Chem1C Sum01 FINAL EXAM (Great Test)

Chem1C Sum01 FINAL EXAM (Great Test) - / . CHEM 1C FIN AL...

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Unformatted text preview: / . CHEM 1C FIN AL EXAM Summer 2001 Do not open exam without instructor's permission. I. Write your name and ID# on the Scantron form. Only the Scantron will be collected for grading. Keep this copy of the exam to check your answers. 2. This is a closed book examination. You may use a calculator and a 3x5 note card. Programmable graphing calculators are NOT allowed. 3. The exam time is two hours. The exam is worth 200 points. There are 40 questions; each is worth 5 points. There are 14 pages, including a periodic table on the last page. 4. Record the correct answers on the Scantron form as you work. No additional time will be given at the end of the exam to record answers. No credit will be given if a question has more than one answer even though one of the answers may be correct. 5. Exam scores, final grades, and answer keys will be posted by noon Thursday, Aug 2, next to RH 261. You may pick up your scantron on Thurs, Aug 3, 12-2pm, or Friday, Aug 3, 9am-l2, in RH 325. All inquiries about final coumg grades or exams must be made before Aug! 6th. Exam scantrons will be discarded after August 6th. 6. Any student caught cheating on the exam or a regrade will receive an F grade for the course and a letter of explanation will be sent to their Dean. 1. FindKfor the reaction: N02(g) + 02 z: N0(g) + 03(g) Given: (1) 2 03(8) «=1 3 02(g) K1 VIC {‘ (2) 2 N02 (3) 1:! 2 N0 (8) + 02(3) @ ail; = (K2 / K01” M/ b) K=K1 IKz f__ V C) K=(K1’ Kflm T% r’ 2 ~. i/ d)K=(K1/K2) 30?, 2.1), ' /c g 2 e none of these 2 ) ,2 2r , J NU “ii-7 Jb I: m L if ‘ " 2. Given: H2(g) + 12(g) a 2 HI(g) Kp = 55 and AHmu = -10.6 k] at 425°C If a sealed flask contains 1.04 atm of hydrogen iodide, 0.130 atm of hydrogen, and 0.160 atm of iodine, which statement below is correct? a The system is at equilibrium. {1; f" he system is not at equilibrium and must produce more products. 4 The system is not at equilibrium and must produce more reactants. H’l 9‘ d) The system is not at equilibrium and the volume of the flask is needed to predict the direction of the reaction. e) None of the statements is correct. 907/ 0% / om‘é alcuiate the equilibrium constant (Kp) for the following reaction: 3 A(g) 12’ B(g) + 2 C(g). L flask was initially filled with 7.4 atm of pure A and after equilibrium was reached, the ial pressure of C was 3.6 atm. a) 2.9 b) 12 Ki) L c 330-31226 Cffia gm 2 6) none of these fl 2)? ‘7‘ UVBX " 3’ g—N—EH’T/ r _, .. 4. Given: Hg0(s) +{4I (aqy + H200) 1:» HgI42 (aq) + 20 (aq) \ _ 3 'ch of the followingchafiges will incnease the concentration f I ? Add KOH. A d a catalyst. c) crease the mass of Hg0(s). d) Add 6 M I-INO3. e) None of these.‘ A 5. quilibrium is reached in a chemical reaction when W e rates of the forward and reverse reactions are equal. . he concentrations of the reactants and products are equal. /9’J/ all chemical reactions stop. (1) a and b e) a and c 6. Calculate the pH of a 0.10 M solution of HCl. a) —13.00 0 b) 13.00 at C) 0.10 D {fl r-t f d —1.00 r. typo F [0 fi\( Y, >6 2_ LL... slo‘f/ 7. The pH of pure water at 0°C is 7.46. What is the value of Kw at 0°C? —14 a) 1.0 x 10 b) 1.5 x 10‘14 @12 x 10’15 d) 6.9 x 10‘8 e) none of these 8. How many of the following ions can act as both a nsted-Lowry acid and a Bronsted- Lowry base: HCO3_ H20 HZPEO4— 4 a) one 4 ' two 5) three d) four e) none of these 9. Which pair of substances below is an acid followed by its conjugate base? V a) NH3, NH4+ 2- _ K b) HPO4 , HZPOA Kc) pH3COOI/LLIH3COOH2‘L _ / 2_ W {€03} correct 10. What is the pH of a 0.050 M solution of ascorbic acid? Ascorbic acid is a diprotic acid. (Kal = 1.0 x 10‘5 and K212 = 5 x 10‘”) a) 1.32 7’ b) 3.15 fig / 3)) \ \_ ;/ jg, /\A e) none of these \ 04 \L \O 34"“ 11. A solution of 8.0 M benzoic acid (CGHSCOOH) is 0.28 % dissiociated. What is the Ka of benzoic acid? 12. The percent dissociation of aweak acid increases when additional solvent is added to the acid solution. 0' rue b) False a .4}: *1. i 12v?” - in 13. Given: 1 CN(a + m) figs) +"H2CO3(aq). If Kc< l,what is the strongest base in 18 system7M'” \‘5—w— ' a) HCN @HCO{ 0) CN— c1) H2C03 e) need values for Ka and/or Kb to answer question- 14. When dissolved in water to form a 0.10 M solution which of the following would give a solution with pH < 7 ? A, A VJ I. {I y; _ MT a) the potassium salt of a weak acid 146 I v‘ ' ’ b) the potassium salt of a strong acid rot/w} " U /‘- _ he ammonium salt of a strong acid 1 *7 A ~ «fit—4 /I - < "7 ) both b and c e) both a and b I‘ /. / r I J b 0.1 M HOBr 0.1M HOI @Ax10‘4 M J. d) 3.5 x 104 M 15. Which of the following will have the lowest pH? at) 0.1M HOCI - viii-.63». d) They are all strong acids and will have the same pH. 9‘73 ./' 16. A bbffer is to be prepared by adding sodium acetate to 1.0 M acetic acid. Which of the following will produce the most effectivebuffer? a) M NaCI-I3COO - - (,2 - fix ;' M H w ("I If 3 ble M NaCH3COO ' A , A .3 c) 0.10 M NaCH3COO { ' d) 0.30 M NaCH3COO 7" 7 - c “21.0 M NaCH coo r 3 a ‘ F. -’ .1) F ‘>./ Z a .‘2 lat? 'r‘ ' y i . . km; \‘f . ' i - 17. What is the hydronium ion concentration [H3O+] in a solution that is 0.20 M in sodium formate and 0.15 M in formic acid? Ka for formic acid is 1.8 x 10—4. D a / f a) 0.20 M H ( T b) 7.0x10_4M $5 I; . H Fm ,, g {.10} “'50) tl§'“>( e) 2.4x10_4M “s4 ’ . (of/{1 7 My; LA \tgqi X10- 18. Which of the following titration curves will show a distinct "buffer" region? a) The titration of a weak acid by a strong base. b) The titration of a weak base by a strong acid. ) The titration of a strong acid by a strong base. 63 a and b e) a, b, and c l fiThe solubility of Ni(OH)2 is 5.0 it ill-'5 grams per 100. mL of solution. What is the K5p? fa), I .9 10‘11 x . t JJfl-l‘ ILA :j. \A v/ —19 "“ b)1.6x10 --< \0 .0 b - ,/- c) 1.6x10’16 H, “11% d) 6.2)(10-l6 loo M e 621th-19 ) 0 /\0 M U K j ’\ 1 9%“)? ‘ 3;} Which of the following substances has the greatest solubility in water? PbCO3, Ksp = 7.4 x 10'14 b) Cu(OH)2, Ksp = 2.2 x 10“20 c) Al(OH)3, Ksp = 3.0 x 10‘34 d) Mg3(PO4)2, Ksp = 5.2 x 10'24 Calcium hydroxide precipitates until athe solution is saturated. yThe solution is unsaturated and no pnecipitate forms. c) * e concentration of calcium ions is Ireduced by the addition of the hydroxide ions. 'd) e must know Ksp for calcium nitrate to make meaningful predictions on this system. All the statements are incorrect. fit“ is”) 3 4 " ‘ .r' K"?,/‘a...’v / we : - ' 8 ’22. Consider a weak'aéid, HX. If a 0.10 M solution of HX has a pH of 5.83 at 25°C, what is Mr the acid‘s dissociation in water? "‘a) :oikJ I ) ; 4x7 .vaxggso. kJ V. _ j: .. _ (it. . , _ g; h J (D I JV .w. . .- . .Q ,.1 M/l@x\‘ ‘ J k “A '33?" {a /:)3/Which of the following is true for a System at equilibrium? C’univ > 0 fl . f I AS°univ<0 , V M, g. t, c) AS°sys = AS°surr ' '7 L g AS°sys = AS°surr = 0 q t I. AS°sys = —AS°surr ' 5 t3" ' 24. In which one of these pairs would the entropy of the first substance be greater than the entropy of the second? Assume P and Tare the same for each pair unless otherwise stated. a) 1 mole of H2(g)l:t 25°C; 1 mole ofgflg) at 50°C mole of C12(g) at 0.5 atm; 1 mol 0 C12(g) at 1 atm c) 1 mole of F2(g); ll/rhole 0f C12(g) L' d) 1 mole of 12(5); 1 mole of 12(g) 6) none of these 25. For which process would 43° be expected to be most positive? \ . , _ a) NH3(g) + HCl(g) ---> Ming) ' ’2, -—*—7 I t- I; @hlfidg) ---> 2§T52(g) I l i A... j. c) 2.N2(g) + 92(g) + 4H20(g) --—>§ 2NH4NO3(S) .. d) 02(5) + 2H2(_g) --—> 2H2O(g) ; ,3 P. J 4:... J 8) H200) ‘--> H20(S) J x 26. Given: C2H4(g) + 3 02(g) ———> 2 ¢02(g) + 2 H20(g). AHrxn = —1325 kJ If AH°f of C02 and H20 are —394 and 4.42 lemol respectively. What is AH°f of C2H4(g)? “a +53 lemol ? 53 kJ/rnol c) —689 lemol d) +689 kJ/mol e) —26 kJ/mol #‘gggfig32(2'553432-2:;242‘ .. $12.77, 27. The temperature at which the following process reaches equlibrium at 1.0 atm is the normal melting point for phosphoric acid: H3PCIJ4(S) 2 H3PO4(1). Use the following thermodynamic data at 298 Kto determine this temperature. /\ ? - ? i .. I + I 7 8 U Substance H3P04(s) H3PO4(1) 2—4" { ‘ ' ‘ ‘ AH°f(kJ/mol) —1284.4 -1271.7 [:3 . (71-7 AG°f (kl/moi) —1124.3 —1123.6 ‘ S° (J/mol-K) +1105 +1503 . 4, a. w 5-. ’«r a) 286K lid ‘6 «0 i b 305 K h d. S 15 K C 5 ,L ,I- rid, a. 347 K ’57 "i if Mi C“ " 7 a K e) none of these 28. Two crystalline forms of white phosphorus are known. Both contain P4 molecules but the molecules are packed in different ways. EAbove 277°C the alpha crystals form spontaneously. Below 277°C, the beta crystals form spdntaneously. Predict the signs of AH and AS for the reaction: P4 (alpha) ---> P4(beta) athelow 277°C. ht...;€4H;"3€4SS‘-"‘n at”; grit: g: r; g." \ Stan—AS \ - «x J (1) +AH, +AS [\ x I .w 10 29. Consider the figure below which shows AG° for a chemical process plotted against absolute temperature. Which one of the following statements is an incorrect conclusion based on the information in the diagram? a) AH° > 0. g b) AS° > 0. c The reaction is spontaneous if the temperature is high enough. @AS‘3 increases with temperature while AH" remains constant. e) There exists a certain temperature at which AH" = TAS°. T(Kelvin)' \." /\\ 30. A graph of In Kp versus l/T for a reaction gives a straight line with a slope equal to 1.4 x lOé-land an intercept of 14.51. What can be said about this reaction based on this data? The reaction is endothermic. ' \W--"/ The reaction is exothermic. n 111. The reaction is spontaneous at all temperatures. ./ I a) I only b) II only 0) HI only (1) I and III e) Iliand III 31. What is the reducing agent in the reaction: 5. @2072" + 61“ 14 H+ .2 203* +312 +7 H20 , . I— l c) H+ d) Cr3+ I 11 32. Given: Au3+(aq) + 36 a: Au(s) E°=+1.50V “a 2 V 13‘ Cr3+(aq) + 3e‘ 1:». Cr(s) E°=—0.74V Which of the substances below is the easiest to oxidize? a) Au3+ (aq) b) A11(s) c) 03" (aq) d) Cr(s) fi 33. When a galvanic (or voltaic) cell is «treated from the Au and Cr half cells (in the problem "(2* above), the fl(Au, Cr) electrode will decrease in mass and Cl_ ions from the KCl salt bridge will migrate to the half cell containing (Au3+, Cr3+) ions. a) Au, Au3+ b) Au, Cr3+ (1) Cr, Au3+ II f it. .‘ A» ‘ SELjthat is Elie correct ling: notation describing a galvanic cell for the problem above? a) Cr(s) I’ Cr. (aq) If Au (aq) I‘ Ants)E b) Pt(s) I’ Cr(s) I Cr3+ (aq) ll Au3+ (aq) Au(s) I' Pt(s) c) fins) I Cr(s) , Cr3+ (aq) II Au3+ (aq) 3. Au(s) I Pt(s) d) Au(s) I Au3+ (aq) II Cr3+ (aq) I Cr(si e) Pt(s) I Au(s) I Au3+ (aq) II Cr3+ (aq)iI Cr(s) {Pt(s) ‘ I 12 35. Which one of the following stateme ts is TRUE? a) In a voltaic cell, the anode is negativ relative to the cathode. b) Oxidation occurs at the anode in both the voltaic and electrolytic cell. /{'An electrolytic cell utilizes a spontan ous redox reaction. ,an and b only Le) a, b and c are true. ; 36. A concentration cell consists of two iAl / Al3+ half-cells. The electrolyte in compartment A is 0.050 M A1(NO3)3 and in compartment B is 1.25 M A1(NO3)3. What is the voltage of the cell /_at259€?;1he\cell potential for A13+ +3e‘——> Al is —1.66 v. 6140- 0.083V .- b) 0.062V »- I.) c) 0.041v / d) 0.028 V v- e) none of these ,- 37. A "secondary" battery is aha non—rechargeable battery. b) ‘a rechargeable battery. c) the second battery in a series. d) a fuel cell. e) none of these. 3 fl 13 38. A current of 300. amps flows at an electrode where the reaction occurring is: + ._ Mn2+(aq) + 211200) —--> Mn02(s) + 4H +2 e How many kilograms of Mn02 are deposited at the electrode at the end of 24.0 hours? a/L 2.92 kg (bl/15.85 kg E) 11.7kg {II} .7 d) 23.4 kg \ a 1.. e) none of these “ ‘ t . La ,2 J . , c, I Ir -\ ’1 _| W i v 2 [In K H ' ” ht) } l I;- j ,p JV! .2) 39. An unknown metal (M) is electrolyzed. It took 74.1 seconds for a current of 2.00 amperes to plate 0.107 grams of the metal from a soilution containing M(NO3)3. What is the metal? (a) La $1 1 7W '.' .3; 22.3139 w e) Rh“ 1"} " 5 v \, f .// .‘l . . .. ‘ Qael‘og'r'lpig , 3) ‘4’ ‘ I; 9% reaction. Which of the following is not orrect? a) In K = (—AH°/R)(1fT)+ (AS°IR) ci b) ln K = —AG°/RT e i c) log K = nE°/0.0592 C. d) K = kfwd I krev C. ' eT'Ngll of the above are correct 40. During this quarter we have learnedLseveral ways to calculate the equilibrium constant for a ,_..._ a ...
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Chem1C Sum01 FINAL EXAM (Great Test) - / . CHEM 1C FIN AL...

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