Entropy driven distribution

In purely ionic compounds, the conductivity from these mechanisms is intrinsic and relates only to the entropy-driven Boltzmann distribution the conductivity will thus increase with increase in temperature. Because the number of defects is quite limited, the conductivities are low, of the order of I0-6 ft 1 cm-1. In addition, extrinsic vacancies will be induced by ions of different charge (see page 264). There exist, however, a few ionic compounds that as solids have conductivities several orders of magnitude higher. One of the first to be studied and the one with the highest room-temperature conductivity, 0.27 fl-1 cm-1, is rubidium silver iodide, RbAg j.1 1... 

So far, we have tentatively assumed that all molecules and particles are randomly distributed throughout the volume available. If there are two (or more) substances present, say solute and solvent, concentration differences can occur for a number of reasons. If so, the heat motion causes the molecules to attain a (more) random distribution, i.e., the concentration differences will eventually disappear, except over very small distances. The process is thus entropy driven. The rate at which it occurs is generally described by Fick s laws. Fick postulated in his first law that the diffusional transport rate is proportional to the concentration gradient according to... 

In purely ionic compounds, the conductivity fbom these mechanisms is intrinsic and relates only to the entropy-driven Boltzmann distribution the conductivity will thus increase with increase in temperature. Because the number of defects is quite... 

Shubert VA, Baquero EE, Clarkson JR, James WH, Turk JA, Hare AA, Worrel K, Lipton MA, Schofield DP, Jordan KD, Zwier TS (2007) Entropy-driven population distributions in a prototypical molecule with two flexible side chains 0-(2-acetamidoethyl)-N-acetyltyramine. JChemPhys 127 234315... 

Nonequilibrium Steady State (NESS). The system is driven by external forces (either time dependent or nonconservative) in a stationary nonequilibrium state, where its properties do not change with time. The steady state is an irreversible nonequilibrium process that cannot be described by the Boltzmann-Gibbs distribution, where the average heat that is dissipated by the system (equal to the entropy production of the bath) is positive. 

Polymers are mixtures of macromolecules of different molecular weight, and most commercially available products have rather broad distribution of the molecular weight. Some studies were carried out with fractions of a narrow distribution of the molecular weight, separated from commercially available polymers. Adsorption leads to fractionation as discussed above for some types of surfactants. Larger polymer molecules have higher affinity to the surface than smaller molecules composed of the same type of monomeric units. The selectivity is chiefly driven by the difference in the entropy of mixing in solution. Polydispersity of polymers is also one of the factors responsible for hysteresis loops in the adsorption-desorption cycles. 

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