R410a is a replacement for R22 in air conditioners and heat pumps. Air conditioners require a different refrigerant because they operate in a different temperature range. R410a avoids the problems with the ozone layer caused by chlorofluorocarbons, but its longevity may be limited because it has a relatively high global warming factor (1725 times the effect of CO₂). Roughly, it is a 50wt% mixture of difluoromethane (D) and pentafluoroethane (P) (i.e., 70mol% D). Kobayashi and Nishiumi (1998) report a pressure of 1.098 MPa at 283.05K. You may assume the SCVP equation

(a) Assuming k_ij = 0 for the binary interaction parameter of the SSCED equation, predict whether an azeotrope should be expected in this system at 283.05 K. Tabulate the relative volatilities at x_D = 0.01 and 0.99.

(b) Solve for the value of k₁₂ that matches the reported pressure.

(c) What acidity value for pentafluoroethane matches the value of k_ij determined in part (b)?

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Tc(K) PC(MPa) Compound Difluoromethane 351.6 5.83 Pentafluoroethane 342.0 3.44 Cp/R Mw 52.0 120.0 0.273 5.2 0.259 11.4 P298 8(J/cc)¹/2 a(J/cc)¹/2 B(J/cc)¹/2 1.21 1.49 20.67 14.67 5.00 ? 3.00 0.00