Spontaneous processes identifying

For each of the following processes, identify the system and the surroundings. Identify those processes that are spontaneous. For each spontaneous process, identify the constraint that has been removed to enable the process to occur ... 

C14-0081. A pair of weights and a pulley can be used as an analogy for a coupled reaction. Use the figure to describe a coupled process. Identify spontaneous and nonspontaneous portions of the process. 

C14-0117. The notion of thermodynamic coupling of a nonspontaneous process with a spontaneous process is not restricted to chemical reactions. Identify the spontaneous and nonspontaneous portions of the following coupled processes (a) Water behind a dam passes through a turbine and generates electricity, (b) A gasoline engine pumps water from a valley to the top of a hill. 

Hence, for an isolated system, the entropy of the system alone must increase when a spontaneous process takes place. The second law identifies the spontaneous changes, but in terms of both the system and the surroundings. However, it is possible to consider the specific system only. This is the topic of the next section. 

Figure 7.4 illustrates the spontaneous process in which heat is transferred from a hotter to a colder body. This process proceeds without outside intervention. The reverse process is never observed. In thermodynamics we need to establish criteria which enable us to identify spontaneity. 

Identify the system and surroundings involved in a spontaneous process and identify the constraint that was removed to enable the process to occur (Section 13.1, Problems 1-2). 

So we have an isolated system divided into two parts each part is initially in its own equilibrium state, as identified by its intensive properties. To initiate a spontaneous process we relax a constraint we remove the partition. Our objective is to test (7.1.18) that is, we want to show that no matter what values are used for the initial temperatures of the gas and alloy, the total entropy never decreases. Note that since one part is a solid, no mass transfer occurs between parts each part is closed. 

Identify each of the processes listed as spontaneous or nonspontaneous. For each nonspontaneous process, describe the corresponding spontaneous process in the opposite direction. ... 

If you let go of a book, it falls to tiie floor because of gravity. At its initial height, it has a higher potential energy than it has when it is on tire floor. Unless it is restrained, tiie book falls and so loses energy. This fact leads us to the first basic principle identifying spontaneous processes and the direction tiiey take Processes in which the aiergy content of the system decreases tend to occur spontaneously. Spontaneous processes tend to be exotiiermic. (Section 5.4, "Strate-... 

The second mechanism is not a spontaneous process that can be identified by the instantaneous evaluation of the flow fields. The clustering is caused by the repelling and attracting periodic interactions with the shear layer vortices and similar to... 

Practice Problem A For each of the following, calculate and identify the process as a spontaneous process, a nonspontaneous process, or an equihbrium process at the specified temperature ... 

Thermodynainics reveals the direction and extent of change for a chemical or physical process, but not the speed at which it occurs. In thCTmodynamics, the word spontaneous merely identifies the direction in which change will occur and should not be taken to inply that it is necessarily fast. 

Oxidation of manganese dioxide to higher valence states takes place in the fusion process of Mn02 and KOH. A tetravalent manganese salt identified as K MnO [12142-27-7] (63) which disproportionates spontaneously is formed. 

A system can in principle undergo an indefinite number of processes under the constraint that energy is conserved. While the first law of thermodynamics identifies the allowed changes, a new state function, the entropy A, is needed to identify the spontaneous changes among the allowed changes. The second law of thermodynamics may be expressed as... 

In view of the last report, it is interesting that Wu et in Beijing have identified an organism, Sinorhizobium morekns S-5, that can convert the hydantoin of racemic -hydroxyphenylglycine into the D-amino acid. This, similar to the process just described, involves a hydantoinase and a carbamoylase, but both appear to be strictly D-specific. These authors again draw attention to the fact that under mildly alkaline conditions, spontaneous racemization of the hydantoin should permit a 100% conversion to the final D-product. 

The preferred route for reducing the molecular weight of PVA involves chain scission at the 1,3-diketone site (see Fig. 6). As the diketone element is chemically not very stable, a spontaneous degradation of oxidised PVA was also discussed [80]. Nevertheless, the preferred degradation pathway is most likely the biochemical process because enzymes were identified that showed high activity with diketone substrates [81], especially with oxidised PVA. The p-diketone hydrolase (BDH EC 3.7.1.7) hydrolyses aliphatic p-diketones to form methyl ketones and carboxylic acids in equimolar amounts [82]. The enzymatic cleavage of C-C bonds in p-diketones is not well studied [83]. BDH enzymes could be isolated from different PVA-degrading strains, purified, characterised and cloned [84]. 

Recently, the PCB-biodegradative capabilities of methanotrophs have been demonstrated (Adriaens, 1994). In this study, 2-CB was oxidized by a methanotrophic culture (CSC1) to a hydroxylated chlorobiphenyl intermediate identified as 2-hydroxy-3-chlorobiphenyl. This intermediate indicated that the metabolite was formed via a concerted oxidation involving an arene oxide which rearranges spontaneously via an NIH shift. No studies have shown, however, that methanotrophs can degrade more highly chlorinated PCBs, and their utility for bioremediation processes does not seem promising. 

It has been shown that 3 is biotransformed in a reaction catalysed by monoamine oxidase B to species that cause the selective degeneration of nigrostriatal neurons, giving rise to a Parkinsonian syndrome in man and other primates. Studies of this process have shown that the pyridinium salts 4 and 5 are involved, and that 4 undergoes spontaneous disproportionation to 5 and 3 5 is the putative ultimate neurotoxin. More recent studies have shown that 4 undergoes a spontaneous reaction in pH 7.4 buffer to give methylamine and a product identified as 6. 

---