Thermochemistry transferring

Ferrosihcon production is a nearly slag-free process. Most of the impurities introduced into the furnace via the raw materials and any other sources are transferred to the product. In order to produce high purity grades of ferrosihcon, the tapped ahoy is refined by treating with gas mixtures and slag additions. The principle of ferrosihcon refining is quite similar to that of sihcon. Details on the thermochemistry of ferrosihcon refining and practical examples are available (24). 

The first systematic measurements of the reactions of ions with molecules in the gas phase were initiated largely by workers associated with analytical mass spectrometry.4-6 It was the rapidly expanding area of ion-molecule reactions which led to the origin of Gas-Phase Ion Chemistry as a distinct field.7 The discovery that ion-molecule equilibria in the gas phase can be determined by mass spectrometric techniques8 led to an explosion of thermochemical measurements based on determination of equilibria by a variety of techniques.9 Significantly, for the first time, information could be obtained on the thermochemistry of reactions which had solution counterparts of paramount importance such as acidities and basicities. These were obtained from proton transfer equilibria such as,... 

Thermochemistry is the branch of thermodynamics concerned with the way energy is transferred, released or consumed during a chemical reaction. 

Background Thermochemistry is the study of heat changes and transfers associated with chemical reactions. In this thermochemical laboratory study, you will determine the enthalpy change that occurs when a strong base, sodium hydroxide, reacts with a strong acid, hydrochloric acid. Other mixtures studied will include ammonium chloride mixed with sodium hydroxide and ammonia mixed with hydrochloric acid. These three reactions are represented as ... 

Use of medium-scale heat flow calorimeter for separate measurement of reaction heat removed via reaction vessel walls and via reflux condenser system, under fully realistic processing conditions, with data processing of the results is reported [2], More details are given elsewhere [3], A new computer controlled reaction calorimeter is described which has been developed for the laboratory study of all process aspects on 0.5-2 1 scale. It provides precise data on reaction kinetics, thermochemistry, and heat transfer. Its features are exemplified by a study of the (exothermic) nitration of benzaldehyde [4], A more recent review of reaction safety calorimetry gives some comment on possibly deceptive results. [5],... 

The study of energy and energy transfer is known as thermodynamics. Chemists are interested in the branch of thermodynamics known as thermochemistry the study of energy involved in chemical reactions. 

Bouchoux, G. Salpin, J.Y. Leblanc, D. A Relationship Between the Kinetics and Thermochemistry of Proton Transfer Re-... 

The reaction between OH and phenol lends itself to an analysis of its thermochemistry. On the basis of E7( OH) = 2.3V/NHE and E7(PhO ) = 0.97 V/NHE [42], the formation of PhO and H2O via an electron-transfer mechanism is exothermic byl.33V = 31 kcal mor In spite of this, the reaction proceeds by addition, as outlined in Eq. 24. Again, the propensity of OH to add rather than to oxidize can be understood in terms of the transition state for addition being stabilized by contributions from bond making, in contrast to electron transfer which requires pronounced bond and solvent reorganization which results in a large (entropy-caused) free energy change. 

The thermochemistry of sulfur radicals in the gas phase has been reviewed. Methylsulfonyl radicals and cations have been produced by femtosecond collisional electron transfer in the gas phase. When formed by vertical collisional electron transfer from cation CH3SO2+, radical CH3S02 dissociates to CH3 and SO2. Radical CH30S0 exists as a mixture of syn (19a) and anti (19b) isomers which are stable when formed by collisional electron transfer to the corresponding cation. Dissociation of both isomers of CH30S0 formed CH3 and SO2 via isomerization to methylsulfonyl radical. An ab initio study on the formation of the thiyl peroxyl radical has also been reported. Julolidylthiyl radicals (20) were formed by femtosecond photo-dissociation of the corresponding disulfide and have been observed... 

The CBS-QB3 potential energy surface accounts for the various experimentally observed products, including hydroperoxyl radical, propene, HO, propanal, and oxirane (c-CsHgO). The activation barrier for simultaneous 1,4-H transfer and HO2 expulsion, obtained via calculations, compares well to the experimentally observed barrier (26.0kcal/mol) of DeSain et al. This work provides some ramifications for larger alkylperoxy radicals multiple conformers of long alkylperoxy radicals are likely to play a role in the overall oxidation chemistry and dictate consideration for correct treatment of thermochemistry at lower temperatures T< 500 K), unimolecular reactions dictate peroxy radical chemistry. 

A number of studies of H-atom transfer from hydrogen halides to free radicals, R + HX - RH + X, have been done by FPTRMS in which R was detected by photoionization, and its decay was monitored as a function of [HX] under pseudo-first-order conditions. When the rate coefficient is combined with determinations of the rate coefficient of the reverse reaction to obtain the equilibrium constant, the enthalpy of formation of the radical can be deduced. If the kinetics are accurately measured in isolation, this is a direct kinetic method which can be used to confirm (or otherwise) thermodynamic data obtained by classical, indirect kinetic methods which depend on correct mechanistic interpretation. In a number of instances free radical enthalpies of formation by these two different approaches have not been in good agreement. It is not the purpose of this short survey to discuss the differences, but rather to briefly indicate the extent to which the FPTRMS method has contributed to the kinetics of these reactions and to free radical thermochemistry. 

It was suggested earlier in this section that oxoacid salts such as CaC03 could be viewed as products of reactions between basic oxides (containing O2- discrete ions) and covalent (molecular/polymeric) oxides in which oxide ions are transferred to form oxo-anions. Analysis of the thermochemistry of such reactions has led to the formulation of a numerical scale of acidity for oxides. In Table 9.1 the acidity parameter a is listed for the most important binary oxides. Highly-negative values indicate a basic oxide, while acidic oxides have positive values. 

Recently, there has been considerable interest in determining thermochemical properties, such as the AH°( and EA values of carbenes, notably the halo- and dihalomethylenes, and both experimental and computational methods were applied to this end. One thorough ICR investigation produced heats of formation for CF2, CC12, CC1F, CFH and CC1H, from estimates of the thermochemistry of the proton transfer reaction of equation 44 where X and Y are F and/or Cl, and B is a base of known gas-phase basicity323. 

Table V presents a list of estimated enthalpies and half lives for molecular H-atom transfer (disproportionation) from tetralin to a number of unsaturated molecules. At 450°C, and even at 400°C, many structures will undergo rapid molecular disproportionation with tetralin. Approximate relative rates at 400°C for H-atom donation by molecular disproportionation for selected hydrogen donors are estimated below (sources for thermochemistry are given in footnote 1 of Table IV) ...

The thermochemistry of this system, discussed intermittently in what has come before, can be summarized here. Disproportionation is less favorable thermodynamically than recombination the equilibrium constant is 10 as compared to 10. Nonetheless, disproportionation can be made to be the more important reaction, even the nearly exclusive one, by virtue of the control exercised by the concentration of TMPD. The products of disproportionation, Mo and Mo-AN", do not react readily. The disproportionation products are "trapped" as such. In other words, the metal radicals are captured into an electron transfer cycle which prevents their falling to the most stable products, the dimer. The energetics of this system are depicted in Figtue 3. 

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