Ex-3-3530-S11-soln

Ex-3-3530-S11-soln - CHEM 3530 - Exam 3 - April 1, 2011...

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Unformatted text preview: CHEM 3530 - Exam 3 - April 1, 2011 Constants and Conversion Factors NA = 6.02x1o23 mor1 R = 8.31 J/mol-K = 8.31 kPa-Umol-K 1 bar = 100 kPa 1 kPa = 7.50 torr 1 J = 1 kPa-L Molar Masses CH30H - 32. H20 - 18. C10H3 - 128. _ 2 _ N°t°= 'f axz+bx+c=oj then x =fi2iw/__4E a CHEM 3530 - Exam 3 — April 1, 2011 Name £35m .g (54) PART I. MULTIPLE CHOICE (Circle the ONE correct answer) 1. To approximately what volume must 171 grams of sucrose, C12H22011, be diluted to prepare a 0.75 Molar solution of aqueous sucrose. (A) 240 mL (B) 375 mL @ (D) 1500 mL For #2 - #3: When 16 grams of methanol, CH30H, is added to 108 grams of water, the density of the solution is 0.90 glmL. 2. The mole fraction of methanol in the above solution is: (A) 0.032 (B) 0.146 (C) 0.083 3. The Molarity of methanol in the above solution is: (B) 4.17 M (C) 4.48 M (D) 4.63 M 4. 100 mL of an aqueous sucrose solution contains 0.50 grams of sucrose, G12H22911. What is the esmetie ressure ef the selutien at 59 °C, in bar? (A) 0.04 bar (B) 039 bar (C) 6.1 bar (D) 39.2 bar 5. When 25 grams of napthalene, CmHs, are placed in 600 grams of CCl4 (Kf = 30 °Clm, Tf° = -23 °C), the freezing point of the solution is approximately: (A) -9.860 (B) 24.650 (C) -13.2 6c 6. When 41 grams of the strong electrolyte, Na3P04, is dissolved in 120 grams of water (Kb = 0.5 °Clm), the boiling point of the solution is (A) 958°C (C) 101.0 °c (D) 103.1 °c 7. The weak electrolyte, A28, dissociates according to the equilibrium, AzB :2 2 A+ + B'. When 0.25 moles of A32 are dissolved in 100 grams of H20 (K.) = 0.5 °Clm), A32 is 60% dissociated. The boiling point of the solution is: (A) 101.75 °c (B) 102.00 °c (D) 103.75 °c 8. When a solution of an unknown compound is prepared by putting 10 grams of an unknown compound into 500 mL of solution, the osmotic pressure of the solution is 1.0 bar at 25 °C. The Molar Mass of the unknown compound is approximately A) 500 glmo (B) 5,000 g/mol (C) 250 glmol (D) 50,000 g/mol 9. Which of the following pairs of solutions are isotonic with each other? (A) 1.5 M CaClz and 1.0 M KBr B _. s - u - and 1.0M KBr (C) 0.5 M CaClz and 1.0 M KBr I 0. M CaClz and 0.75 M K) 10. A 0.5 M solution of the dissociated sodium salt of a polymer, Na+P', is placed in the left compartment, 0.3 M NaCl is placed in the right compartment, and the compartments are in contact through a semipermeable membrane, which permits diffusion of Na" and Cl‘, but not P'. In order to reach equilibrium. (A) Na+ will move from left to right and Cl‘ will move from right to left. (B) Na+ will move from right to left and Cl' will move from left to right. (C Boh Na+ an l'il move from left to right. ) Both n Cl‘will 0 le. For #11 - #14: Consider the gas phase equilibrium, 4N02(g) + 02(9) ‘2 2N205(g). The enthalpy change for this reaction is -340 kJ, and the equilibrium constant is K = 8 at 175 °C. 11. For the above reaction, if the volume of the container is decreased, (A) the equilibrium will move to the left and K will decrease (B) the equilibrium will move to the right and K will increase C the equilibrium will move to the le I and K will remain constant .- ---o-" move ote‘ " ‘ ‘ ll 4 ‘ a Dr 1P5"' i 12. For the above reaction, if H2(Q) is addetl to the container at constant total pressure, l (A) the equilibrium will move to the left) and K will decrease (B) the equilibrium l ove to the right ad K II increase 'brium will move to the e - n Kwill remain on (D) the equilibrium will move to the right and K will remain costant 13. For’the above reaction, if the temperature is increased, I: p. - r r ‘ g N ‘Vfis (B) the equilibrium will moe to the right and K wil In ase (C) the equilibrium will move to the left and K will remain constant (D) the equilibrium will move to the right and K will remain constant 14. What is K for the reaction, N205 : 2N02(g) + 1/202(g) at 175 °C. (A) 0.25 (C) 2.8 (D) 4.0 15. The gas phase molecule, A, dissociates according to the equilibrium, A(g) \——‘ 8(9) + 2 0(9). The equilibrium constant is 1x10'3. If one puts an initial pressure of 3 bar of A into a flask, what is the pressure of C at equilibrium? [NOTE: You may assume that very little A dissociates] rs 0.18 bar (B) 009 bar (C) 0.14 bar (D) 0.03 bar 16. A hypothetical biochemical reaction is written as: A(aq) ) : B(eq) + 2H+(aq). The Gibbs energy difference using the Physical Chemists’ Standard State is AG°= +25 kJ. What is the Gibbs energy difference, AG°’, for this reaction using the Biochemists’ (or Biological) Standard State? ' (A) +105 kJ (B) +65 kJ (C) -15kJ 17. In the first step in the glycolysis cycle, a phosphate group is added to glucose (GLU) to give (GSP). The net reaction for this step is: GLU + Pi + ATP —> G6P + ADP AG°' = —16.7 kJ This is an example of a step driven by: r (A) Tandem Reactions = o o. -- ,o- (C) PhysiologicalConcentrations (D) Biological Standard State driven reaction 18. Which of the following statements is/are true concerning the binding of 02 to Myoglobin (Mb) and Hemoglobin (Hb)? X (i) Hb molecules consist of a hexamer of six Mb—like molecules /(ii) In muscle tissue after exercise (in which the 02 has dropped to 20 torr), Mb retains most of its bound 02, but Hb has depleted its 02 reserve l/(iii) The curve of 02 saturation vs. P02 in Hb is sigmoidal because the first bound 02 makes it easier for additional 02 molecu - to bind to Hb (A) i and ii (B) i and iii m (D) iii only PART II. PROBLEMS (Show work for partial credit) There are three (3) problems on following pages Problem 1': MAM" )3, L . 0.20 -------- -~:- -------- --------- -~:— -------- -------- -- I As we learned in class, the average humber E of ligands bound to a protein, R, is related to the ligand concentration, [L], by: 03° R = ..................................................... a. K +[L] 1 IR where n is the maximum number of bound 0 14 ligands and K is the dissociation constant. ' / ,, l4 J. + ,4» 0.12 -------- ------- " """ R 77 g L] Vi = = = s s l 2 2 2 i . i4 7’ 5 7/ ” 0.0 2.0 4.0 6.0 3.0 10.0 "2/ h < WK V" N n 1I[Ll (M4) (10) 1. A series of equilibrium dialysis experiments yielded the Double Reciprocal plot (1IR vs. 1/[L]) given above. Determine the slope and intercept of this plot, and from that, determine n and K 5‘ 2 {Li 9 “Ml ‘é’nfi z: 4/K AX /¢.¢n"-§g em" fl’fl/gg’m 7.4%; (26) 2. For the gas phase equilibrium dissociation reaction, N204 : 2 N02(g), the equilibrium constant is K = 3.0 at 75 °C. The enthalpy change for this reaction is A,H° = +57 kJ. (10) (a) If one starts with pure NzO4(g) at an initial pressure of 5. bar , what is the pressure of NOz(g) [in bar] after the reaction has reached equilibrium. NOTE: You cannot assume that only a small amount of N204(g) dissociates. )— l p .. raft/Zea 5 5 /,{0 a 75%;; 2% * A ' PS»: / 4 (06) (b) What is ArG for this reaction at 59 °C when Psz = 0.3 bar and PNoz = 4.5 bar? )1. 4&2» Qgééaré Q 3 «RV/Mk fimTéfg-k] 3. 3W <36»; '9? (3%?3/W5‘éé l- azlgéffl/vgf/éfi 5.3 -3 y ‘-‘ “31W” 1‘ +413. xm r ‘9 93/??1"; l1} 2. (Cont’d.) For the gas phase equilibrium dissociation reaction, N204 :2 2 N02(g), the equilibrium constant is K = 3.0 at 75 °C. The enthalpy change for this reaction is A,H° = +57. kJ. (10) c) At what t7mperature, in °C, is the equilibrium constant equal to K = 25. ? “ Mam; "if #1] 4w 2 tam/f? g _ V f 5, A V / f3>fé$§¥itéw I l— gk ’ / "' 'e "i ’w,é\ 1/ k “u ii 7% // <Qéét 'Kg 5" l i “a 9" 7; 3; 5“ , , ; .fi r2 k%/> ~ ‘ 5‘ _.— W‘ 2““ r " »’< t: w i, , #7 “new If ‘ I w we" ‘ r n—K‘ r a . we... seem Seal??? 3 f s «3 ~/ w er/é‘g/i é (10) 3. Two solutions are placed in contact through a semipermeable membrane. The initial concentrations of the two solutions are: Solution A: 0.40 M P+Br' [dissociated bromide salt of a protein] Solution B: 0.60 M KBr Calculate the equilibrium concentrations of K+ and Br‘ in both solutions. ' ...
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Ex-3-3530-S11-soln - CHEM 3530 - Exam 3 - April 1, 2011...

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