Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Subject proportional energy

The Langmuir-Hinshelwood picture is essentially that of Fig. XVIII-14. If the process is unimolecular, the species meanders around on the surface until it receives the activation energy to go over to product(s), which then desorb. If the process is bimolecular, two species diffuse around until a reactive encounter occurs. The reaction will be diffusion controlled if it occurs on every encounter (see Ref. 211) the theory of surface diffusional encounters has been treated (see Ref. 212) the subject may also be approached by means of Monte Carlo/molecular dynamics techniques [213]. In the case of activated bimolecular reactions, however, there will in general be many encounters before the reactive one, and the rate law for the surface reaction is generally written by analogy to the mass action law for solutions. That is, for a bimolecular process, the rate is taken to be proportional to the product of the two surface concentrations. It is interesting, however, that essentially the same rate law is obtained if the adsorption is strictly localized and species react only if they happen to adsorb on adjacent sites (note Ref. 214). (The apparent rate law, that is, the rate law in terms of gas pressures, depends on the form of the adsorption isotherm, as discussed in the next section.)... [Pg.722]

Matter itself has energy, called rest energy. Wliat distinguishes matter-energy from other forms of energy is that all matter has inertia and is subject to the force of gravity when at rest as well as when in motion. Inertia measures the resistance of an object to being accelerated by a force, and the inertia of an object at rest is proportional to its mass. [Pg.776]

In order to relax 1 mol of compacted polymeric segments, the material has to be subjected to an anodic potential (E) higher than the oxidation potential (E0) of the conducting polymer (the starting oxidation potential of the nonstoichiometric compound in the absence of any conformational control). Since the relaxation-nucleation processes (Fig. 37) are faster the higher the anodic limit of a potential step from the same cathodic potential limit, we assume that the energy involved in this relaxation is proportional to the anodic overpotential (rj)... [Pg.380]

The probability density for a particle at a location is proportional to the square of the wavefunction at that point the wavefunction is found by solving the Schrodinger equation for the particle. When the equation is solved subject to the appropriate boundary conditions, it is found that the particle can possess only certain discrete energies. [Pg.145]

On this basis the porosity and surface composition of a number of silicas and zeolites were varied systematically to maximize retention of the isothizolinone structures. For the sake of clarity, data is represented here for only four silicas (Table 1) and three zeolites (Table 2). Silicas 1 and 3 differ in their pore dimensions, these being ca. 20 A and 180 A respectively. Silicas 2 and 4, their counterparts, have been calcined to optimise the number and distribution of isolated silanol sites. Zeolites 1 and 2 are the Na- and H- forms of zeolite-Y respectively. Zeolite 3 is the H-Y zeolite after subjecting to steam calcination, thereby substantially increasing the proportion of Si Al in the structure. The minimum pore dimensions of these materials were around 15 A, selected on the basis that energy-minimized structures obtained by molecular modelling predict the widest dimension of the bulkiest biocide (OIT) to be ca. 13 A, thereby allowing entry to the pore network. [Pg.89]

The CPA [188], marketed by ThermoMetric AB (Sweden), is frequently used in Europe. It operates on the principle of power compensation, which is based on the supply or withdrawal of heat to and from the reactor, respectively, in order to keep the temperature at the set-point and, thus, to compensate for energy differences (either shortage or surplus). The heat is supplied or withdrawn by means of special (Peltier) elements, which produce a cold or a hot surface area if subjected to an electrical current. An accurate measurement of the heat supply/withdrawal is possible as the heat flow is directly proportional to the current supplied to the Peltier elements. [Pg.121]

Note that at spectral equilibrium the integral in (A.33) will be constant and proportional to ea (i.e., the scalar spectral energy transfer rate in the inertial-convective sub-range will be constant). The forward rate constants a j will thus depend on the chosen cut-off wavenumbers through their effect on (computationally efficient spectral model possible, the total number of wavenumber bands is minimized subject to the condition that... [Pg.387]

Another interesting application of the total energy approach involves superconductivity. For conventional superconductors, the 1957 theory of Bardeen, Cooper and Schrieffer [26] has been subject to extensive tests and has emerged as one of the most successful theories in physics. However, because the superconducting transition temperature Tc depends exponentially on the electron-phonon coupling parameter X and the electron-electron Coulomb parameter p, it has been difficult to predict new superconductors. The sensitivity is further enhanced because the net attractive electron-electron pairing interaction is proportional to X-p, so when these parameters are comparable, they need to be determined with precision. [Pg.261]

In many physicochemical interactions which are subject to the same intrinsic mechanism, the free energy change is proportional to the enthalpy. [Pg.101]

No instance is known in which the rate of reaction is proportional to a power of the light intensity greater than the first. It is, indeed, very improbable that a molecule would remain in a condition where it possessed so large an excess of energy as a quantum of visible light long enough to acquire a second quantum, since all the time it would be subject to collisions which would rapidly deprive it of its first quantum. Probably all photochemical transformations are one-quantum processes. [Pg.75]

Several theories have been proposed to explain the mechanisms involved in an AFID system (31). In general, thermal energy is required to atomize a particular alkali metal salt. The alkali metal atoms formed ionize and are subjected to an electric field. This produces a current proportional to the number of ions. The presence of halogen, phosphorus, and even nitrogen enhance the signal. The system is complex and does not lend itself to a complete theory as intricate surface phenomena are possible. In addition, there is speculation that photochemical processes occur and realization that combustion products formed in the flame can interact to form a multitude of species compound the difficulty. It has been proven that the process does depend on thermal energy and not strictly speaking on the products of combustion. For this reason many researchers prefer the term thermionic ionization. [Pg.270]


See other pages where Subject proportional energy is mentioned: [Pg.50]    [Pg.830]    [Pg.496]    [Pg.504]    [Pg.50]    [Pg.504]    [Pg.146]    [Pg.763]    [Pg.76]    [Pg.67]    [Pg.224]    [Pg.535]    [Pg.536]    [Pg.113]    [Pg.228]    [Pg.479]    [Pg.647]    [Pg.296]    [Pg.134]    [Pg.203]    [Pg.302]    [Pg.114]    [Pg.175]    [Pg.165]    [Pg.221]    [Pg.151]    [Pg.222]    [Pg.719]    [Pg.817]    [Pg.1155]    [Pg.283]    [Pg.4]    [Pg.171]    [Pg.487]    [Pg.1020]    [Pg.418]    [Pg.776]    [Pg.780]    [Pg.1587]    [Pg.400]   
See also in sourсe #XX -- [ Pg.2 , Pg.2 , Pg.2 , Pg.4 , Pg.7 ]




SEARCH



Subject energy

© 2024 chempedia.info