Calcium carbonate CaCO decomposition

The decomposition in the soil is however influenced by varying conditions and by the presence of lime and other fertilizer salts so that its exact value is yet in question. Among the products obtained by its decomposition in the soil are ammonia NH3, calcium carbonate, CaCOs, cyan-amide, HgN—CN, di-cyan di-amide, (H2NCN)2 or H2N—(HN)C—NH(CN), cyano guanidine and urea OC(NH2)2). Further discusion of its use as a fertilizer is not desirable here. 

The weight lost by a sample heated to a given temperature helps the inorganic or analytical chemist to determine the composition of a compound and follow the reactions involved in its decomposition. It also enables the analytical chemist to identify crystals of unknown composition or determine the percentage of a given compound in a mixmre of compounds. For example, if pure calcium carbonate (CaCOs) is heated to 850°C, it loses 44% of its weight (Fig. 16.1). Also, the gas evolved can be collected and identified as CO2. This observation virtually confirms that the reaction... 

Quicklime (CaO) is produced by the thermal decomposition of calcium carbonate (CaCOs). Calculate the volume of CO2 produced at STP from the decomposition of 152 g of CaCOs according to the reaction... 

The concept of a reversible chemical reaction is illustrated by the decomposition of calcium carbonate, wliicli wlien heated forms calcium oxide and carbon dioxide gas. At equilibrium, tins system exerts a definite decomposition pressure of CO2 for a given temperature. When the pressure falls below tliis value, CaCOs decomposes. Assume tliat a cylinder is fitted with a frictionless piston and contains CaCOi, CaO, and CO2 in equilibrium. It is immersed in a constant-temperaturebath, as shown in Fig. 2.3, witli the temperature adjusted to a value such that the decompositionpressure is just sufficient to balance the weight on the piston. The system is in mechanical equilibrium, tire temperature of tire system is equal to that of the bath, and the chemical reaction is lield in balance by the pressure of the CO2. Any change of conditions, however slight, upsets tire equilibrium and causes the reaction to proceed in one direction or the other. 

Thermal decomposition. Calcium carbonate decomposes into calcium oxide and carbon dioxide when heated. The heat of dissociation of CaCOs is 1781 kJ/... 

The above-listed features of the formation of X-ray amorphous and crystalline products are observed in the decompositions of many other compounds. Haul and Schoning [41] applied an X-ray method (line-width technique) to study the structure of the decomposition products of dolomite as a function of temperature. The experiments were carried out both in vacuum and in a CO2 environment. In vacuum, decomposition proceeded to the CaO and MgO oxides, and in a CO2 environment, to CaCOs and MgO. This difference is reasonable. It originates from the calcium carbonate being more stable than the magnesium carbonate (the enthalpies of formation of CaCOs and MgCOg at 800 K are —1,154 and —1,045 kJ mol respectively). The size of the crystallites formed in vacuum [41] increased monotonically from 6nm for MgO and 13 nm for CaO to 120-140 nm with the temperature increasing within the range 700-1,000° C. (Oversaturation decreases in these conditions from 10 to 10 for MgO, and from 10 to 10 for CaO.)... 

The thermal stability of calcium carbonate (CaC03) nanoparticles on polybutadiene rubber (PBR) were studied by Shimpi and Mishra [105]. They observed that the incorporation of nano CaCOs in PBR shows better thermal stability. At 12 wt% of nano CaCOs (21, 15, and 9 nm) filled in PBR shows decomposition temperature at 491, 483, and 472 °C, respectively. At 4 wt% loading of filler, decomposition temperature is observed to be 488,480,450 °C for nano CaCOs (21, 15, and 9 nm), respectively. This enhancement in thermal stability is due to uniform dispersion of nano CaCOs throughout the matrix that keeps the rubber chains intact on cross-linking, which prevent out diffusion of the volatile decomposition product [106]. The presence of nanoinorganic particles in between the mbber chains is responsible for preventing the diffusion of the volatile decomposition products firom the mbber nanocomposites at same time. It is clear that nanoinorganic filler provides better thermal stability as compared with commercial micron size filler. 

When heated, both barium carbonate (BaC03) and calcium carbonate (CaC03) release carbon dioxide (CO2), leaving barium oxide (BaO) and calcium oxide (CaO), respectively. In an experiment, a mixture of BaCOs and CaCOs with a combined mass of 63.67 g produces 19.67 g of CO2. Calculate the mole and mass fractions of barium carbonate and calcium carbonate in the original mixture, assuming complete decomposition of the compounds. 

Calcium carbonate, CaC03(s), decomposes upon heating to give CaO(s) and COzfg). A sample of CaCOs is decomposed, and the carbon dioxide is collected in a 250-mL flask. After the decomposition is complete, the gas has a pressure of 1.3 atm at a temperature of 31 °C. How many moles of CO2 gas were generated ... 

Observe that AS° for the decomposition of calcium carbonate is a positive quantity. This is reasonable because the gas formed, CO2, has a much higher molar entropy than either of the solids, CaO or CaCOs. As a matter of fact, a reaction that results in an increase in the number of moles of gas is almost always accompanied by an increase in entropy. Conversely, if the number of moles of gas decreases, AS° is a negative quantity. Consider, for example, the reaction... 

Drying a.nd Calcination. The simplest pyrometaHurgical operation is the evaporation of free water and the decomposition of hydrates and carbonates. A typical reaction is the decomposition of pure limestone [1317-65-3] CaCO, to calcium oxide [1305-78-8] and carbon dioxide ... 

By the double decomposition of calcium nitrate and ammonium carbonate (or sulfate) in solution Ca(NO,), + (NH4),CO, - CaCO, + 2NH4NO,... 

---