Quiz 3 Solutions - ChE 230 Name If 9” 1 “"4"5...

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Unformatted text preview: ChE 230 Name: If] 9” 1*) “"4 "5 Sect. # Fall 2014 Quiz #3 For graders: Instructions 1 — Closed book, closed notes — 20 min — Clearly state all assumptions, PROVIDE ALL ANSWERS IN BOXES — Give all answers in the units requested with proper significant figures 2 3 B . [15 pts.] lsopropyl alcohol is a main ingredient in many hand sanitizers. it feels cold when applied due to the heat that moves from the hands to the alcohol to warm and evaporate the liquid. 2.50 g of liquid isopropyl alcohol is warmed from 22°C to 37°C and then evaporates to form vapor at 37°C. In this problem, the energy balance simplifies to Q = AH since the only work is PV work. The standard heat of vaporization is AHV (822°C) = 732 J/g. Assume that the heat capacity for liquid and vapor are constant. prnquid = 2.68 J/g0K and prapm = LS4 J/g0K. a. Draw a hypothetical process path from the initial to final state utilizing the above A)?” value: ' b w s . I! A r: , 150 ro anol (li uid 22°C) 9 I ' «7mm 4 ‘ .7 f '1 .. -" Til: -—‘—* Js_,.m/i:wu‘i tau/7.x,» my”? 7" ’ t ’ "U p p q , jurflgk 3.. . . _. b. How much heat (in J) is transferred from the hands to the isopropyl alcohol in the above process? 2. [10 pts] Methanol is a common component of windshield wiper fluid. lf 1.25 mols ofliquid methanol is cooled from 35°C (next to the warm engine) to 20°C (on a cold Michigan windshield) at constant pressure (1.0 atm), calculate the heat term (in kl) for an energy balance on methanol. Is the sign positive or negative? The CD (with T in °C) is given by the following equation: Cp [k]/(mol-°C)] : 75.862410"3 + 16.83x10'5T 3. [25 pts] A humidifier boils water using an electrical heating element and functions as an open system (semi-batch process as I atm). The tank initially contains 2.3 kg of water at 25°C. Use the steam table found at the end of the quiz. a. Write the complete energy balance for an open system b. Simplify the energy balance for this problem 0. What is the PV work done during boiling? (Remember AH = AU + APV) c. If electricity costs 15 cents per kW-hr, what is the total cost to boil all the water in the tank? Wm’lt M'— —“—-—-—g)-—~ M mums) 11°C) P0201} w.“ s _—_— r Wu“ Slum Water Evapmatiun 51:01-11 70 0.3117 011nm I 72 03396 . 74 03696 “55 301" 2472 301.4 2329 2630 16 0.4019 01101025 ‘2” 3093 2414 3093 2323 2633 18 0.4365 0‘00 3'9” 3'32 2416 3132 2310 2636 - 1W8 3.619 326.4 2419 326.4 313 2639 :3 3233 0.001029 3.400 334.0 2432 334.9 1300 2643 a 05558 0.001030 3.161 343.2 2434 343.3 2.303 2646 86 06011 0.001002 2934 351.6 2401 351.1 2298 355” 88 . 0001033 2.121 360.0 2490 360.1 2293 2653 0.6495 0.001034 2536 368.4 2491 3605 2288 2655 3121 0.1011 0.001036 2.361 316.9 2493 311.0 2282 2659 0.1560 0.001031 2.200 385.3 2496 3115.4 2211 2662 94 0314s 0.001039 2.052 393.1 2499 393.8 2212 2666 96 0.8767 0.001040 1.915 409.1 2501 4022 2261 2669 90 0.9429 0.001042 1.789 410.6 2504 410.1 2262 2613 100 1.0131 0.001044 1.613 419.0 2501 419.1 2251 2616 102 1.0016 0.001045 1.566 421.1 2509 421.5 2251 2619 BONUS (all or nothing): What type of company did Prof. Thurber work as an intern? PLEASE READ AND SIGN THE FOLLOWING STATEMENT AFTER FINISHING THE QUIZ: I have neither given nor received aid on this quiz, nor have I concealed any violations of the honor code. Signature ...
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