Chemical change entropy

The tight and loose transition-state hypothesis is in contrast with the assumption that there is extensive cancellation of contributions due to chemical change in the entropic component of the EM (p. 81). Indeed, the uniform behaviours displayed by 0AS-data for reactions widely differing in nature (Figs 5, 23, and 24) clearly shows that no matter how loose a transition state or product is, the entropy contribution from such looseness will be cancelled out extensively by virtue of the operator 0. 

Alhassid, Y., and Levine, R. D. (1977), Entropy and Chemical Change IU The Maximal Entropy (Subject to Constraints) Procedure as a Dynamical Theory, J. Chem. Phys. 67, 4321. 

The process shown in Figure 7.5 is certainly a favourable change. Yet no exchange of energy is involved. The condition that influences this change is called entropy. It is an important condition in all physical and chemical changes. 

What does entropy have to do with favourable chemical changes and equilibrium systems All favourable changes involve an increase in the total amount of entropy. Recall the endothermic reaction in Figure 7.4. 

O O Write a short paragraph, or use a graphic organizer, to show the relationship among the following concepts favourable chemical change, temperature, enthalpy, entropy, free energy. 

The second law of thermodynamics can be expressed in terms of another state function, the entropy (S). The thermodynamics definition considers the change in entropy dS that occurs as a result of a physical or chemical change, and is based on the expression... 

With the above caveat in mind, it is not difficult to understand that unimole-cular reactions can be activated by ambient blackbody radiation. This has been experimentally reported [44], Moreover, in this perspective, a chemical change would be closely related to a change (increase) in entropy via population variations in an ensemble. 

Entropy production during chemical change has been interpreted [7] as the result of resistance, experienced by electrons, accelerated in the vacuum. The concept is illustrated by the initiation of chemical interaction in a sample of identical atoms subject to uniform compression. Reaction commences when the atoms, compacted into a symmetrical array, are further activated into the valence state as each atom releases an electron. The quantum potentials of individual atoms coalesce spontaneously into a common potential field of non-local intramolecular interaction. The redistribution of valence electrons from an atomic to a metallic stationary state lowers the potential energy, apparently without loss. However, the release of excess energy, amounting to Au = fivai — fimet per atom, into the environment, requires the acceleration of electronic charge from a state of rest, and is subject to radiation damping [99],... 

For book-keeping purposes the production of entropy during chemical change is considered as reducing the useful energy of the system by disorderly dispersion. In many cases this waste can be calculated statistically from the increase in disorder. To be in line with other thermodynamic state functions, any system is considered to be in some state of disorder at all temperatures above absolute zero, where entropy vanishes. 

Although chemists deal primarily with the chemical changes of matter, physical changes are also very important. In this section we will consider how the entropy of a substance depends on its temperature and on its physical state. 

The Creation of Entropy in Physico-chemical Changes in Uniform Systems. 

The ease of dissolution of a solute depends on two factors (1) the change in energy and (2) the change in disorder (called entropy change) that accompanies the process. In the next chapter we will study both of these factors in detail for many kinds of physical and chemical changes. For now, we point out that a process is favored by (1) a decrease in the energy of the system, which corresponds to an exothermic process, and (2) an increase in the disorder, or randomness, of the system. 

If the system be isolated in this case, dQ is again zero and therefore dS > o, i e the entropy increases as a result of the physical or chemical change occurring spontaneously in the isolated system To cover both >... 

Some of the previous articles have inspired several investigations on the relation between entropy and chemical change. In work by Bernstein and Levine (1972) optimal means of characterizing the distribution of product energies were discussed in terms of an information measure / (see e.g. Jaynes, 1963, Katz. 1967 for uses of 1 in thermodynamical problems). Global, detailed experiments provide average transition probabilities ru(A, B), from which the surprisal A, B) is defined to be... 

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