Vaporization free energy change

The Unitary Part of a Free Energy Change. In this way we can obtain values for the unitary terms characteristic of processes of each of the four types discussed in Chapters 1 and 2. At this point it will be convenient to review what was said in those chapters and to relate that discussion to (71) and (72). In Sec. 11 the dissociation energy D was introduced by analogy with the dissociation energy T3tac, defined for the Bame molecule in a vacuum. In solution (as in a gas or vapor) the parts... 

The standard Gibbs free energy change per mole accompanying vaporization (the conversion of a substance from the liquid state into the vapor state), standard hydrogen electrode (SHE) A hydrogen... 

The trapping efficiency of polymeric, microporous adsorbents [e.g., polystyrene, polyurethane foam (PUF), Tenax] for compound vapors will be affected by compound vapor density (i. e., equilibrium vapor pressure). The free energy change required in the transition from the vapor state to the condensed state (e.g., on an adsorbent) is known as the adsorption potential (calories per mole), and this potential is proportional to the ratio of saturation to equilibrium vapor pressure. This means that changes in vapor density (equilibrium vapor pressure) for very volatile compounds, or for compounds that are gases under ambient conditions, can have a dramatic effect on the trapping efficiency for polymeric microporous adsorbents. 

The discussion of moisture uptake by hygroscopic materials must include a description of the thermodynamics of vapor-liquid equilibria. For gas (g) and liquid (1) phases to be in equilibrium, the infinitesimal transfer of molecules between phases (dng and dn ) must lead to a free energy change of zero. 

In order to derive the Kelvin equation on thermodynamic grounds, consider the transfer of d moles of vapor in equilibrium with the bulk liquid at pressure Pq into a pore where the equilibrium pressure is P. This process consists of three steps evaporation from the bulk liquid, expansion of the vapor from Pq to P and condensation into the pore. The first and third of these steps are equilibrium processes and are therefore accompanied by a zero free energy change, whereas the free energy change for the second step is described by... 

When the adsorbate condenses in the pore it does so on a previously adsorbed film thereby decreasing the film-vapor interfacial area. The free energy change associated with the filling of the pore is given by... 

Method of Amidon and Anik The method of Amidon and Anik [9] applicable to hydrocarbons and is based on the group additivity of the surface area. The approach is to model the Gibbs free energy change for the vaporization process, AGV, as an additive parameter according to the following equation ... 

AGv Gibbs free energy change for vaporization process... 

When a liquid and its vapor are in equilibrium, there is no tendency for one phase to change into another. In the language of Section 7.11, the free energy change for the formation of vapor from liquid is 0 when the two phases are in equilibrium ... 

M. Trautz and W. Gerwig obtained different values and represented their results by log p——1332T-1+7-867 mm. They gave 5-35 Cals, for the mol. heat of vaporization while E. Briner and Z. Pylkoff gave A=5-56 Cals., or A/T=9-5 log T —0-007T. M. Trautz and C. F. Hinck calculated the heat of formation to be 18 Cals. and G. N. Lewis and M. RandalL the free energy change, between 500° K. and 750° K to be -9100+14 3T. 

It is above Kp f which are listed for the equilibrium constants of formation when a condensed phase is present. Kp, f is determined from the standard free energy change of the gaseous system and the vapor pressure of the condensed phase. 

That is, the activated low-pressure vapor deposited diamond process has been quantitatively verified as an example of thermodynamic reaction coupling, because all these data of molar Gibbs free energy changes are subordinate to criterion in modem thermodynamics for reaction coupling, i.e. [(AGOt > 0, (AG2)t p < 0 and (AG)t p<0]. 

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