Big Chemical Encyclopedia

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

Articles Figures Tables About

Reversion defined

Here p is the number of lines in k > or k >, l is the number of islands formed when the diagrams are superimposed as shown in Fig. 3, and m is the number of arrow reversals defined below. The overlap shown is between a Kekule diagram (dashed... [Pg.653]

A somewhat subtle point of difficulty is the following. Adsorption isotherms are quite often entirely reversible in that adsorption and desorption curves are identical. On the other hand, the solid will not generally be an equilibrium crystal and, in fact, will often have quite a heterogeneous surface. The quantities ys and ysv are therefore not very well defined as separate quantities. It seems preferable to regard t, which is well defined in the case of reversible adsorption, as simply the change in interfacial free energy and to leave its further identification to treatments accepted as modelistic. [Pg.352]

Flere the subscripts and/refer to the initial and final states of the system and the work is defined as the work perfomied on the system (the opposite sign convention—with as work done by the system on the surroundings—is also in connnon use). Note that a cyclic process (one in which the system is returned to its initial state) is not introduced as will be seen later, a cyclic adiabatic process is possible only if every step is reversible. Equation (A2.1.9), i.e. the mtroduction of t/ as a state fiinction, is an expression of the law of conservation of energy. [Pg.330]

Since is defined as work done on the system, the minimum amount of work necessary to produce a given change in the system is that in a reversible process. Conversely, the amount of work done by the system on the surroundings is maximal when the process is reversible. [Pg.342]

In analogy to the constant-pressure process, constant temperature is defined as meaning that the temperature T of the surroundings remains constant and equal to that of the system in its initial and final (equilibrium) states. First to be considered are constant-temperature constant-volume processes (again Aw = 0). For a reversible process... [Pg.346]

For reactions with well defined potential energy barriers, as in figure A3.12.1(a) and figure A3.12.1(b) the variational criterion places the transition state at or very near this barrier. The variational criterion is particularly important for a reaction where there is no barrier for the reverse association reaction see figure A3.12.1(c). There are two properties which gave rise to the minimum in [ - (q,)] for such a reaction. [Pg.1015]

In this paper we present a number of time integrators for various problems ranging from classical to quantum molecular dynamics. These integrators share some common features they are new, they are second-order accurate and time-reversible, they improve substantially over standard schemes in well-defined model situations — and none of them has been tested on real applications at the time of this writing. This last feature will hopefully change in the near future [20]. [Pg.421]

The overpotential is defined as the difference between the actual potential of an electrode at a given current density and the reversible electrode potential for the reaction. [Pg.967]

Chapter 3, there is often a region immediately preceding the lower closure point, in which increased adsorption is brought about by reversible capillary condensation. The meniscus now tends to be somewhat ill defined owing to its small dimensions (p. 153), but the mechanism can still be thought of in Kelvin terms, where the driving force is the pressure difference across an interface. [Pg.244]

Favorable and unfavorable equihbrium isotherms are normally defined, as in Figure 11, with respect to an increase in sorbate concentration. This is, of course, appropriate for an adsorption process, but if one is considering regeneration of a saturated column (desorption), the situation is reversed. An isotherm which is favorable for adsorption is unfavorable for desorption and vice versa. In most adsorption processes the adsorbent is selected to provide a favorable adsorption isotherm, so the adsorption step shows constant pattern behavior and proportionate pattern behavior is encountered in the desorption step. [Pg.263]

The Carnot cycle is formulated directly from the second law of thermodynamics. It is a perfectly reversible, adiabatic cycle consisting of two constant entropy processes and two constant temperature processes. It defines the ultimate efficiency for any process operating between two temperatures. The coefficient of performance (COP) of the reverse Carnot cycle (refrigerator) is expressed as... [Pg.352]


See other pages where Reversion defined is mentioned: [Pg.283]    [Pg.327]    [Pg.126]    [Pg.86]    [Pg.283]    [Pg.327]    [Pg.126]    [Pg.86]    [Pg.160]    [Pg.333]    [Pg.1689]    [Pg.1926]    [Pg.2572]    [Pg.2573]    [Pg.2823]    [Pg.458]    [Pg.615]    [Pg.138]    [Pg.301]    [Pg.350]    [Pg.377]    [Pg.379]    [Pg.222]    [Pg.540]    [Pg.1162]    [Pg.64]    [Pg.67]    [Pg.188]    [Pg.41]    [Pg.352]    [Pg.68]    [Pg.269]    [Pg.284]    [Pg.284]    [Pg.291]    [Pg.385]    [Pg.47]    [Pg.171]   
See also in sourсe #XX -- [ Pg.324 ]




SEARCH



Chemical reversibility defined

Defined reversible

Defined reversible

Electrochemical reversibility defined

Reverse engineering defined

Reverse phase chromatography defined

Reverse rate, defined

Reversible distillation defined

Reversible half-reaction, defined

Reversible process, defined

Reversible stoichiometric reactions defined

Using reversible processes to define the entropy

© 2024 chempedia.info