Quiz 4 Solutions - ChE 230 Name Fall 2014 Quiz#4...

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Unformatted text preview: ChE 230 Name: Fall 2014 Quiz #4 Instructions For graders: — Closed book, closed notes — 20 min MC — Clearly state all assumptions, PROVIDE ALL ANSWERS IN BOXES l — Give all answers in the units requested with proper significant figures Multigle choice I“) Qts| — Circle the correct answer I. The heat of reaction for the following stoichiometric equation is: 2 3 B Fe203(5)+ 3 cm 9 2 Fee) + 3 (2%) Man = 211261033219 Circle ALL of the correct equations below. (There may be more than 1): A. 2Fe203(s) + 6 cs) 9 4 Pets) + 6 me) man = 21126102311239 1’3;- 2Fe203(s) + 6 C(5) —) 4 Fe(s) + 6 CO(g) A3311: = 422261031119 c. Fe203(s) + 3 as) a 2 MM 3 C0(g) Al’fi’xn = 2-11x105 [$1.9 41?; 2 Pets) + 3 COtg) a F6203(5) + 3 cm AfiExn = 4119610331219 2. Which method for solving energy balances with reaction always uses the elements as the reference state: a) the atomic balance method b) the extent of reaction method c) the heat of reaction method I d) the heat of formation method 3. The heat of formation ofliquid iron, Fe(l), is zero. a) True 13) False Problem 1. [10 pts] In the lab, you are tasked with determining the heat of reaction for the following stoichiometric equation: A + 2F —> C + SE The heats of reaction for three known reactions are shown below. A + 4B —> c + 2D Afian = —12.8 kJ/mol 3E —> 20 AHan = 22.3 kj/mol 23 —> F A1?an = —2s.6 kj/mol a) Using Hess’s Law, write out the combination of the 3 known reactions shown below and cancel terms to yield the reaction of interest. b) What is the heat of reaction for the given stoichiometric equation? 0) Is this reaction endothermic or exothermic? a) Show outside box " “'3’ _I_ I .a’ v rm- 3 Problem 2. [IO pts] Biodiesel is created by generating esters out of the fatty aid chains of triglycerides. In the reaction below, methanol is reacted with oleic acid. Using the information of the heats of formation, calculate the heat of formation of methyl oleate: A k C18H3402(l) + 3140(1)” (3191136020) + H200) AH;an z —11'34m—:1 oleic acid (C13H3402. 1) Ag}? : _764'8% *0 _ 11. methanol (CI-I40, I) AHf _ —238'6mal methyl oleate (C19H35021') A“)? = ‘ % water(H20, 1) A? = ‘285'84% Problem 3. [20 pts] The body removes extra nitrogen from protein metabolism in the form of urea present in urine. (This was the same material in the instant ice pack used in class. Thankfully, that urea was formed synthetically and not isolated from urine.) The heat of solution for urea is approximately 256.4 .l/g urea at infinite dilution and 25°C. Urine can contain as high as 30.00 g of urea per L of urine. The original isolation of urea from urine occurred in 1732 by Herman Boerhaave by evaporating urine. Assuming the urine is dilute enough that the heat of solution doesn’t change with the r value, how much energy is required to evaporate the water from 1 L (1000.0 grams of solution) of urine containing 30.00g of urea (final temp 100°C) in this open system? The urine starts at 250°C and boils at l00°C, and the heat capacity for liquid water is 4.184 J/gK and solid urea is 1.545 J/gK. The normal heat of vaporization of water is 2.257 kJ/g. a) What is the simplified energy balance? b) How much heat must be added to evaporate all of the water? Bonus — What object failed to work during the demonstration in front of the class? 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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