Kinetic energy temperature effects

Kinetic and design calculations for reactors require information on the rate of reaction and equations lo describe the concentration, temperature, and/or pressure variation within the reactor. Part I develtjped equations to describe the rate of a chemical reaction and qualitatively discussed energy (temperature) effects plus phase and chemical equilibrium. The contents of Part I can be combined and the results applied to the three major classifications for reactors to be addressed later. 

The rates of these reactions bodr in the gas phase and on the condensed phase are usually increased as the temperature of die process is increased, but a substantially greater effect on the rate cati often be achieved when the reactants are adsorbed on die surface of a solid, or if intense beams of radiation of suitable wavelength and particles, such as electrons and gaseous ions with sufficient kinetic energies, can be used to bring about molecular decomposition. It follows drat the development of lasers and plasmas has considerably increased die scope and utility of drese thermochemical processes. These topics will be considered in the later chapters. 

Having this view of the make-up of the heat content of a substance, we can now visualize the effects brought on by warming the substance. If the temperature is low at first, the substance will be a solid. Warming the solid increases the kinetic energy of the back-and-forth motions of the molecules about their regular crystal positions. As the temperature rises, these motions disturb the regularity of the crystal more and more. Too much of this random movement destroys the lattice completely. At the temperature... 

Fig. 8-4. Effect of temperature on atomic (or molecular) kinetic energy distribution.

Kinetic, energy, 24 theory of dissipation, 87 theory of gases, 515 theory of solids, 517 theories in thermodynamics, 513 Kirchoff s equation for effect of temperature, 112, 259 equations for vapour-pressure, 179, 190, 192, 390, 412 Konowalow s theorem, 385, 407 vapour-pressure curves, 382... 

In addition to the effects discussed above, two further possible sources of discrimination peculiar to ion-molecule reactions must be considered. First, although it is known that most primary ions are formed without kinetic energy, such may not be the case for ions produced by ion molecule reactions. Secondary ions formed in exothermic ion-molecule reactions could retain a considerable fraction of the exo-thermicity as kinetic energy and diffuse from the sampling region at a rate considerably greater than predicted from the ambient temperature. The limited evidence to date (40) indicates that the kinetic energy of the product ions is small, but this may not be true for all types of reactions. 

To complete our analysis, we must determine the effect of a change in temperature. According to Equation, kinetic energy is proportional to temperature, and according to Equation, kinetic energy is proportional to the square of the molecular speed. Thus, the square of the molecular speed is proportional to temperature. 

---