Question

3. Consider the hexafluorobenzene(1)-cyclohexane(2) mixture at 50 °C. The vapor pressures for the pure species are psat = 34.10 kPa and Pat = 36.30 kPa. a. (10%) Assuming Raoult's law, calculate the pressure range of the 2-phase region when the mole fraction of hexaflourobenzene is 0.8. b. (10%) Experiments show that this mixture at 50°C has an azeotrope. Show mathematically that Raoult's law is unable to predict an azeotropic behavior. c. (10%) Use the modified Raoult's law with the van Laar equation to find the composition and calculate the pressure at the azeotrope. The van Laar coefficients for this system are L12 1.1830 and L21 0.9887

Answer 1

Sol AT T-50°C - Pisa -34-10 upe 235-3630 KPo. 0) 4=0.8. From Roults low Roults Low Pia Rip Pr = P +P Pi= riPitxo P Paz 08634-10 +0-9 136-30 .. :7oou 70 =0.834:10 Pr=97:58+ 736=134.54 upe b) If 50°C form Axeotop then x=y, From Routs low y, Pr = 14 PM 10-789 34.64 c) from Modiped Raudts low lyi P, = 4 x PM From Venlor Egn. Luxe = Arf (Han Auto 4,95 Ang An 14 Arlxr. Aru Hi=1:0359 >) 0.0353 Air=1-183 Adi = 009007: Anyi- 1.193 (1+1,183.0.2 onostood QºBar = 0.676 of Y> = 10966. 0.9807 Ing= 0.48020-2 ( 1+(0,3185

•o354xo •4x 39 | 4 • 554 к?. р, Р. - 1966 xos): 362 (1-22 КР 2 - °ч +7, N, P," t Gahlt ble ore - Ч-55 Р. l y= Di 99•o | - Бsk-, - Esilh Р Я» = 0-39
using roluts law and given vapor pressure data we can find the required variables

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