exam2 spring 2018.pdf

# exam2 spring 2018.pdf - Calculator and Instructor Provided...

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Unformatted text preview: Calculator and Instructor Provided Equations and Thermodynamic Data Only. Name: 60/ 90 "‘ BMEN 3315 Spring 2018 Exam 2. Question 1. (10 pts). You must prepare a test electrolyte with a carbonate buffer having a physi logical pH (pH=7.4). To maintain a pH of 7.4 at 37°C, dissolved in the electrolyte. What pressure of C02 gas sh to maintain the required pH? it is necessary to have a concentration of; 1.57 m ' 9f C02 ould be in equilibrium with the test'électrolyte '3 : Z.l7)xl0 Page 1 of 8 Calculator and Instructor Provided Equations and Thermodynamic Data Only. Question 2 (10 pts) Under biochemical standard state conditions at 298 K, the oxygen reduction half—cell reaction and potential are as follows: 02 + 4H+ + 43“>2H20 E°’ =O.815V In a test electrolyte at 298 K, in equilibriummith oxygen gas at a pressure of 1 bar, you measure a reduction half-cellBotential of +0.750 V. W at is the fugacity coefficient for oxygen in the test _ ,.___._......__._....—i. . Electrolyte? ~ :1 E = E“- RT ‘WQ Q = [“101 r- 1 a» V [Pat] [M E : 0 8r —. (8 “‘5 (2C1? \. {m ._____———1—-——--" (‘HWBQ [WK W1 (q {7 Qt‘uh\ l ‘ V I Hun-ammo] / . , 7‘72) 0., 75 in"; y: 1’ + W X“ y‘7b\n a H l‘ ’70-‘90 L' :13 Page 2 of 8 Calculator and Instructor Provided Equations and Thermodynamic Data Only. Question 3 (5 pts). Consider the phase-equilibrium diagram for a single substance shown below. pressure Pry/9Cf/L “:7 r? " 3 temperature What phases are present at point 1 l ( (7/) How many degrees of freedom at point How many phases are present at point 2 (on line segment AB) 2— How many degrees of freedom at point 2 I How many phases are present at pomt 3 :; How many degrees of freedom at point 3 ﬂ What line segment (AB, BC, BD) represents a vapor-liquid phase equilibria l5 { For a constant pressure increase in temperature, which line segment (AB, BC, BD) represents sublimation A (5 Question 4. (15 pts). You are maintaining calls in 50 ml of a culture medium at 37°C. You add 0.05 g of glucose to the medium and notice the cells change size. You suspect osmotic pressure. What is the change in osmotic pressure associated witl-Lthe addition of the glucose and did you observe the cells to shrink or expand? Be sure to indicate the u its for the osmotic pressure. (MW glucose = 180 g/mol, you can assume that glucose does not pass through the cell membrane). a; (mi x ,_' weir}, : 3.8m) M \QDOJ/ML BOWL infer C'C/f/l 6th,:ng {Ach/Je/ Calculator and Instructor Provided Equations and Thermodynamic Data Only. Question 5 (15 pts). Calculate the molarities of two solutions, one of NazHPO4 and one of NaH2P04, if 100 ml of each solution are combined to prepare a buffer with a pH of 7.4 having an overall phosphate concentration of 0.05 M. The pKa values for the phosphoric acid (H3PO4) equilibria can be taken as pKal=2.16, pK32=7.21, and pK33=12.32. Fag/M30? pic; 72/ ml: pic , A CW] [WI LH’PDLl’V] L ”(9042‘ _; 0.63 77> NQHzIDOl—f 30.01% Page 4 of 8 Calculator and Instructor Provided Equations and Thermodynamic Data Only. ____________________________—————— Question 6. (10 pts). The reduction of dehydroascorbate under biochemical standard state conditions is, dehydroascorbate + 2H+ + Ze‘ => ascorbate E°' = +0.08 V Calculate the potential E for the half-cell reaction at pH=S if all other conditions remain at the biochemical standard state with a temperature of 298 K. Page 5 of 8 Calculator and Instructor Provided Equations and Thermodynamic Data Only. Question 7 (15 pts). An autoclave is used to sterilize surgical instruments by heatin ater der pressure to obtain a temperature above the standard boiling point. If a sterilization temperature of 135°C is required, what is the pressure inside the autoclave? Assume AvapH° is independent of temperature and pressure and has a value of 43 kJ/mole? 1’- 100+Z730C 7 37519 i I Page 6 of 8 T; ’r 6800* 275 ._. M0\$ Calculator and Instructor Provided Equations and Thermodynamic Data Only. __—___—___—___—_l—____—————————-———————-—— Question 8. (20 pts) Tinoco Problem 3, Page pH. It is a powerful antioxidant, which scave a single-electron oxidation to the monod reaction: Ase => MDHA‘ + H+ + e' Ascorbate also undergoes a two-electron oxi Asc‘=> DHA + H+ Ze‘ 260. Ascorbic acid (Asc: vitamin C) is a monoanion at neutral nges free radicals. At a temperature of 310 K, it is oxidized in ehydroascorbate radical anion (MDHA‘) according to the E°' = +0330 V idation to dehydroascorbate (DHA): E°' = +0.08 V Finally, MDHA- undergoes the following reaction (called a disproportionation reaction): 2 MDHA‘ + H+ => DHA + Asc' a. (10 pts) Determine the biochemical st reaction? andard state free-energy AG°' for the disproportionation "MDHA My? 75%] 205,0.27747 W%77DHA+ Z/W‘DHA’J/H’f 7 AA: 3 we? *16/ Edgapé A éo’prﬂlA go”: ,0/35 6/, ; 4K 74M 90x — 0-15 ; ugiigj Page 7 of 8 Calculator and Instructor Provided Equations and Thermodynamic Data Only. b. (5 pts) What is the equilibrium coefficient for the disproportionation reaction under biological standard state conditions? A/G ; A/GOJ’ g—F’Q‘” Q‘ W 75 Wyoming % 16(5- ’ G: (3 (LT ’Agi’U/J -zu-k ‘ 3") a: (3 4: x (1, 7 Z 4471 to; c. (5 pts) What is the reaction potential E,’ fdar the disprop rtionation reaction at 10 K under biochemical standard state conditions if [Ast'] = 0.001 rnmol, [DHA] = 0.001 mmo and [MDHA‘] = 1 mmol. At these concentrations is the reaction spontaneous or not spontaneous? 8/; 59/ ’EL ,OmQ ”V3? 6 M ,6 , 0x MLQHA] 2: l0 ((0 ¢ " a: ‘ / maid w a ” 1x %7700 xozv/s’ -oazaa £49 3410‘ 7 # A(é \$0 77M elod’wlameapc Page 8 of 8 ...
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