Introduction entropy change

With the introduction of these relations into Eq. (41), the configurational entropy change (the entropy of mixing solvent and polymer excluded see Chap. XII) relative to the initial state ax = ay = az = l becomes... 

While the first law allows us to calculate the energy change associated with a given process, it says nothing about whether or not the process itself will take place spontaneously. This is the province of the second law of thermodynamics and leads to the introduction of another state function, entropy, S. The entropy change in a system which moves from state 1 to state 2 is defined by... 

The introduction of the superscript (n, V) implies the adoption of a Gibbs convention algebraically expressed by Equations 5, which state that we are comparing the real system with a fictitious one consisting of two bulk phases in contact in the absence of an interfacial region, and with the added specification that the numbers of moles n and the total volume V of the fictitious system shall be the same as in the real one. The quantity S(r 7) (which is called SA° by Guggenheim (3) and sf by Defay (1)) is the entropy change per unit area of interface created when... 

For the polymerization to proceed spontaneously, AG < 0. But AS < 0, because the system evolves to a more ordered state (the number of configurations in which free monomers may be placed in space decreases by the introduction of covalent bonds among themselves) thus, the entropy change does not favor polymerization. Then, the only possibility of getting AG < 0 is to have a significantly exothermic reaction (AH < 0) to counterbalance the unfavorable entropy change. 

The adsorption system considered is open and exchanges heat and matter with the surroundings. Under these conditions, during the introduction of an infinitesimal amount of adsorptive, dn (taken at temperature T and pressure p), using the second law of thermodynamics, the entropy change of the system may be written as... 

Rouquerol et al. (11, 12) have recently described the experimental determination of entropies of adsorption by applying thermodynamic principles to reversible gas-solid interactions. Theoretically, the entropy change associated with the adsorption process can only be measured in the case of reversible heat exchange. The authors showed how isothermal adsorption microcalorimetry can be used to obtain directly and continuously the integral entropy of adsorption by a slow and constant introduction of adsorbate under quasi-equilibrium conditions (11) or by discontinuous introduction of the adsorbate in an open system (12). 

The actual values depend on the entropy change between the states, a fector we have conveniently ignored in this oversimplified introduction to the loss process. Inclusion of the entropy term into the free energy produces a set of curves which are slightly displaced from one another, but have essentially the same shape. 

The concentration of Schottky defects in a binary salt MX can be readily calculated. From Equation (3.12) it can be seen that the configurational entropy change for introduction of a Schottky pair of anion and cation vacancies is... 

In the reported examples, an isothermal microcalorimeter with a discontinuous (stepwise) introduction of the adsorptive was fmitfully employed. An alternative, suitable way to collect the experimental data required for determining the enthalpy and entropy changes accompanying the adsorption process is to follow the procedure implying the slow-and-constant adsorptive introduction which was extensively described in Ref. [99]. 

This change in the behavior of the simulation is counterintuitive. One would expect the introduction of greater uncertainty in the transition rules to increase the entropy of the system, but it has the opposite effect, leading to... 

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