The Fugacity of Pure Gases

Example 7.1 shows the calculation of the fugacity of pure gases. 

Example 7.1 Estimate the fugacity of propane gas at 220°F and 500 psia. We will proceed in several ways, showing several possibilities. 

We then perform the integration by trapezoid rule, finding 

FUGACITY, IDEAL SOLUTIONS, ACTIVITY, ACTIVITY COEFFICIENT 

FIGURE 7.2 Compressibility factor z for propane gas at three temperatures and along the saturation curve. Data from [2], 

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Equation 7-14 is used to calculate the reference state fugacity of liquids. Any equation of state can be used to evaluate ([) . For low to moderate pressures, the virial equation is the simplest to use. The fugacities of pure gases and gas mixtures are needed for estimating many thermodynamic properties, such as entropy, enthalpy, and fluid phase equilibria. For pure gases, the fugacity is... 

In current industrial practice, we almost always estimate the fugacity of pure gases from an EOS. For simple estimates, we use a simple EOS the computer programs that compute and use such fugacity data normally use complex EOSs, which are more accurate than simple EOSs like the little EOS. 

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