Exam+2_Solution-cs

# Exam+2_Solution-cs - #1(15 points a(7 pts A temperature...

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#1 (15 points) a) (7 pts) A temperature of -10 °C is expected over night. How much antifreeze (ethylene glycol, C 2 O 2 H 6 , M = 62 g/mol) do you have to add to 1 L of water to prevent the window wash fluid in your car from freezing ( ∆ܪ ௠,௪௔௧௘௥ ൌ 6 ݆݇/݉݋݈ )? ∆ܶ ൌ 10 ܭ ൌ ሺ273 ܭሻ · 8.314 ܬ/ሺ݉݋݈ · ܭሻ 6 ݇ܬ/݉݋݈ · ݔ x = 0.0907 n W = 55.6 mol ݔ ൌ ݊ ாீ ݊ ாீ ൅ ݊ ݊ ாீ ݔ · ݊ 1 െ ݔ ൌ 5.97 ݉݋݈ ݉ ாீ ൌ ݊ ாீ · ܯ ாீ ൌ 370 ݃ Antifreeze needed: _____ 370 ________________ g b) (4 pts) From the included P xy diagram, i. Which line is the bubble point curve? 1 or 2 (circle one) ii. If we are designing a flash evaporator at 20 ° C, what would be the benzene compositions in the liquid and the gas at 35 mm Hg? x B = ____ 0.29 _______, y B =____ 0.55 _____ a) (4 pts) Consider a mixture of three condensable chemicals A, B, and C at 50 ° C and 2 atm. Under these conditions all three components are present in the liquid and vapor phase. A and B can be converted into each other, and the system is in equilibrium. Which parameters need to be specified to describe the system unambiguously? Explain your answer in 2 or 3 sentences. From the Gibbs Phase Rule: DOF = c - Π -r + 2 = 3 – 2 -1 + 2 = 2 Both temperature and pressure are specified so no other parameters can be specified according to the laws of thermodynamics.

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