Non-spontaneous process

The oxidation of hydrogen to water (Hj -t- i Oj -> HjO) is thermodynamically spontaneous and the energy released as a result of the chemical reaction appears as heat energy, but the decomposition of water into its elements is a non-spontaneous process and can be achieved only by supplying energy from an external source, e.g. a source of e.m.f. that decomposes the water electrolytically. Furthermore, although the heat produced by the spontaneous reaction could be converted into electrical energy, the electrical... 

We now introduce the second law of thermodynamics a physicochemical process only occurs spontaneously if accompanied by an increase in the entropy S. By corollary, a non-spontaneous process - one that we can force to occur by externally adding energy - would proceed concurrently with a decrease in the energetic disorder. 

Any further reaction beyond (eq) would not only fail to liberate any further energy, but also would in fact consume energy (we would start to go uphill on the right-hand side of the figure). Any further increment of reaction would be characterized by AG > 0, implying a non-spontaneous process, which is why the reaction... 

Distinguish between a spontaneous process and a non-spontaneous process and give an example of each. 

Fig. 11.5. Regimes for exothermic, endothermic, spontaneous, and non-spontaneous processes in exergy-enthalpy diagrams.

Fig. 11.6. Reaction vectors in exergy-enthalpy diagrams (a) a non-spontaneous process giving a single reaction vector, (b) coupling and coupled processes leading to a composite reaction vector.

Free energies also provide us with quantitative information about processes. The change in the free energy is equal to the maximum work that can be extracted from a spontaneous process, or in the case of a non-spontaneous processes, the minimum amount of work that is required to cause the process to occur. 

Since the entropy of hydrogenation must be negative, this is a non-spontaneous process under all conditions. A second dehydrogenation reaction, seen in Eq. 

The synthesis of glucose directly from CO2 and H2O and the synthesis of proteins directly from amino acids are both non-spontaneous processes under standard conditions. Yet it is necessary for these to occur for life to exist. In light of the second law of thermodynamics, how can life exist ... 

A spontaneous process occurs by itself, whereas a non-spontaneous process requires a continuous input of energy to make it happen. It is possible to cause a nonspontaneous pro-... 

Some reactions and processes are non-spontaneous, for example copper does not react with dilute hydrochloric acid and water does not freeze (under standard thermodynamic conditions). A non-spontaneous process would result in a decrease in the entropy of the universe. 

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