Download Past Exam 3 Practice Problems with Solutions - Chemical Engineering Thermodynamics | CHE 344 and more Exams Chemistry in PDF only on Docsity! 1 20 July 2001 CHE 344 Hour Exam 3 Practice Problems 1. For the T-xy diagram depicted above for an arbitrary binary system (for T in oC) answer the following questions: • Illustrate the locations of the liquid, vapor, and 2-phase regions; the T-x1 curve; the T-y1 curve • Estimate is the relative amount of liquid and vapor for a liquid-vapor mixture containing 20% of species 1, held at 60oC. What is the composition of the liquid and vapor phases? • What is the relative volatility, α12, of the system for all situations where a saturated liquid exists at 55oC? Suggest why you think these results are/are not consistent with the presence of an azeotrope. 2. A binary liquid solution of A and B of known composition is confined to a closed vessel. Initially, the activity coefficients of A and B were determined to be 1.00 and 7.00, respectively, via UNIFAC. The system's temperature is adjusted such that the activity coefficients of A and B are now calculated to be 4.48 and 2.11, respectively. Unfortunately, the experimenter forgot to record the composition of the mixture in her lab notebook. Can you calculate a value for the mole fraction of A? 3. An equimolar liquid solution of benzene, toluene, and ethylbenzene is de- pressurized isothermally at 75.0oC until the first bubble of vapor is produced. Find the pressure and composition of the bubble. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 50 55 60 65 70 T em pe ra tu re , d eg r C 68.427 52.966 T 273.15 K⋅− T 273.15 K⋅− 0.9855 10 4−× x 1 y 1, 2 4. For a pure substance held constant at its critical pressure, its fugacity is equal to 0.40 Pc. Isobaric heating results in a new fugacity of 0.5 Pc. What is the initial temperature, relative to its critical temperature? By what factor is the temperature increased during cooling? 5. 140 lbm of 15 wt% H2SO4 at 160 oF is mixed with 230 lbm of 80 wt% H2SO4 at 100oF, yielding 20,000 BTU of heat, which is removed from the system. Determine the final temperature. Assume atmospheric conditions throughout the process. 6. For the xy diagram depicted above (at constant pressure), a feed containing 50% species 1 is flash-vaporized so that 75% of the feed is vaporized. Use the diagram to determine the composition of the liquid and vapor phases. 0 0.5 1 0 0.5 1 0.985 5 10 4−× y 1 x 1 0.9855 10 4−× x 1
