum and bauxite. The active expansive ingredient, C A S is formed by solid-state reaction from mixtures of compounds composed of calcium oxide, aluminum oxide, sulfur trioxide gas formed during the calcination of gypsum, and bauxite. Crystal growth of CSAs is encouraged to proceed at a slow rate to preserve the potential force of expansion for extended periods [76],... 

This production of a peculiar degree of instability in the silver bromide, close to the atoms of sulphur in the sulphide, seems closely analogous to the other cases of promoter action, and the effects of a one-dimensional interface in a solid surface, which were considered in 3. It may be an effect of the same nature as the increased ease of decomposition of the calcium carbonate group, when this has calcium oxide groups adjacent to it. There is some evidence that the silver sulphide crystal lattice is rather more easily disorientated than the silver bromide, but since silver sulphide is, alone, not particularly sensitive to light, it seems certain that the sensitizing action of the sulphide speck must be due to a boundary action between the sulphide and the bromide.8... 

This can be dried with Linde-type sieves 4A or 13X, by prolonged contact and by passage through a column of the material, then distilled under reduced pressure. Other drying agents include calcium hydride, calcium oxide, barium oxide and calcium sulphate. It can also be fractionally crystallized by partial freezing. 

Calcium ferrite, Ca(Fe02)2, is formed as deep red or nearly black crystals 2 by heating together ferric oxide and calcium oxide. 

Potassium fluoride and calcium oxide have the same crystal structure. Which one should melt at the higher temperature Explain why. 

Lactose (1 kg.) in 9 liters of water is treated with 200 g. of calcium oxide (slaked and cooled), and the resulting mixture is maintained in a stoppered flask at room temperature, with frequent shaking, for 3 days. The solution is then heated in a boiling-water bath for 10 hours, filtered, and evaporated to a volume of 3 liters. The highly insoluble calcium a -D-isosaccharinate (199 g.) crystallizes it is accompanied by a small amount (14 g.) of calcium carbonate. The salt is separated by filtration and... 

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