Created entropy

Distinguishing the created entropy deSrev from the transferred entropy dtSirT, we express the total change in entropy as the sum of the two parts shown in Fig. 3.2 and Eq. 3.12 ... 

This indicates that any irreversible process, if occurring at constant entropy S and pressure p, is accompanied by a decrease in the enthalpy from the initial high level Hjnijal toward the final low level Hfiml of the system. From the foregoing we see that the internal energy and enthalpy may play the role of thermodynamic potentials for an irreversible process if occurring under the condition of constant entropy S. This condition of constant entropy, however, is unrealistic because entropy S contains both created entropy Sirr and transferred entropy Sm. 

The mixing of substances is an irreversible process that takes place creating entropy in the system. The entropy thus created is defined as the entropy of mixing SM. Suppose two different ideal gases with different volumes Vl and V2 are mixed isothermally at a constant pressure p to make a single mixture system with a volume V, + V2 as shown in Fig. 3. 10. The overall entropy S1 of both individual systems before the mixing is obtained from Eq. 3.47 as shown in Eq. 3.49 ... 

The affinity of irreversible processes is a thermodynamic function of state related to the creation of entropy and uncompensated heat during the processes. The second law of thermodynamics indicates that all irreversible processes advance in the direction of creating entropy and decreasing affinity. This chapter examines the property affinity in chemical reactions and the relation between the affinity and various other thermodynamic quantities. 

Formation of the chelate releases six NH3 molecules so that the total number of particles increases from four to seven. This creates entropy, and so favors the chelate form. Each chelate ring usually leads to an additional factor of about 10 in the equilibrium constant for reactions like equation (1). Equilibrium constants for complex formation are usually called formation constants the higher the value the more stable the complex. 

The inequality (3.4) states that the creation of entropy is always positive, that is to say irreversible processes can only create entropy, they cannot destroy it. We note that for an isolated system... 

Irreversible phenomena can create entropy but cannot destroy it, P. Van Rysselberghe, Chem. Rev, 16, 29, 37 (1935). 

The increase in availability, AS, is entirely determined by the initial and final states of the materials, together with the temperature and pressure of the medium (infinite surroundings). However the engineer still retains the liberty to make a (created entropy), and therefore w, (total equivalent work requirement of the process), as small as possible. This requires a suitable choice of the path between the given initial and final states, i.e. the choice of the details of the operation. 

Again, starting at state (A), via process (3) we mix cis-2-butene and trans-2-butene to obtain state (D). Obviously, the process (3) creates entropy of mixing. Then, in the mixture we transform cis-2-butene into lrans-2-butene via process (4). Then, in state (C) we have pure lran5 -2-butene in the combined chamber. 

Next, we mix the ds-2-butene formed in this region with the rrans-2-butene in the rest of the system. This process creates entropy of mixing. 

If we think the reverse process (4r) now in the normal (forward) way (4), then we separate first the mixture and then convert one component. By means of the separation process, the entropy of mixing that is created in process (3) is compensated. The separation process creates entropy of de-mixing, which is just the reverse of mixing. 

Returning to the former case, the irreversibility lies in the fact that the system has been restored to its original condition only at cost of transferring heat from it into a heat bath. Thus the inevitable result of an irreversible process is the creation of entropy, and the system can be restored to its original condition only by the removal of heat. That is to say, the created entropy must be transferred to some other body, such as a heat bath, w hich thereby undergoes a... 

Since cr, the created entropy, cannot be negative, the useful work obviously has its maximum value when reversible operation of the process. The quantity T or may be called the irreversibility of the process, or alternatively the dissipated energy or the wasted work. In any industrial process it is obviously desirable to reduce it as far as is possible by an approach to reversible conditions. 

In his famous book on quantum mechanics, Dirac stated that chemistry can be reduced to problems in quantum mechanics. It is true that many aspects of chemistry depend on quantum mechanical formulations. Nevertheless, there is a basic difference. Quantmn mechanics, in its orthodox form, corresponds to a deterministic time-reversible description. This is not so for chemistry. Chemical reactions correspond to irreversible processes creating entropy. That is, of course, a very basic aspect of chemistry, which shows that it is not reducible to classical dynamics or quantum mechanics. Chemical reactions belong to the same category as transport processes, viscosity, and thermal conductivity, which are all related to irreversible processes.. .. [A]s far back as in 1870 Maxwell considered the kinetic equations in chemistry, as well as the kinetic equations in the kinetic theory of gases, as incomplete dynamics. From his point of view, kinetic equations for... 

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