10_CHM_31_Summer_Exam_2_Answers

10_CHM_31_Summer_Exam_2_Answers - Name; K5 V CHM 31 Second...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 8
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Name; K5 V CHM 31 Second Hour Exam, Summer 2010 General instructions: Please label each page with your name. Read the instructions for each problem! Show your work in sufficient detail to demonstrate your mastery of the subject, but be brief if possible. Work those problems you know first, and then move on to those you are not certain about. Please note each problem has the number of points in parentheses; the entire exam consists of 120 points on 8 pages total (including this cover page). Time limit =1 60 minutes. If you must use the back of a page, please indicate clearly the flow of your work (label the problem number). The last problem is multiple choice problems, which are graded only on the basis of the circled letter, although many of these problems may require calculations. This cover page may be torn off the exam, but please make sure your name is on the remainder. R=8.3l451J/(K*mol) m 0.08206L*atm/K*mol 1L*A‘tm W 101.32] 4.184 I / K. * g = specific heat capacity of liquid water ( H200) ) 5’ (2' Mr?“ my : Mag) + £an :3 @0974} W Name: E CHIVI 31 Second Hour Exam, Summer 2010 1. (20) The following parts are not related. A. Briefly define each of the following terms or concepts (an equation may help if appropriate): i. Le Chatlier’sprinciple— j 5‘ij ,4)?“ 5:51 Wag/WWW WALL xii/Ff 7W GWW5?@/€ W/f/Vé/éi? efflfigf’g ii. Buffercapacity—j’MVW/VV 67F {fig} VA] #1 we” 4% MW Woe-W MW Mr ‘7 Hf“ 7” iii. Relationship between [magi and [OH'(aq)] m gay W as? / +fl27rfly KW Kw: f/féflfflflflgfl M ,M aflflfle MW iv- chasm WW“ #71 flail/M7077??? MM Wflfl 2-3 wow/WWW 477%? M” a? WWW 4%: V. Lewis acid and bases, with an example of E33312: ,' a “f0 M We?! 6 Pf/fl Mme. owe/55%;, 5;; w“ 1%???) Vi. Reaction quotient (Q) m /,6/ W We 73 Maw/M WWW (7,5 WW 46;» fleas? B. For a particular monoprotic weak acid with an initial concentration of0.15 M, the percent dissociation is 1.8 %. Find both the Ka value and the pH. [0529: Cary/K ' "(’3 flail) 7"2frgfl) [W magic/m) 5’ MOB?“ W) “é/O/llr" 6/? “(m/(76W?) all 2:5 7 53%] r 22%)] r: » WW [MWJW war: aft/7 a : [waif ,7 3 (,flaaflflmfl in: [4% [MWJ lng X/d) w Name: l __ CHM 31 Second Hour Exam, Summer 2010 2. (20) A. Calculate the molar solubility of Ag2CrO4(s). For AggCrO4(s), the molar mass is 333.734 g/mole and K31, =' 1.8 x 10'”. w: ‘l’ . “/ 457803646) “Mama mayo/23> fly 3 WW 3 J: ..._.. c +32% H’ 6“ 24/ X + Z _ 2 5.. 24/ :WMJ [Mt/233)] r (W) (Jr) 3/43/43 33% 4/: 35579060 3-H WMWMW" v—s‘ X cram mam/2y ~,:- 3.5; X/y g1 ) ._,___. . ___,_..i,___.__,,...._..—«._,.,r. B. Calculate the solubility of AgZCrO4(S) (in mol/L) in the presence of NHMaq) that is at a fixed concentration of 0.10 M (Le. [NIl3(aq)] = 0.10 M always). For the complexion Ag(NH3)2+(aq), Kf 2 1.7 X 10+7 (Hint: use the definitions of KSp and Kf (and their equilibrium values) for these two reactions to generate a 3rd reaction that describes the chemistry that actually occurs). - #2301543) P”) 053% +35%) fly elf/WE 21%;” 7L 8 WW) Fa flaw/g? 3%?) fl; :[fiM/W) a...» ' l" - w E 43 a. ‘f’ 2 flfifi) cr- Z/%[/l/ 67W) “(KI/fl / § 5 """ 2: 55,0 WW6 , +21 Mr 3/” +34” X . a #42? I; f 2m 5. 3; f8, 57 mm?! x: 3 W) at) (My M == WWW M WWW/W c E Name: Q‘ CHM 31 Second Hour Exam, Summer 2010 3. (30) An aqueous solution of chloroacetic acid ( CICHZCOOHW) ) is often employed when a weak acid that is stronger than acetic acid is required, as it has a single Ka value of 1.3 X 103. An ambitious chemist performed a titration with strong base as the titrant to confirm the concenn‘ation of a 50.0 m}; chloracetic acid solution. A. Find the pH ofthe 50.0 mL solution of ClCHgCOOI-IWD if the initial concentration ( ]0 ) m 0.10 B. If the NaOHmD (the titrant) concentration is 0.25 M, What is the pH when 15.0 mL of NaOHm) have been added to the 50.0 mL of 0. 10 M chloroacetic acid solution? C. On the next page, draw a reasonable representation of this titration curve. The Eli/:5; graph is 28 squares tall, and 25 squares wide. 6%” D. Pick one visual indicator and explain Why it is the best one from the following list for this titration (the pKa of each u ' iven in parentheses): thymol blue (pKa = I4 I H/Ioia) 7L ' h w a [Jam 3 “E 3,: “" ' “W ee/ 5 rid—"X as: WW4?” .7 .4. a? “fit/W .. r» we: memo fiflifiWW/ffl/w’fl’ i «Time/fl M “[flfeflj fflsmtflepfl/zggfl .2.- ewflflew ) s: /, i 7 8, HIV, Effie/til (/2 f7: :3 ’ (es/flMMflWi/éj 3%,” ML (aw/w) M I W “4 “" a. («R7 ' __ WW ave/7(a) «AW, H/aflm x577; vfjflfiff,q .. MW We”, i W M; WW; We) M77 4;; :9 2% did/55% ‘ wffi’ “31,77 4 we W WW M . WW: Wile/fl w 11/,Z7‘W’fi Male-7 WM fisaWWd/V Mesa/V) Ar 44/, Name. CHIM 31 Second Hour Exam, Summer 2010 Z 0 W; 677:: CHM 31 Second Hour Exam, Summer 2020 4. (22) A. Citric acid (denoted by chit(aq) for the fully protonated form) is a tri-protic acid found in citrus fruits with the following values: pKa; : pKal m pKag, = Examine these values, then list the pH range(s) over which citric acid would be suitable buffer. Answer here: M)» . ..._ WW; Mitt 2134.13 + 3376?” 4’ WM” ‘7‘? 3‘8 7’ (f7 » B. A buffer is composed of 0.15 moles of the fully protonated citric acid plus 0.045 moles of NaOH(aq) in 500.0 mL of 3200). What is the pH of this buffer? (9.6%“ Mega: N’ WWW; Mer W7? #3 0/75?) W W”? Wit/Wife) 2:) [Hgolfimj z: W/(jM/fflé “magma :3» m/é’g/M/lflfwfi “WE/i"? f Hay/6123)] : miayj’gm eWM swim“ may M) - _ fig/017m, ): 3J3 70W: fflz/oflfllvhdfl54mtxwgmj W}: L. .. W L: Gag/“(i 415W lad/7’ WV ' :9; MM a? 6%? Mae/5 C. An additional 0.20 moles of solid NaOH(S) are added to the 500.0 1111.. buffer (so dilution effects are negligible). What is the new pH? 9W7? MSW“ tic/W) Ma (refit WWW/«a; W...) Cwflwfi) M :2: , Zf/fi’me 12%;” (kc/(EM) file/OWEWJJ My (afiaffijii‘fif, 9F ya 0mg) Mcwecs Hay/(5;), 47» 5M 5 - "" m M M5“; __, I gHao/rgg,j«w mew] : fii W; mam L D -— ‘L a? W) USE Mm, W5” WW ; (W 7%”? firfi'fmwfflzfi] . 6 _. ML: 5/577 tfiwm 3 Name: V CHM 31 Second Hour Exam, Summer 2010 5. (28) Circle the letter that represents the best answer. i. What is the molarity of a sodium hydroxide solution if 25.0 mL of this solution reacts completely with 22.30 mL of 0.253 M sulfuric acid (H2804 (am) ? A. 0.113 M B. 0.226 M C. 0.284 M .451 M E. 0.567 M witL M V e .25, , ‘ mews 9: Wig-(4e .2. Wm M M ii. Given the following: M UL N20(g) + mm < == > mow) Kc m 1.3 x 10"13 For/l "~57 lief p0 N269 + 02%) <==> 2N0(g) Kc = X 10-31 W AIS, Find the value of the equilibrium constant for the follow/32g eqliilibrium Igection: W 9 a .. EH79?“ ' Nfig) + Vzoze) <:=> Noze) #90 “E37 Wk: 2’74”wa A. 7.0 x 10'44 B. 4.2 x 10“7 @4 x 10'E8 D. 1.6 x109 E. 2.6 X10"22 46’ .2 7" ,. [Q'._ “(7 a I w f1}; h I - LI w/ j - 50’ 5‘ :3 iii. Which of the following salts has the lowest solubility in water? "Y W I [V6 (K52 Values: Agzseo = 1-6 X 1049; Bi2S3(s) = 1-0 X 10’72; Hgsm 3 1.6 x 10'54; ._ Mg(OH)2{s) = 8.9 x1e"2;Mns(S)w 2.3 x1013) Hyman. ,y 7 efiflgfi 3 MW q A. Agzsw B. Bi283(s) @FLgS(3) D. Mg(0H)2(s) E. M11863 M495? .7: Lflga/MT-Z iv. List the following acids in order of increasing strength: H2$O4(aq), H28e04(aq), and HzTeO4(aq): M A. HZSeO4(aq) < Hg'fe04(aq) < H2804m) B. H28e04(aq) < HZSO4(aq) < HZTeO4(aq) C. HZSOqaq} < H2T604{aq) < H23304(aq) D. HZSOWQ) < HZSeO4(aq) < HgTeO4(aq) @HETeOtKaq) < HgSeO4(aq) < P12804810!) More: at W5 09er MW, .522 MW Met/’7" MW EcecWA/WW/Wf 5 > 5e > 72: 32 41cm gm)? ‘ {S M/ 54%;: Wm...“ firmq [3v SWfl/fiflr Name: CHNI 31 Second Hour Exam, Summer 2010 V. Which of the following is the correct Henderson—Hasselbach equation for an ammonia/ammonium chloride buffer, if K, for ammonia = 1.8 x 10'5? M6,, A. pH 2 4.74 + Loglo{ [N1313(aq)]/[Nfif(aq)]} ##3## “pm/{##1## % 7' a, MIC/Xi MV‘WCI B. pH »—~ 4.74 + L0g10{ [NH4+{aq)l /[NH3(aq)]} Mi? W) Mpg. WWW” @pH = 9.25 + Low [NH3(m)l/[N}14+(aq)l} Fit/‘6 “’4‘” $5 ’4‘" My? D. pH = 9.25 + Load [Natal/[man “#4 '3 “it” i 33. pH 2 14.00 - Logm{ 1.8x10'5} flea: "" “m (/54) 3' 7’35 may] at = 7“ ti WWW} Vi. The solubility of CaF2(,) is 0.00021 moles per liter. What is the solubility product (KS?) for CaF2(S)? 3-7 x 10"“ B. 9.3 x 10'” c. 2.3 x 10‘” I). 4.4);10'8 d 3 E. 1.2;;10‘“ ,7 a 2 Ca FaCS) c“ 0‘ ch) *’ ##1##) KjfbljaiiiifijlfiffiYZA/(E’Y) X 2% qémzljgn 3147?] 7" W Vii. Which of the following statements concerning aqueous solutions of salts is false? A. For any salt of a strong acid and a strong base, the pH will be approximately 7. 7760“? B. For any salt of a strong acid and a weak base, the pH wiil be < 7. 17600? -~ W416 WM/S C. For any salt of a weak acid and a strong base, the pH will be > 7. W9 “” 3 WW WW5 @For any salt of a weak acid and a weak base, the pH will be about 7. ““ /F W E. None of these is false. $0M I: SW5 56/17 [f 4 7 F {F were £4363 7.: g WW6 67??) > 7 ...
View Full Document

Page1 / 8

10_CHM_31_Summer_Exam_2_Answers - Name; K5 V CHM 31 Second...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online