Sol4 - Che 2150, Fall 2008 Problem Set 4 Due Friday, Sept....

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Unformatted text preview: Che 2150, Fall 2008 Problem Set 4 Due Friday, Sept. 26, 2:00 PM Nau- S; 0419 A 5 Student TA: Lab Day: Sugg sted Additional Problems— Ch 3: 31, 35, 37, 43, 47, 51, 59, 39, 35, 101, 119 l. .lculate [H30+], [OH‘] and pH for: The solution prepared by mixing 90.0 mL of 5.00 M HCl and 30.0 mL of 8.00 M HNO3. motes HCI: 0.0aocx $70025? ; 0.4mm]? md’KLS HM03= anSOLXEpDM; 0.2150644 (._. {1450*}: W; mm O.l‘LoL. PH: floidi-L [O‘H'lz mttaio" m. The solution prepared by dissolving 0.56g of benzoic acid (C6H5CO0H, KEl = 6.4 x 10‘s) in enough water to make 1.00 L of solution. Moles BA 2' .fl : CfSEthO'} IZ’LL‘HMJ ; _5_ HBA +HLoC-fi—-3__ HEEL-r36 fo’fif A =é-‘4x10 . x10 av __- m[m\ LLSXS’IIO") 2: X I: 1 “LR F {015; d2..qu a {0 j'.:-. 0 x: Sim/0‘55”! = [#300 Egg“ : air/047‘? pH: 3.2- ‘3 A 1.0 x 10'7 M solution of HCl. Hint: You need to consi r the H30+ resulting from the presence of HCl, as well as from the H30+ and OH' due to the autoionization of water: .._1 4— " ZHLOET Hsorqaiwm’ {my} towel“: =I-Cer0'1m “in...” ILOKIO'IH’C X Ci 0 n y al 0 1047 (I no we“) r it? _ [opf’JZ-Qigk‘fo 00/”? 1c 2 (.15 )c m"? 1 How many moles of formic acid HCOOH (Ka = 1.8 x 10“) is required to prepare 0.60L of solution having a pH of3.40? +_ _ P H =—3."-[ O H g o + HCO" 5. ,, A _. H C0001; HZ’ éfil 145’ (run ‘ fl £51303" 339‘“ y o 0 ’1‘ .3 a; gag/0.7 *398‘xm 393%!!! z: ' x— '7 3.98 no” 2,..‘1hm'Y . , “fl”... {Tim/0‘ L {ha-€15 Frva W 395’): 1’0"?) ; (a z {’35 w": )C’JHPKIU‘AP' HYF é'qrym—I?) 1 K ~3.‘73xla “ x: [.23xl0‘3 Chli 2150, Fall 2008 Problem Set 4 Due Friday, Sept. 26, 2:00 PM 2. .ptain Kirk, of the Starship Enterprise, has been told by his superiors that only a chemist can be trusted 1h the combination to the safe containing the dilithium crystals that power the ship. The combination the pH of solution A described below, followed by the pH of solution B. For example, if the pH of Iution A is 3.47, and that of solution B is 3.15, then the combination to the safe is 3—47—8-15. The cmist must find the combination using only the information below. All solutions are at 25°C. Solution A is a 0.100 M solution of the weak monoprotic acid HX. Solution B is a 0.0500 M solution of the salt NaX, where X is the same as in the monoprotic acid in solution A. For this NaX solution, [OH'] = 1.05 x 10" M. What is the combination to the safe? , ~“I F0!“ ‘He Serum-J solo ( 8) [Hsoflz'Lox—m“ “War/0‘7 '— ?.§Zx/O"V H pH : IO-OL X +H,o :3 HX +oa 3, 0-050 0 O “)c +2: +2: /”f 0050-76 /“ L Jim s Kb 0.0813"): x:[ou] floss/0’7 L -Y H K : Iogk/O ) h- gr X b 0 050 floss/r7 K = Lw Mi ; Sans/0*“ OH [<5 ZZJV/O—n + __ per HK—FHL fiséo +OH A. Os/OO-x 9“- HY XL ’9 {LC/o —3 xsll‘qlSaud'? =é73x/0 I”? If _, Ch: 2150, Fall 2008 Problem Set 4 Due Friday, Sept. 26, 2:00 PM 3. nu are working as a summer intern in the Miami CSI lab, and have been asked to devise a simple ethod for the determination of the purity of cocaine. After some thought, you decide to base the termination on pH, since cocaine is a weak base: C11H21O4N + H20 <=> C1qu2104NH+ + OH- Kb = ? The solubility of pure cocaine in water is 1.70g/L. A saturated solution of pure cocaine was found to have a pH 2 10.08. Calculate the value of Kb for cocaine. Molar Ma?) as: Coca-/\€ := 303.1 1/nrp ‘ I. _ j/L : off : "/0309 ECBCQJAC] ' H 30 3_l°}lhrf F 2 3 (1+ #ao -=* affine/f“ kiwi) SUM; 0 O #7 _ cH'flfoafl Chiral T/ZOx/O'y flask/ft? mom/x _ xi 2 [[CJ fl [ ’3 . “<9 1’ _,,(_ 55AM} SWflO - .» W = Z-L§x/O e vs; /0"3 1 A recent drug bust resulted in the seizure of 1.25 kg of cocaine. It is common for drug dealers to “cut” valuable cocaine by the addition of a cheap inert white powder, thereby increasing sales profits. In aqueous solution, the inert white powder has no effect on pH. You dissolve 0.120 g of the impure cocaine in 1.00 L of water. The pH of the solution was measured to be 9.37. What is the purity of the cocaine sample, in percent by mass? we: 01.3? :3 Pol-F=‘-f-(93 fowl: 2.2% rZOFSVW CrHsO «3‘ 09‘ 7‘ 0"!"— c, :2,s?.acm"’a7 Mr [ca] E U 5L1 *1 3qki0‘§ +23 YxZOJS 2.3‘fx/0 7ram)‘ C 5 ' ' ' ' «j { [36m [masters L 2 Prize/(Vs 139‘s!“ (2.31m: f; jam). H) ” a : 7. (Mic/0’1 KL: : ZLéXZO 6 A 2 [do]... 2.29mi) ML :5 7099010 5 [009‘ EC *ZBMCZO'S = ' x A 0 12.05 0 it Another sample‘bpsuspected cocaine was tes e0 the same method. The pH of a 1.70g2’L sample was found to be 1 1.25. Could this sample contain only cocaine and an inert white powder having no effect on pH? Explain briefly. Mo ‘H4 TS" h71lter ‘Hum fiat/“IL gr— 5, SAL/‘flle/ ) COCOK‘IAQ said-H‘OI‘I) ‘50 "dee. flu/5+ be anowr base preSeMi Chi: 2150, Fall 2008 Problem Set 4 Due Friday, Sept. 26, 2:00 PM 4. Calculate the concentration of CO3} in a 0.010M solution of CO; in water (H2C03). If all of the C03} in this solution comes from the ionization of HCO3', what percentage of the H3O+ in solution results from the ionization of HCOg'? u—t— cho3 + LILO a: H- O 'f’HCO‘s 3 0 mo ex 9‘ k #1: I (fix/0' 2-) A!“va 2:44 0'0'0 a ozd'r’c ANTHEM é £~/o’££;£n7& Fl C0; + Hero é #3041“ CO?" L]: fit” [0“! Liar/0'87 é.Ck/0’S‘;’7 7 [C0 3L3: LL83: [049,7 (é-Cr/fl'rwl (‘7) z 9/. yx/a""__/ <90 Ram 7—“ m S Clue/0’ «7 ,. : (Lat/0*? 977 F5 A'Sfume jCC alas/0’5 Wk/fl 0 -5k/0 7.: n Calculate the pH of a 1.00 M Oxalic acid H2C204 solution, and determine the equilibrium concentrations of the species H2C204, HC204', and C2031 Kai = 6.5 x 10'2 and K32 = 6.1 x 10'5. HgCLOv+HLO E; #30” “Cad? loo —)< X A L ,L _______/f_____._ :: éS'x/O (00 v: 511‘- G-S-x/O‘flfi' ace/042:0 [#304,]: 0'25” k: -083, (0": (tit/o" ‘r—‘z‘ffi-gffa‘i'i {,H-L 0. Chi? Z )L: 0.22.; [Hzczp‘azo'wsm * + 1+ co; + at) i Czar?” +630 g [ “2.0931015” L 0.22 , ,r 0.22/5“ , [Cathie]: WHO M “X +1: 1”” / no tag 2: A 0.2”“ K x) otlSNQ —;Q_/;r/a’f ...
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This note was uploaded on 09/27/2008 for the course CHEM 1732 taught by Professor Davis during the Fall '08 term at Cornell University (Engineering School).

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Sol4 - Che 2150, Fall 2008 Problem Set 4 Due Friday, Sept....

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