A binary solution at 107°C contains 50 mol% water (W) and 50 mol% formic acid (F). Using (2-72) with vapor pressure data and the van Laar equation of Table 2.9 with AWF = -0.2935 and

AFW = -0.2757, compute:

(a) The bubble-point pressure.

(b) The dew-point pressure.

Also determine whether the mixture forms a maximum- or minimum-boiling azeotrope. If so, predict the azeotropic pressure at 107°C and the azeotropiccomposition.

Table 2.9 Empirical and Semitheoretical Equations for Correlating Liquid-Phase Activity Coefficients of Binary Pairs Equation for Species 2 Name Equation for Species 1 logyi = Ax logy = Ax} (1) Margules x[21 + 2x2 (12 21)] log yi = xA 12 + 2x1(21 12)] (2) Margules (two-constant) log y2 = A12 A21 In y, = [1 + (x1A12)/(x2A21)] Iny, = -In(x1 + A12x2) In y2 = [1+ (x2A21)/(x1A12)J In y2 = -In (x2 + A21X1) (3) van Laar (two-constant) (4) Wilson (two-constant) A12 A21 A12 A21 +x2 x1 + Aj2x2 x2 + A21X1, -x1 \x1 + A12x2 x2 + A211, xiT12G12 (x2 + XG12)? X3721G21 In y (5) NRTL (three-constant) In y2 = (x1 +X2G21)? (x2 + XG12) (x1 + x,G21) exp(-ajty) = exp (-ajTj) Gij Gij 02 In y, = In X1 In y2 = In- X2 In 2 In (6) UNIQUAC (two-constant) +v (4-) -4, la (0, + 0,T12) +V2 (1 -2) - q In (0, + 02T21) - q2 In (02 + 0, T 12) r2 T21 01 + 02T21 T12 T12 T21 +0291 + 0,92 02 + 0,T12 01 + 02T21. 02 + 0,T12,