Use the virial equation to consider a mixture of propane and n-butane at 515 K at pressures between 0.1 and 4.5 MPa. Verify that the virial coefficient method is valid by using Eqn. 7.10.

(a) Prepare a plot of fugacity coefficient for each component as a function of composition at pressures of 0.1 MPa, 2 MPa, and 4.5 MPa.

(b) How would the fugacity coefficient for each component depend on composition if the mixture were assumed to be ideal, and what value(s) would it have for each of the pressures in part (a)? How valid might the ideal-solution model be for each of these conditions?

(c) The excess volume is defined as

where V_i is the molar volume of the mixture, and Vi is the pure component molar volume at the same T and P. Plot the prediction of excess volume of the mixture at each of the pressures from part (a). How does the excess volume depend on pressure?

(d) Under which of the pressures in part (a) might the ideal gas law be valid?

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Subject to T, > 0.686 +0.439P, or V₂ > 2.0 7.10