Calcium carbonate, decomposition, heat

Reacting species, predominant, 80 Reaction coordinate, 133 Reaction heat, 135 additivity of, 111 measurement of, 111 Reaction rates, 124 factors affecting, 125 Reactions, 38,129 acid-base, 188 balancing, 42, 217, 219 calcium carbonate decomposition, 143... 

Debray, in 1867, carried out the first measurements of the dissociation pressure of calcium carbonate. He heated Iceland Spar in a tube to the temperature of boiling mercury, sulphur, cadmium and zinc (357, 445, 767, 907 °C respectively). He found no decomposition at the first two, but measurable pressures at the boiling points of cadmium and zinc. The first exact measurements of the dissociation pressure were made by Le Chatelier in 1886. 

Problem 8.19. Calcium carbonate is heated in a crucible open to the atmosphere. The reaction is a decomposition and the equation for the reaction is CaCOjfs) CaO(s) + C02(g). Is the reaction reversible as performed ... 

As it is known, that the heat consiunption of the clinkering process is mainly due to the calcium carbonate decomposition and the long period (about 20 min) of clinker heating in sintering zone at maximirm temperamre, to assirre full alite formation. Therefore the energy consirmption increases with lime saturation factor (see Chap. 2). 

Carbon dioxide and calcium carbonate The effect of carbon dioxide is closely linked with the bicarbonate content. Normal carbonates are rarely found in natural waters but sodium bicarbonate is found in some underground supplies. Calcium bicarbonate is the most important, but magnesium bicarbonate may be present in smaller quantities in general, it may be regarded as having properties similar to those of the calcium compound except that on decomposition by heat it deposits magnesium hydroxide whereas calcium bicarbonate precipitates the carbonate. 

Calcium oxide can be produced from extensive heating of limestone. Primarily composed of calcium carbonate, limestone is extracted from both underground and surface mines and heated to temperatures exceeding 180°F to convert the calcium carbonate into calcium oxide. This thermal decomposition reaction also generates carbon dioxide gas. 

Fig. 60. TMBA- and MS-curves of the decomposition of calcium carbonate. Heating rate...

About 1865, E. Kopp, and P. W. Hofmann tried to revive the oxysulphide theory, but J. Pelouze refuted their arguments and after a long study of the reactions, J. Kolb confirmed A. Scheurer-Kestner s work, but concluded that in the main reaction the calcium carbonate loses its carbon dioxide by the action of the carbon dioxide in the fire gases. A. Scheurer-Kestner then showed that in this last conclusion J. Kolb is in error, because black ash can be made in crucibles without any assistance from the fire gases that the decomposition of the calcium carbonate, even in the presence of coal, requires a higher temp, than the reduction of the sodium sulphide and that black asb is obtained by directly heating sodium sulphide with calcium carbonate. 

The story of steel begins when iron ore is fed into a blast furnace (Fig. 16.45). The furnace, which is approximately 40 m in height, is continuously filled at the top with a mixture of ore, coke (impure carbon obtained by heating coal in the absence of air), and limestone. Each kilogram of iron produced requires about 1.75 kg of ore, 0.75 kg of coke, and 0.25 kg of limestone. The limestone, which is primarily calcium carbonate, undergoes thermal decomposition to calcium oxide (lime) and carbon dioxide. The calcium oxide, which contains the Lewis base 02, helps to remove the acidic (nonmetal oxide) and amphoteric impurities from the ore ... 

Under ordinary soil conditions all tlie above stages are realised, but by heating with water under pressure, complete decomposition into calcium carbonate and ammonia takes place. 

Wear face shield, goggles, laboratory coat, and nitrile rubber gloves. Cover spill with a 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand. Using a plastic shovel, scoop into a pail of water in the fume hood (about 66 mL/g). Cautiously add aqueous 5.5% ceric ammonium nitrate (4 volumes per volume of aqueous solution) and stir for an hour. If the solution remains orange, an excess of ceric ammonium nitrate is present and the azide has been completely destroyed. The solution can be washed into the drain with at least 50 times its volume of water.6,7 The solid residue is treated as normal refuse. A spot test for checking if azide is completely destroyed is as follows Place a drop of the test solution in the depression of a spot plate and treat with 1 or 2 drops of dilute hydrochloric acid. Add a drop of ferric chloride solution and gently heat the spot plate. A red color indicates hydrazoic acid and incomplete decomposition. 

The concept of a reversible chemical reaction may be illustrated by the decomposition of calcium carbonate, which when heated forms calcium oxide and carbon dioxide gas. At equilibrium, this system exerts a definite decomposition pressure of C02 for a given temperature. When the pressure falls below this value, CaCOj decomposes. Assume now that a cylinder is fitted with a frictionless piston and contains CaC03, CaO, and C02 in equilibrium. It is immersed in a constant-temperature bath, as shown in Fig. 2.5, with the temperature adjusted to a value such that the decomposition pressure is just sufficient to balance the weight on the piston. The system is in mechanical equilibrium, the temperature of the system is equal to that of the bath, and the chemical reaction is held in balance by the pressure of the COj. Any change of conditions, however slight,... 

Calcium carbonate decomposes into calcium oxide and carbon dioxide when it is heated. Based on this information, predict the products of the following decomposition reactions. 

Mutation data reported. Reacts with moisture to form sulfuric acid. Mixtures with calcium hypochlorite + starch + sodium carbonate explode when compressed. Violent reaction with acetic anhydride + ethanol may lead to ignition and a vapor explosion. Incompatible with calcium hypochlorite. When heated to decomposition it emits toxic fumes of SO and Na20. See also SULFATES. 

Ketones from Acids.— Another important reaction of acids is the formation of ketones and aldehydes by the decomposition of salts of the acids. When calcium acetate is heated the calcium remains combined with part of the two carboxyl groups as calcium carbonate and the two alkyl radicals become united by the remaining carbonyl group forming a ketone. 

If the reaction is carried out in a closed vessel, the conversion is not complete, as the partial pressures of the gases formed would attain very large values if any considerable quantity of water vapour, the gases are removed as fast as they are formed, so that their partial pressure at the surface of the carbon is maintained at a small value. In this way only is the complete oonversion of the carbon into water gas possible. Currents of gases are employed in a similar manner in the decomposition of calcium carbonate (the burning of lime) and in the reduction of ores by carbon monoxide. This procedure is used extensively in technical processes. 

Calcium oxide has the ancient name of quicklime. Most carbonates, when heated, undergo thermal decomposition to form the metal oxide and carbon dioxide. Sodium and potassium carbonate, on the other hand, don t decompose at all when heated, because sodium and potassium are very reactive metals, so their compounds are very stable. 

The decomposition of calcium carbonate to calcium oxide and carbon dioxide needs a lot of heat energy. 

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