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exam2sol - CHEMISTRY 204 Name_W Hour Exam 2 March 179 2010...

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Unformatted text preview: CHEMISTRY 204 Name __W Hour Exam 2 March 179 2010 Signature Prof, Jim Lisy This exam contains 30 questions of equal value on 9 numbered pages Check: now to make sure you have a complete exam You have two hours to complete the exam. Determine the best answer to each question and circle your answer on the exam“ Total (100 pts) "Useful information, formulae constants and a periodic chart of the elements are on the last page of the exam. You can remove it from the exam as you answer the questions. VERSION A Cl-llfiMlS'l‘R‘Y 204 Hour Exam 2 age No. 1 1. Consider the solid MA2 (Km 2 7 5x10”) where Ka(HA)=1‘00x10"13t Calculate the solubility ofMAg (s) in 1 O L of 5. QM ls ° 7g acid . ,1 1 _ , a 5. o M g , ,, Vic. 2.7xictM d. i.0x10*5M e» None of these Considering the following salts and their Ksp values, which salt will have the greatest molar solubility in l 0 L ofwaterV Ag2C032 81x1012 AgCl . 8.3x1010 ' ' AggS: homo“ AgBr: 7.7x10“13 Agl: same“ 3, Consider the following reaction; which. of the following is true? Phco3 (s) ea tab” + 0032" K51) 2 33x10"14 a, Adding more PbCOg will produce more sz+ and C032“ ions be Decreasing the temperature will produce more ions C: The reaction is exothermic The addition obe(.N03)2 will decrease the solubility of 13me e; The solubility will increase when the pH is increasedfi 4. What will happen when 4X10'5 M Pb(NOg)2 is mixed with ’7X10"2 M Nal? (KSp (Pblz) ~ 1.4x108) ,_ ,1 a. Nothing will happen 5': " T“ i " i‘ A precipitate will form c. There will be an explosion d. The solution will turn blue e. None of the above Cl-ffiMlSTRY 204 Spring .2010 Hour Exam 2 Page No. 2 5. Considering the following; solution of ions, Cum, Fe2+ , Mg2+ , and ZnZl". As the p11 is raised what is the order that the ions will precipitate 151nm first to last?w as, monk: 2.2x10"20 ” Ks, Fe(01—1)2: 1.6x10“14 Ksp Mg(Ol:l)2: 1 .2X10 KS, ZH(OH)22 1.811110%? Mg2+, Zn“, Fez: Cu2+ C112: Fe“, 2102+, Mg” 032+? Zn”, Fer”, Mg2+ , M g2+, Fe“, an+9 Cu2+ , Mg“, Z112: (3112+, F621 c. d: 6. What is the change in free energy of an unknown salt AZX that dissolves at 298K if the concentrations at equilibrium are [A+] = 2.31110”4 M and [X2] 3 1.521110"2 M? a 51.9 kJ/mol h. 31.2 lei/11101 c. 40.0 kJ/mol d, 10.0 kJ/mol e 430.0 kl/niol 7. 1.00 g of an unknown salt/118103 (MM=170g/1nol) was dissolved in 1.0L of water. Then 100. mL of this solution was then added to 100. inL of 5.011103 M solution of NaCl A solid was formed and extracted. htained solid weighed 0.070 ' What is the KS}, of the precipitated solid? ' " '1 " ' ‘ ‘ : :1 ;: f i z“\ _ '2 \g, a. 1.1931106 11. 2,38x10”7 c. 1,,21x10”9 d, 6.0311109 3001:1118 8 What volume ofO. 0848 M IlCl (aq) must he added to 88 8 niL of0 233 M Nagl’04 (aq) to ieach 111 st second and third stoichiometiic point? _, a. 32.0 mL, 64.1 mL, 96.1 mL h. 61.9mL,123.8n1L,185.7mL c. 112 mL, 225 mL, 337 mL dz 244 mL, 488 mL, 732 rnL “e”; 570 mL 1140 n1L, 1710 mL CHEMISTRY 2041 Spring 2010 Hour Exam 2 Page No. 3 9. Novocaine. which is used by dentists as a local anesthetic, is a weak base with pr r: 5.05. Blood has a pH of 7.4. What is the ratio of concentration ofnovocame to that of its conju ate acid in the bloodstream? . 0.0282 b. 0.0359 0. 0.0447 (1. 0.0794 e. 0.0816 10. At What point in this titration”, of ‘arséhié acld (H3ASO4) with base would one expect to find a mixture of primarily H2A304" and a lesser amount of HASOX”? (picture source: http://wps.prenha11.com/esm_mcmurry_chemistry_4/9/2408/616516.0w/indexhtrnl) WW WWWWMT '13 i (:1 an 1“+ MM 10 If , "E 9 ‘3 I % I? ./’Meyjfé;\ /“ {x B .x' a t n 5 _ C At 3 f 2 MM” % . t: \a [I] mWWwwtaw-wtwwmewwwtmwwmma (:3 LE] CD LIT) C3 L11“) (:3 kl? CD W m '“t E3 533 E53 53.: a hint. Eaee {mt} a. Point A. b. Point B. Point C. . Point D. Point E. .0 CHEMlS'lRY 204 Spring 2010 Hour Exam 2 Page No. 41 11 Which solution would come closest to making a pH 7 buffei? (Refeience data for phosphoric acid 1131904,: pKa1-w 2 2:; pKag -~ 7 2 pK33 412. 2) Q a solution of NaHZPQ4 a solution containing equal. amounts of NaHZPOzi and NagHP04 a solution containing equal amounts of £1an and NaHZPO4 a solution containing equal amounts of N32HPO4 and NagPO4 e. a solution of NaZHPO4 129’ 12. According to the table below which of the following indicators could you use '01 a . titration of O 20 M CHgCOOH (aq) with 0 20 M NaOH (aq)? (Kaw M l 8 X 10 ) ' i L a. Thymol blue b. Methyl orange c, Litmus Phenolphthalein J Alizarin W Indicator Thymol blue prIa pH range of color change 1.2 to 2.8 Methyl orange IIIIIII _ 3.2 to 4.41: Litmus ___ . 5.0 to 8.0 MPhenolphthalein . 8.2 to 10.0 11.0 to 12.4 13. Which of the following statements is correct? (a) The buffer capacity and its initial pH is dependent on the relative acid-base ratio and not the absolute concentration. (b) When a monoprotic weak acid is titrated with a strong base; the equivalence point is less than pH 7 " (c) An ideal pH indicator would have giadual change 1n color over a large 1ange of pH: (d) In a solution of phosphoric acid 1131304,, it is theoretically possible to have significant concentrations of both HzPO4. and P043 at the same time ate) None of the above. 141 To simulate blood conditions, a phosphate buffer system with a pH ‘“ -.7 40 1s desned. What mass ofNaZHPO4 must be added to O. 500 L of O. 10 M Nal—12P04 (aq) to prepare such a buffer? (pKal w 2 2 pKaz - 7. 2, pKag - l2. 2 and assume no change in volume) 11.0 g b. 28.3 g c. 31.2 g d. 57.7 g e. 80.1 g CHEMISTRY 204 Spring 2010 Hour Exam 2 Page No. 5 15) Calculate the pH Ufa 0.10 M solution ofHZSth. (Kaz r: 0 0:2) , _ 01 201 j ‘01"; 0.96 c) 0.89 d) 1.00 0) 1.05 8.0 - 9!»? g 610 K 2.0 « 0‘0 “gimw‘n ~—¢-—~ , rwwl,_‘4,1 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Equivalents OH" Adapted from: http://wwwbio.cmuggL/gourscs/03Z3 l/LecFQi/j..ccO4/HisTitr.9if Use the above plot off/16 titration oft; polyprotic acid, H314, for the following question. 16) What is tho value of pKag? a) 1.9 b) 4.0 (2)60 d.) 7.6 e) 9.2 17) Calculate the pH ofa 3.4 x 108 M solution 0mm. .0) 7.00 d) 7.47 0) 6.85 CHEMISTRY 204 Spring 2010 Hour Exam 2 Page No. 6 18) Choose the reaction below whose equilibrium constant would be denoted 1/ K32. __‘ _ -: 9 H MH3Aeq> + H200) ‘— H30+(aq) + HzA (aq) KO; HZ A A + H Mia—(aw H200) 7“ H30+<aq> + HPOfi—(aq) \ -- SO3(g) + H200) =H2304 (g) KC; '7: H 15? '2' + H 4 A fig/A" ;. H302”) + 30421aq) 3 HSOHaq) + H200) 7- HSO4'(aq) + H200) “-3 H30+(aq) + SO42'(aq) 19) Which of the following represents the expression for charge neutrality in a dilute solution of NaOH in water? a a) [N25] = [OH'] b) [Na+] = [H3o+] + 2[OH‘] [N5] = [H30+] + [OH'] [Na+] + [H301 = [OH'] e) [N6] + [OH'] = [Hm 20) Given the following reduction potentials: 1112+ + e' —+ In+ °= —0.40 V 1113+ + 2e' —> In+ E°= —o.44 V What is the reduction potential, E°, for In3+ + e" —> In2+ ? a.“ -0.04V b. 0.04V C.' n '0.4;AV ) Ag, 6 :5 4 :"d- -0-4§,\1? , 0 \’e’.""”0’."48V a;filflt4( #4 {#714 Aa6£ A L/~ ofl‘anW ]) (Yd-«ME: AL“ ”55’4“” 2 a 0 . :2f 3* f 7 A“ «m / , 1w +1; ‘“ 1” «an; 417(453 “3 j, 4 _7 1.5—va a £532: #6,} (+9.40) “ 7 7 7 / ”Mr/#7,; Z (flaw/43 * 0 ‘M>9 [/0 . ; M J J 7, :7 r ((U‘SQ ”0.:t‘éj wpaqsl? o [(12 5"" 3’ 2 CHEMISTRY 204 Spring 2010 Hour Exam 2 Page No. 7 ) fraction 14 Adapted from: http://www.chemueensu.ca/people/faculty/mombourguette/firstyrchem/acidbase/ImageZ86.gif 21) Using the composition diagram above, which illustrates the fractional compositions of ions present of a diprotic acid as a function of pH, what is the approximate value of K31? Qiéms PKG" ‘ L” c 7'1 OM : qu“ lQ’S d) 7.9x10'8 e) 3.2x10‘10 22) Mng is very soluble in water, while PbC12 has a Ksp=l .6 x 105. Which of the following statements is consistent with this observation? a) The magnitude of the lattice energy of Mng is greater than that of PbClz. K b) PbC12 is covalently bound. X c) AG°301 for MgClZ is positive. K d AS°501 for PbClz is negative. >< @ The magnitude of the hydration energy for Mg2+ is greater than that for Pb”. 23) Consider the following redox reaction: 3AS2S3 + 14 C103 + 361—120 —> 6H3ASO4 + 9 SO42— + 14 C1. + 18 H30+ +3 —7- +5” ' +4 H0 «t Identify all species being oxidized and reduced. s CI 2, redrmm . Oxidized: S; Reduced: C1, As 00 J ®Oxidizedz As, S; Reduced: Cl Cl +5, .27 C 1‘... Y‘C “Ce xidized: C1; Reduced: S / . M f 4 {86/ ”Oxidized: S; Reduced: 0 i515 Jr; v7 A9 +3 0% e) Ox1d1zed: As; Reduced C1 CHEMlSTRY 204 Spring 201.0 Hour Exam 2 Page No. 8 24. What statement is true about the following reaction? Cu(s) + 2 Ag+(aq) we Cu2+ + 2 Ag(s) a) Copper is being reduced b) """ ”Silver is the reducing agent “'"""'Copper is the oxidation agent gilver is being reduced 6) Silver is being oxidized 25. What is the value of Bowl] for a galvanic cell with Silver and copper half~cells? 2 Ag(s) + Cu“(aq) w} 2 Ag+(aq) + Cu(s) a) 0.46V L bl 1.14 V 9);? “0.46 V a) 4.26 V e) “1.14V 26. Which of the following ione is most easily reduced? at) CU“ (aq) b) 2112“” (aq) c) Fe2+ (aq) 91),, SfiZi‘WD 59) 'Agi' tag} .270 Calculate the equilibrium constant for the following reaction at 25°C Fez-(S) + Cle‘wq) <-> Fez’l‘wq) +- (36(3) ,aL K m 4.7 h) ";:K m 22.5 c) K. 3.11 d.) K m 0.2 e) K6113 CllEMlSTRY 204 Spring 2010 Hour Exam 2, A Page Not 9 28., A potential of 0.142 V is recorded under standard conditions at 25 0C for a voltaic cell constructed using the following reaction. Pbthaq) + 2 Cl"(aq) w> mow) Estimate (one significant figure) the solubility product, KS1), for PbClz. Refer to the following unbalanced equation for questions 29 and 30. (Xfinflwq) «t 2 M110; (aq) + (Y)H+ was» (Xfinlltaq) + 2 M112+(aq) + (Z) H20 29. In the above balanced equation the value fX is ...
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