## Activity coefficients

The activity coefficients yA and yB can be deduced from hex by applying the Gibbs-free-energy analogs of Eqs (7.20a) and (7.20b). Replacing h by g and hi by gi = h in these formulas yields:

dxA dxB

Substituting Eq (7.36) into the above equations and comparing the resulting formulas for and ^ B with those obtained by eliminating the activity between Eqs (7.29) and (7.30) yields:

dhex dhex RTlnyA = hex + xB^— and RTlnyB = hex + xA (7.41)

dxA dxB

The regular solution simplification, gex = hex has been used3. The latter is given by Eq (7.39) and Eq (7.41) reduces to:

Since the interaction parameter Q is not a function of temperature, the logarithm of the activity coefficient varies inversely with temperature. The activity coefficients must satisfy the Gibbs-Duhem equation (Eq (7.31)). Not all hex functions of composition fit this restraint (see problem 7.4). However, problem 7.7 demonstrates that the activity coefficients of Eq (7.42) satisfy the Gibbs-Duhem equation ## Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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