Heat of formation table

Table 55. Estimated heats of formation Table 56. The carbon-carbon double bond...

AIF3 is made by reaction of AI2O3 with HF gas at 700 °C (equation 17), while the rest of the trihalides may be prepared by the direct combination of the elements, a highly exothermic process. Of the four aluminum trihalides, AIF3 is unique in being nonvolatile, insoluble, and in possessing a much higher heat of formation (Table 5). 

Use tabulated heats of formation (Table B.l) to determine the standard heats of the foUow ing reactions in kJ/mol, letting the stoichiometric coefficient of the first reactant in each reaction equal... 

Proceeding as before, data for the alkynes were fitted (A. Y. Meyer, unpublished results) using parameters for structure and heat of formation (Table 8) based on experimental information which is even more limited than in the case of alkenes. 

In more recent work we have extended those calculations to the same 58 compounds used as the standard for MM4 heats of formation (Table 11.1), so that we can make comparisons of the results obtained by these and other methods. Since the original quantum mechanical work was published, computer capabilities have improved to where it has become possible to carry out MP2 and MP4 calculations on this same group of compounds. The optimized parameter set, together with the overall accuracy of the results, is shown for each of several methods in Table 11.6. There is... 

The heats of formation of large number of compounds are tabulated at standard conditions (heat of formation tables available in Perry s Chemical Engineer s Handbook, 1997). The standard conditions are usually defined at 25°C and 1 atm and the phase that is normal for compounds under these conditions (carbon is solid, H2O is liquid, CO2 is gas, etc.). 

Reaction (3) as it proceeds toward CO production is endothermic, with a heat of reaction equal to 9.84 kcal/g-moL In all the preceding cases, heats of reaction may be easily calculated at any temperature from heats of formation tables, where... 

For pure organic materials, it is also possible to calculate the heating value starting from the heats of formation found in tables of thermodynamic data. The NHV is obtained using the general relation of thermochemistry applicable to standard conditions of pressure and temperature (1 bar and 25°C)) f 9j... 

Table 7-2 also contains, besides the values for heats of formation, values for... 

Another scheme for estimating thermocheraical data, introduced by Allen [12], accumulated the deviations from simple bond additivity in the carbon skeleton. To achieve this, he introduced, over and beyond a contribution from a C-C and a C-H bond, a contribution G(CCC) every time a consecutive arrangement of three carbon atoms was met, and a contribution D(CCC) whenever three carbon atoms were bonded to a central carbon atom. Table 7-3 shows the substructures, the symbols, and the contributions to the heats of formation and to the heats of atomization. 

Table 7.3. The Allen scheme substructures, notations, and contributions to heats of formation and heats of atomization (values in kj/mol).

The heats of formation of most organic com pounds are derived from heats of reaction by arith metic manipulations similar to that shown Chemists find a table of AH values to be convenient because it replaces many separate tables of AH° values for indi vidual reaction types and permits AH° to be calcu lated for any reaction real or imaginary for which the heats of formation of reactants and products are available It is more appropriate for our purposes however to connect thermochemical data to chemi cal processes as directly as possible and therefore we will cite heats of particular reactions such as heats of combustion and heats of hydrogenation rather than heats of formation... 

You have seen that measurements of heats of reaction such as heats of combustion can pro vide quantitative information concerning the relative stability of constitutional isomers (Section 2 18) and stereoisomers (Section 3 11) The box in Section 2 18 described how heats of reaction can be manipulated arithmetically to generate heats of formation (AH ) for many molecules The following material shows how two different sources of thermo chemical information heats of formation and bond dissociation energies (see Table 4 3) can reveal whether a particular reaction is exothermic or en dothermic and by how much... 

The following data (Table 1) for molecules, including hydrocarbons, strained ring systems, molecules with heteroatoms, radicals, and ions comes from a review by Stewart.For most organic molecules, AMI reports heats of formation accurate to within a few kilocalories per mol. For some molecules (particularly inorganic compounds with several halogens, such asperchloryl fluoride, even the best semi-empirical method fails completely. 

Table 8—1. Heats of formation of selected m olecules from AMI calculations...

The tnhahdes of phosphoms usually are obtained by direct halogenation under controlled conditions, eg, in carbon disulfide solution in the case of the triiodide. Phosphoms trifluoride [7647-19-0] is best made by transhalogenation of PCl using AsF or Cap2. AH of the phosphoms tnhahdes are both Lewis bases and acids. The phosphoms tnhahdes rapidly hydroly2e in water and are volatile. Examination by electron diffraction has confirmed pyramidal stmctures for the gaseous tnhahde molecules (36). Physical properties and heat of formation of some phosphoms hahdes are hsted in Table 7. 

Physical Properties. Sulfur dioxide [7446-09-5] SO2, is a colorless gas with a characteristic pungent, choking odor. Its physical and thermodynamic properties ate Hsted in Table 8. Heat capacity, vapor pressure, heat of vaporization, density, surface tension, viscosity, thermal conductivity, heat of formation, and free energy of formation as functions of temperature ate available (213), as is a detailed discussion of the sulfur dioxide—water system (215). 

A composite curve of heat of infinite dilution of oleum from reported data (3,88—90) is presented in a compiled form in the Hterature (91), where heats of formation of oleums from Hquid or gaseous SO are also reported (Tables 5 and 6). Heat of vaporization data are also available (92). Oleum heat capacity data are presented in Figure 18 (76) solubiUty data for SO2 in oleum can be found in Reference 69. 

Table 5. Heat of Formation of Oleums from Liquid SO, ...

Data relating to changes of state of selected titanium compounds are Hsted in Table 1. Heats of formation, free energy of formation, and entropy of a number of titanium compounds at 298 and 1300 K are collected in Table 2. 

Combustion. The primary reaction carried out in the gas turbine combustion chamber is oxidation of a fuel to release its heat content at constant pressure. Atomized fuel mixed with enough air to form a close-to-stoichiometric mixture is continuously fed into a primary zone. There its heat of formation is released at flame temperatures deterruined by the pressure. The heat content of the fuel is therefore a primary measure of the attainable efficiency of the overall system in terms of fuel consumed per unit of work output. Table 6 fists the net heat content of a number of typical gas turbine fuels. Net rather than gross heat content is a more significant measure because heat of vaporization of the water formed in combustion cannot be recovered in aircraft exhaust. The most desirable gas turbine fuels for use in aircraft, after hydrogen, are hydrocarbons. Fuels that are liquid at normal atmospheric pressure and temperature are the most practical and widely used aircraft fuels kerosene, with a distillation range from 150 to 300 °C, is the best compromise to combine maximum mass —heat content with other desirable properties. For ground turbines, a wide variety of gaseous and heavy fuels are acceptable. 

Table 11.1 Standard heats of formation of some metal silicates at room temperature (from metal oxides)...

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