Calcium oxide formation

Hydrides. Zirconium hydride [7704-99-6] in powder form was produced by the reduction of zirconium oxide with calcium hydride in a bomb reactor. However, the workup was hazardous and many fires and explosions occurred when the calcium oxide was dissolved with hydrochloric acid to recover the hydride powder. With the ready availabiHty of zirconium metal via the KroU process, zirconium hydride can be obtained by exothermic absorption of hydrogen by pure zirconium, usually highly porous sponge. The heat of formation is 167.4 J / mol (40 kcal/mol) hydrogen absorbed. 

Calcium Oxide (lime, Quicklime, Burnt Lime, Calx, Unslaked Lime, Fluxing Lime). CaO, mw 56.08, white or greyish-white lumps or powd, mp 2580°, bp 2850°, d 3.25-3.40g/cc. SI sol in w with formation of calcium hydroxide and evolution of large amts of heat sol in acids, and insol in ethanol. Coml prepn consists of heating calcium carbonate in kilns at 1000—1100° until all of the C02 is driven off. Lab prepn is by burning calcium carbonate or calcium oxalate at about 800° using a quartz crucible in an electric furnace... 

Removing a product from a system at equilibrium also makes Q < and leads to the formation of additional products. This behavior is commonly used to advantage in chemical synthesis. For example, calcium oxide (lime), an important material in the construction industry, is made by heating calcium carbonate in a furnace to about 1100 K CaCOs ( ) CaO (s) + CO2 (g) = (pco2 = 10 at 1100 K... 

As we have already shown, the presence of cations in orthophosphoric acid solution can have a decisive effect on cement formation. As noted above, Kingery (1950b) found it necessary to modify orthophosphoric add, by the addition of calcium, to obtain cement formation with calcium oxide. Also, Finch and Sharp (1989) had to modify orthophosphoric add, with either ammonium or aluminium, to achieve cement formation with magnesium oxide. 

Calcinating limestone (composed of calcium carbonate) removes its volatile component (carbon dioxide) and results in the formation of quicklime (composed of calcium oxide) (see Textbox 33). 

In the gasifier, coal is fed along with calcium oxide, steam, and oxygen. The excess steam in the gasifier drives the following reaction toward the formation of H2 ... 

Q O The standard molar enthalpy of formation of calcium carbonate is -1207.6 kj/mol. Calculate the enthalpy of formation of calcium oxide, given the following equation. 

Currently, thermal reduction processes have replaced the electrolysis method. The starting material in these methods is limestone, which is calcined to produce calcium oxide. The latter is ground, mixed and compacted with aluminum, and reduced at temperatures between 1,000° to 1,200°C under vacuum. Calcium vapors formed in low yield under such thermodynamic conditions are transferred from the reactor and condensed in cool zones, thus shifting the equilibrium to allow formation of more calcium vapors. The reactions are as follows ... 

Unlike calcium oxide, at ordinary temperatures magnesium oxide is stable in water. There is very little formation of magnesium hydroxide. The reaction, however, is rapid at elevated temperatures. The acids form their magnesium salts which, if water-soluble, may be obtained by evaporation of the solution ... 

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... 

The lattice energy of calcium oxide (Born-Lande) is 3554 kJ mol the enthalpy of lattice formation is -3554 - 6 = -3560 kJ mol1. The calculated standard enthalpy of formation of calcium oxide is -677 kJ mol about 7% more exothermic than the observed value, probably due to the inherent error in the calculation. 

In 1861, W. Gossage showed that calcium sulphide is insoluble in water, and is but little attacked by sodium carbonate he also showed that the residue left after the lixiviation of black ash is a mixture of calcium monosulphide and carbonate, even when no sodium sulphide is present in the liquor and that if any sodium sulphide be present in the liquor, it is derived from the formation of calcium polysulphides in the black ash which can be prevented by using an excess of limestone. Both J. W. Kynaston and W. Gossage showed that no sodium hydroxide is present in black ash because (a) sodium hydroxide melted with black ash forms calcium oxide and sodium carbonate and (b) no sodium hydroxide can be extracted with... 

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