Dissociation of gases

Today our knowledge of the specific heat and dissociation of gases at high temperatures has made extraordinary progress, primarily through the work of American scientists. However, even now, in order to solve a number of problems in high-temperature chemistry, analysis is needed of experimental data on phenomena of combustion, explosion and detonation. 

The application of this result to the measurement of the degree of dissociation of gases at high temperatures was suggested by Weide and Bichowsky 9 xhe method is to allow a small constant flow of gas at a constant low pressure to escape through a small hole. If the gas dissociates near the hole according to the equation A2 2A the various molecular species will escape at a rate which... 

The heat transfer phenomena and, in particular, the thermal boundary layer, are well understood for a cool, solid body immei l in a laminar hot gas stream in which no chemical reactions occur. The heat transfer can be predicted by the Nusselt number Nu = fi(Re, Pr). With some modifications, similar relationships hold for dissociation of gases, provided that Le, which describes the diffusion of the species, is close to unity... 

A plot of log I versus t yields D directly. In this case the emf versus concentration data are not needed. A major advantage of this method is that the slow step involving the dissociation of gases on wustite in the analogous thermogravimetric relaxation method is avoided (42),... 

As explained in the previous chapters, catalysis is a cycle, which starts with the adsorption of reactants on the surface of the catalyst. Often at least one of the reactants is dissociated, and it is often in the dissociation of a strong bond that the essence of catalytic action lies. Hence we shall focus on the physics and chemistry involved when gases adsorb and dissociate on a surface, in particular on metal surfaces. 

While first-order kinetics are observed with most diatomic gases that adsorb in molecular form, dissociative adsorption of gases such as H2 and N2 follows second order kinetics. In the limit of the empty surface the rate of adsorption is... 

Dissociation of the gases SiH4 and H2 by electron impact will create reactive species (radicals) and/or neutrals (Si2H6 and even higher-order silanes [195-198]). Atomic hydrogen is an important particle because it is formed in nearly all electron impact collisions, and the H-abstraction reaction [199, 200] of (di)silane is an important process, as is seen from sensitivity study. Dissociation of SiHa can create different SiH (with x = 0, 1,2, 3) radicals. Only silylene (SiH2) and... 

In a number of cases, the temperature of the filament and thermodynamic parameters allow one to calculate [9] the flux intensity of free atoms produced in dissociation of molecules. Specifically, in the case of dissociation of hydrogen, oxygen, and nitrogen molecules on hot metal filaments under pressures of molecular gases higher than lO" Torr, the flux intensity of atoms A originating from A2 molecules is given by... 

See Kragh, "Between Physics and Chemistry," 27 and Barkan, "Walther Nemst," 158159, drawing on a letter from Ostwald to Nerst, 22 November 1892, Ostwald Papers, AAW, Berlin. The views at issue are found in J. H. van t Hoff, "Role of Osmotic Pressure in the Analogy between Solutions and Gases" (1887) and Svante Arrhenius, "On the Dissociation of Substances in Aqueous Solution" (1887), in The Foundations of the Theory of Dilute Solution (Edinburgh Alembic Club, 1929), no. 19. 

For some reactions, has been determined by direct measurement over a broad range of temperature, pressure, and salinities. Enough data exist to formulate empirical equations that enable extrapolation to the exact temperature, salinity, and pressure of interest. This has been done for the chemical reactions in the carbonate system, for the dissociation of water and for the dissolution of gases. These equations have been used to formulate look-up tables, such as those presented in the online appendix on the companion website. 

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