Decomposition thermodynamics

Chemical Properties. Although hydrogen sulfide is thermodynamically stable, it can dissociate at very high temperatures. The decomposition thermodynamics and kinetics have been reviewed and the equihbrium constant for the reaction has been deterrnined (101,102) ... 

Favorskaya and Ponomaryeva92 measured the vapor pressure of T12S04 in the range 973 to 1233 K by a dynamic method, finding no evidence of decomposition. Thermodynamic calculations suggest the decomposition begins above 1200 K. Densities are given in Tables 4.130, transitions in Table 4.131, and thermodynamic data in Tables 4.132 to 4.135. 

We tend to say that substances are stable or unstable , reactive or unreactive but these terms are relative and may depend on many factors. Is important to specify the conditions of temperature and pressure, and what other substances are present or could act as potential routes to decomposition. Thermodynamic and kinetic factors can also be important. 

Models and cocks A sodium-concrete ablation model SCAM [5.25] has been developed by Sandia. Very simple models related to evrq)ourable and non-ev K>urable water release rates are to be found in [5.26]. More recently liie RESSORT and SORBET Codes [5.27] have been developed and tested. Modelling covers chemical decomposition, thermodynamic equilibrium, and mass transfer of water, air, H2 and CO2. Heat transfer remains very important and may be strongly influenced by bubbling at the interface. Further developments are necessary. 

Thus, consistent with the aforementioned analyses, the substitution of H by Ph in carbene carbon makes diazocarbene decomposition thermodynamically more feasible and irreversible. 

Cell Volta.ge a.ndIts Components. The minimum voltage required for electrolysis to begin for a given set of cell conditions, such as an operational temperature of 95°C, is the sum of the cathodic and anodic reversible potentials and is known as the thermodynamic decomposition voltage, is related to the standard free energy change, AG°C, for the overall chemical reaction,... 

Table 7. Thermodynamic Decomposition Voltage of Chlor—Alkali Cells at 25°C...

An excess of crotonaldehyde or aUphatic, ahcyhc, and aromatic hydrocarbons and their derivatives is used as a solvent to produce compounds of molecular weights of 1000—5000 (25—28). After removal of unreacted components and solvent, the adduct referred to as polyester is decomposed in acidic media or by pyrolysis (29—36). Proper operation of acidic decomposition can give high yields of pure /n j ,/n7 j -2,4-hexadienoic acid, whereas the pyrolysis gives a mixture of isomers that must be converted to the pure trans,trans form. The thermal decomposition is carried out in the presence of alkaU or amine catalysts. A simultaneous codistillation of the sorbic acid as it forms and the component used as the solvent can simplify the process scheme. The catalyst remains in the reaction batch. Suitable solvents and entraining agents include most inert Hquids that bod at 200—300°C, eg, aUphatic hydrocarbons. When the polyester is spHt thermally at 170—180°C and the sorbic acid is distilled direcdy with the solvent, production and purification can be combined in a single step. The solvent can be reused after removal of the sorbic acid (34). The isomeric mixture can be converted to the thermodynamically more stable trans,trans form in the presence of iodine, alkaU, or sulfuric or hydrochloric acid (37,38). 

Physical Properties. Thionyl chloride [7719-09-7], SOCI2, is a colorless fuming Hquid with a choking odor. Selected physical and thermodynamic properties are Hsted in Table 6. Thionyl chloride is miscible with many organic solvents including chlorinated hydrocarbons and aromatic hydrocarbons. It reacts quickly with water to form HCl and SO2. Thionyl chloride is stable at room temperature however, slight decomposition occurs just... 

The thermodynamic properties of gypsum decomposition, which involve two distinct steps,... 

This decomposition is thermodynamically favored by decreasing temperature and increasing pressure (28). Decomposition is extremely slow below 673 K in the absence of a catalyst however, between 673—873 K many surfaces, particularly iron (29), cobalt, and nickel (30), promote the disproportionation reaction. 

Dichlorine monoxide is the anhydride of hypochlorous acid the two nonpolar compounds are readily interconvertible in the gas or aqueous phases via the equilibrium CI2 O + H2 0 2H0Cl. Like other chlorine oxides, CI2O has an endothermic heat of formation and is thus thermodynamically unstable with respect to decomposition into chlorine and oxygen. Dichlorine monoxide typifies the chlorine oxides as a highly reactive and explosive compound with strong oxidhing properties. Nevertheless, it can be handled safely with proper precautions. 

When hydroxypteridines are considered, it must be borne in mind that these compounds exist principally in the pteridinone forms, containing thermodynamically stable amide functions, and consequently have low reactivity. Their stability towards acid and alkali correlates well with the number of electron-donating groups which apparently redress the deficit of ir-electrons located at the ring nitrogen atoms. Quantitative correlations can be seen in the decomposition studies of various pteridinones (Table 7). These results are consistent with the number of the oxy functions and their site at the pteridine nucleus. The... 

Most chemical reactions are exothermic. In the few endothermic reactions that are known, heat is absorbed into the reaction product or products, which are known as endothermic or energy-rich compounds. Such compounds are thermodynamically unstable because heat woiild be released on decomposition of their elements. The majority of endothermic compounds possess a tendency toward insta-bihty and possibly explosive decomposition under various circumstances of initiation. 

The iron-carbon solid alloy which results from the solidification of non blastfurnace metal is saturated with carbon at the metal-slag temperature of about 2000 K, which is subsequendy refined by the oxidation of carbon to produce steel containing less than 1 wt% carbon, die level depending on the application. The first solid phases to separate from liquid steel at the eutectic temperature, 1408 K, are the (f.c.c) y-phase Austenite together with cementite, Fe3C, which has an orthorhombic sttiicture, and not die dieniiodynamically stable carbon phase which is to be expected from die equilibrium diagram. Cementite is thermodynamically unstable with respect to decomposition to h on and carbon from room temperature up to 1130 K... 

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