If the chemical reaction proceed by the combination and evaporation of molecules from m adjacent spaces the velocity of chemical change will be given by [Pg.152]

A crystal of iodine in an evacuated vessel will gradually change into iodine gas by the evaporation of molecules from its surface. Occasionally one of these free gas molecules will again strike the surface of the crystal, and it may stick to the surface, held by the van der Waals attraction of the other crystal molecules. This is called condensation of the gas molecules. [Pg.40]

From a kinetic point of view, a cluster is formed and changes its size by the condensation and evaporation of molecules. At a given temperature, the evaporation rate of molecules (per unit time and unit area) is independent of S, but determined primarily by i, while [Pg.586]

For diatomic molecules and polyatomic molecules generally, the moment of inertia appears in the integration constant of the vapour-pressure equation, because the existence of rotations in the gas, while there are usually none in the solid, favours the evaporation of molecules by offering more possibilities of distribution in the gas phase. The greater the moment of inertia, the smaller the rotational quantum and the more numerous the levels. Hence the increase of i with I revealed in the formula. [Pg.143]

Any valid chemical model of adsorption should predict an equation that accurately describes the experimental adsorption isotherm. In 1918, Langmuir developed a kinetic model of adsorption that described vapor adsorption on a homogeneous surface. The surface is assumed to possess a certain number of identical sites, S. Of these sites, Sa are occupied by adsorbate molecules and So = S — Sa are vacant. The rate of evaporation of molecules from the surface is reasoned to be proportional to S because all molecules are adsorbed with the same bond strength on identical sites (adsorbate molecules on adjacent sorption sites are assumed not to interact). Thus, each molecule has an equal chance of desorbing from the surface in any particular time period. Mathematically, this means that [Pg.345]

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