Entropy atom combination

As the atoms or ions vibrate in a solid, the uncertainty in the exact value of their energy constitutes thermal entropy, Sf. Combining 5.4 and 5.7 it follows that ... 

The entropy change is also negative when hydrogen atoms combine, because the atoms have a less ordered arrangement than the molecules ... 

The entropy of atom combination, is the change in entropy when a mole of a substance is produced from its constituent atoms in the gas phase at 1 atmosphere pressure and 25 °C. 

Table 1. Standard state entropies of atom combination,...

Why do the entropies of atom combination generally become more negative as the number of atoms in the molecule increases ... 

Why are the entropies of atom combination more negative for liquids than the corresponding entropies of atom combination for gases ... 

To perform this calculation, we need a table of values of the entropies of atom combination for a variety of species. We have seen that the entropy change associated with a process can depend upon temperature and pressure. In addition, entropy changes depend on concentration changes that occur in solution, Thus, we need to define a set of refeence conditions, called standard state conditions, at which measurements are made. By convention, the standard state conditions for thermodynamic measurements are ... 

Use enthalpies of atom combination and entropies of atom combination to determine if any of the following reactions have an equilibrium constant greater than 1. Find the reaction with the greatest equilibrium constant. Find the reaction with the smallest equilibrium constant. 

TABLE A.3 Standard-State Enthalpies, Free Energies, and Entropies of Atom Combination... 

Attempts have been made to account for the rate enhancements in intramolecular catalysis on the basis of an effective concentration of 55 M combined with the requirement of very precise alignment of the electronic orbitals of the reacting atoms orbital steering. Although this treatment does have the merit of emphasizing the importance of correct orientation in the enzyme-substrate complex, it overestimates this importance, because, as we now know, the value of 55 M is an extreme underestimate of the contribution of translational entropy to effective concentration. The consensus is that although there are requirements for the satisfactory overlap of orbitals in the transition state, these amount to an accuracy of only 10° or so.23-24 The distortion of even a fully formed carbon-carbon bond... 

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