Dissociation energy specific heat

McMillan and Golden employ the commonly invoked uncertainty of 5 kJ/mol (lkcal/mol) for dissociation energies and most of the uncertainties for the heats of formation fall in the same range. The reader is urged to refer to the McMillan and Golden reference for the specific uncertainty values. 

As discussed previously, in many propulsion systems the recovery of a large fraction of the dissociation energy in the nozzle expansion through recombination is difficult to achieve. While the assumption of frozen flow with respect to recombination reactions appears necessary for many heat transfer rocket nozzle expansions, it is possible that condensation phenomena are sufficiently rapid to provide near equilibrium flow with respect to phase changes. For this special possibility, phase equilibrium in the presence of frozen dissociation, it has been shown theoretically (48) that the performance in terms of specific impulse of propellants containing light metallic elements can exceed the performance of hydrogen. 

With diatomic molecules, energies of dissociation may be determined in various other ways. One method depends upon the variation with temperature of the equilibrium constant of the dissociation, and application of the thermodynamic relation din JT/dT = AUjBT, A second method involves determinations, based upon measurements of explosion temperatures, of the apparent specific heat of the partially dissociated gas. 

The CHF and TRP values can be increased by modifying the pertinent parameters such as the chemical bond dissociation energy and thermal diffusion (combination of the density, specific heat and thermal conductivity). 

The catalytic properties of the PGM in the heterogeneous catalysis are based on the moderate values of the heats of adsorption which correspond to the dissociation energies of the reactant molecules. Figure 3.1-251 [1.276] and Table 3.1-188 [1.218] give some values of the heat of adsorption and binding energies between adsorbates and surface atoms on various noble metal single crystals. The heat of adsorption increases for different orientations of the crystal surface planes of the fee crystals in the order [111] < [100] < [110] (Table 3.1-189 [1.218]). The catalytic activities are element-specific for different re-... 

Information concerning unimolecular potential energy surfaces can be acquired from several sources. Thermochemical measurements provide bond dissociation energies Dq and heats of reaction AHq. Analyses of the vibrational spectra of a unimolecular reaction s reactants and products yields their quadratic force constants, and if the data is sufficiently complete, also, their cubic and quartic force constants. From kinetic measurements of the unimolecular rate constant at high pressure the phenomenological Arrhenius A factor Aee and activation energy can be derived. If one can show that that the activated complex theory is valid for a specific unimolecular reaction its threshold energy Eq and the entropy difference between the activated complex and molecule can be found from... 

The alkali promotion of CO dissociation is substrate-specific, in the sense that it has been observed only for a restricted number of substrates where CO does not dissociate on the clean surface, specifically on Na, K, Cs/Ni( 100),38,47,48 Na/Rh49 and K, Na/Al(100).43 This implies that the reactivity of the clean metal surface for CO dissociation plays a dominant role. The alkali induced increase in the heat of CO adsorption (not higher than 60 kJ/mol)50 and the decrease in the activation energy for dissociation of the molecular state (on the order of 30 kJ/mol)51 are usually not sufficient to induce dissociative adsorption of CO on surfaces which strongly favor molecular adsorption (e. g. Pd or Pt). 

While it sublimes below 250° at press 0 to 150 mm Hg, it shows slow decompn between 250-450° at 70 mm and betw 250°-310° at 150 mm. Amm azide is one of the more stable azides (Ref 20). According to Gray Wad-dington it vaporizes and dissociates into NH3 HNa and then the HN3 explodes. A hot wire causes Amm azide to burn quietly in air rather than detonate (Ref 20). This azide detonates violently when properly initiated, heared rapidly or heated under confinement (Refs 2 10). Temp of expln is 1400° and specific energy 7102 kg/1 (Ref 9). It is considered a non-brisant expl as it decomposes in an ideal manner producing only innocuous gases (1148 1/kg at 0° and 760 mm) (Ref 6). The toxicity of Amm azide is unknown (Ref 22). Ephraim (Ref 19) states that this salt may be regarded as a polymer of imide(NH). ... 

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