Toupa Exam2 S05 key

Toupa Exam2 S05 key - {Arkwng Name Lab Sec TA Lab day/time...

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Unformatted text preview: {Arkwng Name Lab Sec. # ; TA: ; Lab day/time: Andreas Toupadakis, Ph.D. Spring 2005 CHEMISTRY 2B Section B MIDTERM 2 Multiple Choice (circle one) Instructions: CLOSED BOOK EXAM! No books, notes, or additional scrap paper are permitted. All information required is contained on the exam. Place all work in the space provided. If you require additional space, use the back of the exam. A scientific calculator may be used (if it is a programmable calculator, its memory must be cleared before the exam). (1) Read each question carefully. (2) For Parts I and 11, there is no partial credit given and only answers marked on this cover page will be graded. (3) The last page contains a periodic table and some useful information. You may remove it for easy access. (4) If you finish early, RECHECK YOUR ANSWERS! U.C. Davis is an Honor Institution # 1—10 (5 points each) Total Score (100) / 100 I 1—15 total points: Name (Page 2 of 9) MIDTERM 2 Part 1: Multiple Choice, Concepts (5 points each) Select the best answer and enter your choice on the cover sheet — No partial credit 1. Which is the strongest base that can exist in an aqueous solution? ©AT20055PR 2. Under ordinary conditions, a substance will sublime rather than melt if a. its critical point occurs at a temperature above room temperature b. its triple point occurs at a pressure below atmospheric pressure C) its triple point occurs at a pressure above atmospheric pressure d. its critical point occurs at a pressure above atmospheric pressure e. its critical point temperature is above its normal boiling point 3. Choose the Bronsted—Lowry acids and bases in the following equation: NH3 + CH3" 2 NH2’ + CH4 (:) acids NH3, CH4 bases CH3‘, NH2" b- acids CH3‘, NH2‘ bases NH3, CH4 C. acids NH3, CH3‘ bases CH4, NH2’ d_ acids CH3‘, CH4 bases NH3, NH2‘ e_ acids NH3, NHZ‘ bases CH3’, CH4 4. Predict whether an aqueous solution of NaF is acidic, basic or neutral and why. Na ‘2 (S) H10(€) Net-Z + F'( \ ——9 cm CW! . acidic because it is a strong acid basic because it is the salt of a weak base and a strong acid U' Q) . neutral because there is no hydrolysis O <:> basic because Na+ does not hydrolyze and F' is a base. e. acidic because it is the salt of a weak base NO+Cc1q\ ‘l' \-\3.0 ((3 a \no Yxm F'mcn + \410 (e) 22"— HP (mu + OH- Caql nge‘rc base 04 the weak 00263 Name ( Page 3 of 9) MIDTERM 2 _____—_.—____________________.______.—————————— 5. The equilibrium constant expression Kb for the following reaction: 6 C02(g) + 6 H20(1) 322:: C6H1206(S) + 6 02(9) is: [C6H12061 a KC = [H20]6[C02]6 [02] b KC = [CO2] [c0216 C KC : [C6H1206] [c0216[H2016 d KC : [02]6 \—\10 (€) [02]6 \no’v [email protected] (3 K3: Cgiime)6(§) [c0216 6. Consider the reaction: 2802(g) + 02(g) ;———> 2503(g) AH = —196.6 kJ The equilibrium is displaced to the left if: a. some sulfur trioxide is removed <::\\\"r <:> the temperature is raised Q§01C¢® {—Otcc“ :1§(Dg(b\+ . some sulfur dioxide is added (DQO . the pressure is raised ’Y . none of these answers \ add move Q, Name (Page 4 of 9) MIDTERM 2 7. If the reaction: H+(aq) + OH’(aq) —+ H20(l) is exothermic, and for pure water at 25°C is pH = 7, the pH of pure water at 50°C is: <::’ ©AT20058PR __________ a. pH = 0 ® pH < 7 H+com Jr OH'rucn : H106?) + Q c pH = 7 d. pH > 7 gh;"£‘\'§ {-0 {-he T e. pH = 14 3° '1‘ v“ i, add w0Y€ Q 8. C02 acts as an acid in the reaction CaO(s) + C02 32::! CaCO3(s) because it: . 1* 1- u a. turns blue litmus red u -- (a :0; .\. :O:C:OZ b. reacts with a metal c. is a proton donor K““””#———‘\“J¢ (:) is an electron—pair acceptor i t e.none of these 9. Human blood is: “ ". Cox OIC—O- a. neutral . C). k- b. very basic c. slightly acidic d. very acidic <:) slightly basic 10. The indicator HIn is red and its anion In' is green. The indicator changes color from pH = 6 to pH = 8. This indicator will be red in which of the following? -. PuYfililO “1 “_ Q ©AT2005$PR <\'\ f (D - a. pure water 6 @ 0.01 M HCl 1 1 8 9 l3 "i c. 0.10 M NaOH , i | —6 ; ' {4ievfi d. 5x10 M Ca(OH)2 Yea } I 0A e.none of these Mia?) Name ( Page 5 of 9) MIDTERM 2 Part 11: Multiple Choice, Short Calculations (8 points each) Select the best answer and enter your choice on the cover sheet — N0 partial credit 11. Given the following: N20<g) + 1/202(g) .:> 2No(g) KC = 1.7 x 10-13 N2(g) + 02(g> a 2NO(g) KC = 4.1 x 10-31 Find the value of the equilibrium constant for the following equilibrium reaction: N2(g) + 1/2 02(g) Z N20(g) KC = ? 5" 7'OXlO—44 N913) +01C3) <- QNGC‘M kcill.lxlo b. 4.2 x 1017 «“5x _ \ c 2.4x1018 1NO(8\ ‘LA N$O (<6\+'/ZOL(3\ kc:——— 43 d. 1.6 x 10-9 Hon e. 2.6 x 10-22 — -w , Nfi'al ’r IMOth ;—1 N10 (.33 12. 2.5 moles H20 and 100 g of C are placed in a 50~L container. At equilibrium for the reaction: C(s) + H20(g) 42> CO(g) + H;3(g), [H2] = 0.040 M. Which of the following is true at equilibrium? = _.. Qog { a. [CO] 0.020 M [Hicfli __ we :OogoN @ [H20] = 0.010 M 90 L c. no carbon is left \wo‘eC d. [H20] = 0.020 M (‘00 3C) 2 8.2 woé C l"). a C e. none of these Cm + \-\'LOCA3\ :fi Co cm + \~\1(«O\ ‘ wo€ wo'z (0-0§OM\ o M O M M + 0.0qu C ‘ ’1 0.0.6 “(9.0qu *0.0L\O M l M E 6.3 ewe ocqoM {D'OL‘O 0.0\OM '5\ H. :95th Name ( Page 6 of 9) MIDTERM 2 Ma km 13. What is the pH of a 0.253 M solution of ammonium chloride? Ka(NH;1 = 5.6 x 10-10 .\, NAM“, (men + H’LO 7;”); (OCH +NH’: (OCH [\A30+3 2 V Mo km '— \] 0.9.ng §.6xlo-'O S ’- .— (DQOCC‘DQJ LOLAJU'l-h-N KOCOU'IKOQ 2 '1 \.Q XIO‘" >' 1 -e ‘0 “9 (HMO O.L<. ~< PHZ—{oa (l-QXIO )3 : [+9 14. Twenty—five milliliters of 0.10 M HCl are titrated with 0.10 M NaOH. What is the pH before any NaOH is added? + _ a-040 H({ + H10 ——5 1*;0 + C1 b. 2.5 O M c. O 1 GAO M @ 1.0 . 25 + *‘ e p\_\:_,€03[fl303:-’€03\O 14.0 15. Determine the pH of a solution with initial concentrations: [HC2H302] = 0.100 M (Ké = 1.8 x 10-5), [HCN] = 0.100 M (K; = 4.9 x 10-10), and [HCl] = 0 100 M. a. 0.60 __;l . ‘ + b 1 00 H Cal-\301. (cq\ + “10(6) T— ClHEOtcucn + “KOCQm c 0.43 C350 M d. 4.74 (c1 \ + R10 Ce A — e 13.08 q ) : C N (oq\ {’ [420+C0‘H “.20 M Name (Page 7 of 9) MIDTERM 2 Part 111: Long Answer (10 points) Please show all work for calculations — Partial credit may be given 16. Calculate the pH of an aqueous solution of HCl l.OxlO‘8 M. For full credit make sure that you answer all 6 parts of the problem. ©15T2005$PR Solution \p-l: 1) Chemical equation for the complete ionization of HCl: (imam JV mom -—> (42,020“ + (e'ccm -9 IO M 29k 2) Equilibrium (ICE) table for H20 self ionization Chemical equation: 2H20(l) ‘—_—! H3O+(aq) + OH’(aq) Initial (M) no self—ionization of H20 ‘OX‘O’Q 0 complete ionization of HCl: I“ ‘ ‘ ‘ ’ ' ‘ _ ' — _ _ ' — '— Change (M) suppressed +7 +y self—ionization of H20: — — — — — — — — ~ — — — - — -— Equilibrium (M) concentrations: 2 Pk 3) If after the addition of HCl the equilibrium concentration of OH' ions is y (M), will it be or.y > 10'7? (Circle one) And, at equilibrium will it beor [H3O+] < 10'7? (circle one) \fi 4) Solve the quadratic equation for y: [momma : \o"“ (3H0'8H 1m” 31+ \0’8340'W :0 Com“ h=\o'6, 1'— 404M ~IO'Q + lo"5+L..|O-\q ytm .— 8 y== %.S XID’ Name ( Page 8 of 9) MIDTERI‘Q ‘p—E 5) Find pH: 3 : (BSXIO'S :COH'3 POH 1 ~€06CO¥V1 = '60?) (1),.g‘uo'e 321.01 (BUY: \L\-pOH : 60:8 pH : @> ’1 Pk 6) Which ionization, the HCl ionization or the self—ionization of water contributes more I-I+ ions to the solution and how many times more? More H+ ions: HCl or (circle one) (H+ from H2O) = Z times (H+ from HCl) FYow “9.0 951m, /V\ H20)" Name ( Page 9 of 9) MlDTERl‘42_ Periodic Table I H 1.00794 3 4 Li Be 6.94] 9.012“! 1 l 12 Na Mg 21W 213050 l9 2‘0 21 12v 13 1-1 25 26 27 k Ca Sc '11 V Cr “In Fe Co 39.11983 40.“?! 54.955910 47.98? 509415 I 54,9; l ‘ [$53-55 $331332“! 37 35 39 30 M 41 43 M 45 "i V . ’ ’ Rb Eur ‘r Zr Nb M0 c u Rh iii-3678 mm 85.90585 91.224 92.90635 9594 (9E) 101.07 10230550 1. 55 56 57 ’72 73 74 75 76 77 CS Ba La Hf Ta W Re ()5 1r DIEM” 31327 lllflJSS [71.49 1303179 183.83 131121)? 190.21 192217 87 “83 1’9 “14 105 I06 [107 if)! 109 l' r Ra Ac Rf Db 33% Bh Hs lv t (m) (226} (227; cm} ‘ : . - Some useful equations and data: PLEASE NOTE: Important values and equations required for calculations are given with the respective problem. The following may or may not be of any use. pH =—log[H30+] pOH = —log[0H‘] p — Kw =[H30+][0H_] szpKa + Kp : KC(RT)A" MM. (HCI) = 36.5 g/mole ...
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This test prep was uploaded on 04/05/2008 for the course CHE 002B taught by Professor Land during the Winter '08 term at UC Davis.

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Toupa Exam2 S05 key - {Arkwng Name Lab Sec TA Lab day/time...

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