Fugacity of compound

Fig. 6.2 Conceptualization of the fugacity of a compound in a nonideal liquid mixture when gas and hquid phases are in equilibrium (Schwarzenbach et al. 2003)...

Let us now continue with our discussion of how to relate the chemical potential to measurable quantities. We have already seen that the chemical potential of a gaseous compound can be related to pressure. Since substances in both the liquid and solid phases also exert vapor pressures, Lewis reasoned that these pressures likewise reflected the escaping tendencies of these materials from their condensed phases (Fig. 3.9). He thereby extended this logic by defining the fugacities of pure liquids (including subcooled and superheated liquids, hence the subscript L ) and solids (subscript s ) as a function of their vapor pressures, pil ... 

If we consider, for example, compound i in a liquid mixture, e.g., in organic or in aqueous solution (subscript t see Fig. 3.9pure liquid compound by [note that for convenience, we have chosen the pure liquid compound (superscript ) as our reference state] ... 

Figure 3.9 Conceptualization of the fugacity of a compound i (a) in an it/ea/ gas (h) in a pure liquid compound i (c) in an Wen/ liquid mixture and (d) in a nonideal liquid mixture (e.g., in aqueous solution). Note that in (b), (c), and (d), the gas and liquid phases are in equilibrium with one another.

The aqueous solubility of a gaseous compound is commonly reported for 1 bar (or 1 atm = 1.013 bar) partial pressure of the pure compound. One of the few exceptions is the solubility of 02 which is generally given for equilibrium with the gas at 0.21 bar, since this value is appropriate for the earth s atmosphere at sea level. As discussed in Chapter 3, the partial pressure of a compound in the gas phase (ideal gas) at equilibrium above a liquid solution is identical to the fugacity of the compound in the solution (see Fig. 3.9d). Therefore equating fugacity expressions for a compound in both the gas phase and an equilibrated aqueous solution phase, we have ... 

However, biomagnification factors significantly different from 1 may also reflect real processes building up the effective concentrations in a given organism s tissues. Said more accurately, the chemical activity or fugacity of the compound may prove to be greater as one moves up the food chain ... 

Why is it useful to compare the activities or fugacities of a given compound in various environmental compartments ... 

Explain in words how you calculate the activity or fugacity of a given compound in a given environmental compartment (e.g., water, sediment, lipid components of an organism, etc.). What are the major problems encountered when calculating (or estimating) fugacity values ... 

TABLE 8.2.1 Summary of physical properties of Compound some chlorinated dioxins Molecular CAS no. formula Molecular weight, MW g/mol m.p. °C U 0 C Fugacity ratio, F at 25°C Molar volume, VM cm3/mol from p(a) Le Bas ... 

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