Exam 2 Solutions

Exam 2 Solutions - Exam #2 Chemistry 112 Spring 2010 Name:...

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Unformatted text preview: Exam #2 Chemistry 112 Spring 2010 Name: V7 ff W‘gV Kg? Cg» Social Security Number: XXX-XX- Seat Number: For ALL pH questions, express the answer to 2 decimal pieces 1!! Write Neatly I?! Show all work 1!! 1) (50 points) Titration: This is a multimetep problem: Calculate the pH for the titration of 100 mL of a 0.1 M NH3 solution, K, = 1.8 x 10‘s, with 0.2 M HCl after: a) (10 points) 0 mL of HCI have been added b) (12 points) 30 mL of HCl have been added c) (16 points) 50 mL of HCl have been added (:1) (12 points) 70 mL of HCl. have been added K : f/VHQECQH‘Z a) 0 mL of HCl have been added H33 MH3 + H20 :2 My; + 3H I 0.( "- " C “K +>< '6')! ‘6 01.4 >4 V F '2. K :: ’6Xl0fz X b car—x .. z.{§><L07= .23., 0-1 .b) 30 mL of HCI have been added (WA/Miami”): 10mm! WM;= (0.2m>C?0mL):_ gmmoi 4430* W”: "l’ “3mg?- I/I/ank'i’ {42,0 l é, _, .. Mi «6 +é .——" ‘i‘ (9 g "M {>un 44, W .K : (>U0 QH: Vkfi "rig/"VI; Km 19 Ft K“, mm W LQXIO” ngft'flwflww? fka3q2§ c) 50 mL of HCI have been added :0 M Ma! Mm CO.Z>C§OWLB: {Okinawa ( {430+ CHME Wflfi H301“ WM? Hm § {0 [0 .w K «\0 r10 {(0 w"- i; 0 0 u? " I . lommo ': 0065”? M AWL/((1? 100+§0mlx WM + Hu? 441/3 + H30 “f M E 0.065? x f: wwa ~r>4 TV 5 905wa K x '1 K“ : §.56”><t510 ; K L fifiuwr X 45¢: 055? 0.065%4 .. ’2. Mg 1L 5§3><0m; *5 x; gig)ng H39 L W? E l d) 70 mL of HCI have been added 50 Wit/Viol . + (piK%mmD: r4wwwzwzfi (HM? fl/H3-6 4439+? fl/HQ—ff HLO ‘5" (0 14* “w ": war—1L0 “"10 “0 g ‘9 it 10 - ngow WMK odd/f Wm -—— Owly (/75 $144314? aid/(I Ha” .giflflEL w aazwyw +uo+ :99 4/710 [ML “ 3H: L43 2) (5 points) What is the pH of a 4 M Ba(OH)2 solution? “@302 NE W2 + 2W“ {Cf/M 2,954»: gm 3) (10 points) The pH of a 0.3 M pyridine (CEHSN) solution is 9.39. Calcuiate the Kb for pyridine. CgHgfi/%'Hmfl wi? Cgfifiwfifi¢~ééfia“ €21; a (13 W ‘W W ('3 w><1_ ' 4% K +% @ a9%~ fififi “w” M w PH; at??? {@HZ: X :: Zifyk’mf“? €f4%”4 flHT Wy'l “ kbzli I H]: .7“: W K:2.9M€i@j gcggj ' §3~x 4) (5 points) List the following species from most basic to most acidic. Circle the most acidic species. KC}, HNOS, Ba(OH)2, NH4C1, KF 840201 K? W Wmfif 5) (10 points) The Ka for hydrofluoric acid, HF, is 3.5 x 104. CalcuEate the pH of a 0.1 M NaF solution. W 6! l “M “go?” C wax; ii... “fjé El flaw-g )4 >4 2 64mm $53; M g; » >4: fllszérfafl wwgwwkflfl 7 if — W: 6% UH: €23 j 6) (8 points) Calculate the pH that results when the following solutions are mixed: 100 mL of 0.1 M formic acid (HCOOH) with 150 mL of 0.3 M sodium formate (HCOON a). Ka of formic acid is 1.8 x104. (“@00M7(@d1M§ 5-“ M woe/mew” :: Ma 650 MX'OBIM‘) if £95 WWW} 3:" Mb 34% v ii a. M w EH, 333/4” “vi/Mg. m #6:}??j 7) . (4 points) Calculate the volume of 0.5 M HCl needed to completely neutralize 100 mL of 0-2 M Sr(OH)2. H Mr M :1: 5: ME ME 0.Z>[ Wé) 5CD( V2 65 8. (8 points) For each pair, circle the one that is more acidic. Extra Credit: (5 points) How much water will you obtain if you react 2 g of hydrogen with 8 grams of oxygen? Henry’s Law: C : kP Roult’s Law: P solvent : Posolvent ° Xsolvenf: Boiling Point Elevation: ATE = kBm Freezing Point Depression: ATF = ka Osmotic Pressure: I1 = MRT 1320,0821 Loatm/moloK _R=8.314 }/m01°1< aA+bB'm cC+dD K 49M 6’9 "M‘Jaimb KerJRT)“ ’2 [H30"‘][OH’] m 1 x 10-14 2 kW pH + 1001—1 2 14 = pkw pH 2 ~10g[HgO+] [H301 : 10-pH pOH : ~10g[OH'] [OH] = 10'POH k 2 [H30+][A‘"] k : [BI-1+] [OH—1 a [HA] ‘0 [B] kak‘b m kw Pka + Pk 3 Pkw 11 pH: pka+logefif ...
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Exam 2 Solutions - Exam #2 Chemistry 112 Spring 2010 Name:...

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