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2008_05_30_14_56_57

2008_05_30_14_56_57 - Exam 2 2007 Give the best answer or...

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Unformatted text preview: Exam 2 2007 Give the best answer or closest numerical value. Kle/Vlfi L CLQW‘" g B FILL IN YOUR STUDENT ID NUMBER, NAME, AND TEST FORM=A You may not be seated next to a friend. You may not use a graphing calculator. One sheet of notes only. 1. When it snows, the pressure is usually less than 1.000 atm. at should be the melting point of ice under these conditions? (a) Exactly 0°C; (b) Slightly less than 0°C; lightly more than 0°C; (d) It depends on the amount ofsunlight; (e) It is only below 0°C at high altitude. I: t, '- l) 2. The phase diagram for Kr has a solid-liquid curve with a positive slope. Which ofthe following is true? (a) solid Kr has a lower density than gaseous Kr; (b) solid Kr has a lower densuy than liquid Kr; (c) solid Kr has the same density as liquid Kr; (d) Kr only sublimatcs above its triple point temperature; E— @ Kr only sublimates below its triple point temperature 3. Which liquid-liquid mixtures would you always expect to have a negative deviation fi‘om Raoult‘s law (i.e. lower than expected vapor pressure). (a) mixtures with endothermic heats of solution; mixtures with / exothermic heats of solutions; (c) mixtures of polar molecules; (d) mixtures of non—polar mo ecules ; (e) mixtures with very heavy molecules .4. In general, which substance would you expect to have the smallest AHvap and is highly soluble in H30? ' (a) Fe303; (b) sucrose (Clanou); (c) CH3OI-1; (d) benzene (0,116); @ CH3C00H ,. ‘ I 1. l ‘1 5. Arrange the following in order ofincreasin boiling point: NaF, MgClz, CH30H, CH3(CH2)3CH3? - @083011 < CH3(CH2)3CH3 < NaF < Mng; CH3(CH;)3CH3°< CH30H < NaF < MgClz; ' CH3OI-l < CH3(CH;)3CH3 < MgCl; < NaF ; (d) CH3(CH1)3CH3 < CH30H < MgClz < NaF (:1) some other order 6. A nonelectrolyte compound has the empirical formula le-igFe. A solution of 0.255 g ofthe compound in 11.12 g ofbenzenc(C51-15) boils at 80.26°C. The boiling point ofpure benzene is 80.10; the Kb is 2.53 ”Cl'molal. What is the molecular formula ofthe compound? (a) C5H4Fe; (o) CmHgFe; (c) ClsngFe; .cmnmroz; (e) CaqulFes . F93"? a} 7 What mass ofethanol, C3H501-l, a nonclectrolyte, must be added to 101. ofwatcr to give a solution that freezes at -10 "1? Assume the density ofwater is lg/mL and Kr= 1.86 “Ct’m (a) 85.6 kg; (b) 24.8 kg; (c) 5.38 kg; 63 2.48 kg; (e) 1.17r kg m A 0.0100 g sample of Cr(NH3).t(804)Cl (Mole Wt = 251 ) is dissolved in 25.0 ml of water and the osmotic ‘pressure ofthc solution is 59.1 mm Hg at 25“C. How many moles ofions are produced per mole ofcompound? (1'60 tort = latm, R = 0.082 L-atnu‘mol-k) (a) 1; 2; (c) 3; (d) 4; (e) 5 ‘- '2'? (In: {hi—TN] :0“! ,u' - ” “Liv i. '-‘ -lt) 951.1 22!. 382.10%!“ . a l.) (lilo __.. 9. For which ofthe following could you expect both the solubility in HEOJIo decrease with increasing __ 1-- _/-_ . temperature and should have a negative entropy of solution (A5”. < 0): K1504, NaCl, CH3CHgOl-l, 03 @only K2804; (b) only NaCl; (c) only CH3CH20H; ‘@ only 02; (e) 2 or more Which of the following woul you expect to be insoluble in both water and benzene (CGHS)? gCl (#5 inset; (c) can; ( Cl-13COOH; (e) none 11. For the following reaction: O;(g) + 2N0(g)<-—> 2N0;(g) Starting with only Pi‘l‘ (N02) = 0.500, at equilibrium the / total pres re was 0.674 atm. Calculate the eguilibrium partial pressure of N0;(g) in atm. @0174; (b) 0.163; (90.150; ( )0.087; (e) the reaction cannot go backwards {. l2. Which of the following is [email protected] shift reaction equilibria toward the side of the products; (1:) catalysts speed up reactions; (e) reaction rates depend on temperature, reactant structure, concentration of reactants and the presence of catalysts; (d) exothermic reactions can have activation energies; (e) highly exothermic reactions usually have a large equilibrium constant 13. Ba3(AsO4)2(s) 6> 3Ba‘3(aq) + 2AsO4‘3(aq). If a large amount of the solid is place in H20, the equilibrium concentration ofthe Ba‘2(aq) will be 3 x 10'3 M. Calculate the equilibrium constant in M5. - 45, 43, .-' «l3, 4:, .11 {9 1.0:: to , (b)6.0x 10 , @143: 10 , (d)3.l x 10 , (e) 1.1 x 10 14. K = 2.5 x 10'” CaC03(s) e> Ca‘?(aq) + co3"(aq). It‘initial we have 66.6 g ofCaC03(s) in a IL solution oncofi] = 0.3 and [Cafl] = O, calculate the equilibrium concentration of [Ca’d]? .43) 8.3x 109; (b) 4.1 x to"; (c) 9.3 x 10'“; (d)8.3x10"°; (e) 4.1 x 10'? present at equilibrium? _ .- aising the temperature or decreasing the volume (b) raising temperature or increasing the volume; (c) lowering the. emperature or Increasing the volume ; (d) lowering the temperature or adding 502; (e) raising the temperature or adding 8020b 15- 502%) + 02(3) =>‘Cl;(g) AH,=10KJ Which of the following actionsvwill both decrease the concentration of CI: gas 16. For which of the following reactions is product form lion favored by low pressure and high temperature. (a) N2{g) + 3 H2(g) <=> 2 NH3(g) AH” = -91.8 kJ; 002(9) <=> 2 00(9) + 02(9) AH“ = 566 kJ (c) Haigi + i2(g) <=:~ 2 Hl{g) AH“ = .9.4 kJ: (d) 3 02(9) <=> 2 Oafg) AH” = 235 N (e) Nztg) + 2 02(9) <=> 2 NO;(g) AH“ = 86.4 N ti". Use the set of reactions and equilibrium constants provided to determine the value of K for the reaction: 2NH3(§)<=>N2(3) + 3Hz(g) .. . _ _ E15 less than 0.01; (b) 0.01 to 0.1; 2NH3(g) + 4i‘I-10tl)<—>2N02(g) + 7142(3) K_ 4'35 (c) 0.01 to l; (d) l to 10; ’ [:30 L.— N2(g) + 20;(g)<=>2N0:(g) K= 0.143 (e) more than it) H10(l)<=>l-l2(g) + 1 902(3) K: 3.44 i l - isn‘t r 7f- _ ‘it i 'l ' H?) 18. Kc = 0.353 at a given temperature for NO(g) + 1IZCI2(9) ¢->NOCL What concentration of N00] must be put in a 6.66L vessel in order that the equilibrium concentration of OCI equal 1.00M. All other initial concentrations are zero. (Hint. let the initial NOCI cone be "C" an unknown) a) .5M: (b) 11M; ©2.5M; (d) 1.3 M: (e) 2.3M; 19. Which of the following is a true statement about the following reaction: ZBrtg) <-> Brfitffifilhe equilibrium constant is “greater at low temperature: (bf the equilibrium constant decreases as the volume of the' reactor is decreased;__ ( AS” > 0 ; @the equilibrium constant is greater as the volume of the container is increase; ,(e) AG“ (1 atm, 298K) > 0 V’ 20. A catalyst can be described as a substance thatK-(B provides a path of lower activation energy for the reaction; (hf lowers the potential energy of the products with respect to the energy of the reactants; (c) increases the number of collisions of reactant molecules; (Id) increases the kinetic energy of the reactants; /(ea undergoes change to accelerate the rate of the reaction 21 {2-5 pts) When does Q=K? a) When AG” = 0; (b) When AH“ = TAS"; (c) When :30” = AG; (d) When AS°= 0; (e) none of these. FILL IN YOUR STUDENT [D NU BER. NAME, AND TEST FORM=A \(t/(Mmg L Lixéwx g B Tests 2007———-Give the best answer or closest numerical value. FILL IN YOUR STUDENT ID NUMBER, NAME, AND TEST FORM=A; You may not be seated next to a friend. You may not use a graphing calculator. One sheet of notes only. You may not possess or touch a cell phone' In your possession during the test. 1. Which of the following statements is false: (a) The hydronium ion is the strongest acid species that can exist in aqueous solution.; One cannot distinguish the relative acid strength of HCI, HBr, and H1 in water; (if; The conjugate of a strong base is a neutral cation; (d) at pH = 7. H;O autoionizes 100% to form H30‘ and OH' species; (e)’all strong acids are Bronsted-Lowry acids 2. The pK. values for HCNO and HNO; are 3.66 and 3.35 respectively. Therefore it follows the HCNO is a \ f 5! acid than HNO; and CNO' is a 5 base than NOZ'. @veaker, stronger; (b) weaker, weaker; (c) stronger, stronger; (d) stronger, weaker; (e) not enough information is provided to answer this question ‘ ‘ (LL 1T p . h u .1 3. Which of the following has the strongest conjugate base? (a)I-lC10; (beBr; @HBrO; (d) HCl; (6 HI (hint there is no H—Cl bond in HCIO) ii. p. tl \lr 47¢ What change will be observed in a DJ M HOBr solution if a small amou ofNaOBr is added? HOBr + H10 '—) OBr‘ + HJO‘ the percent i nization of the acid will decrease and the pH will decrease; ( the percent ionization of the acid will increase and the pH will decrease; he percent ionization of the acid will decrease and the pH will increase ; (d) the percent ionization ofthc acid will increase and the pH will increase; (e) the pH will increase and [HJO‘] will increase; 7 f, {4 DE, A [\‘(0 ()1 I 0' 5. What Is the hydroxide Ion concentration of 0880 M CN'? The K of HCN iS 4 4 x 10 '° (a) 5.2xio’- (b)4.5x10“' (c)s.;2xI0“ (d)4."5xio;(c)4.4xio‘° kg: LLLMD'” HCN —l OH ~7 CN ill/O (He‘ggrvl .J - ‘0 ya: q('v{tle :____.’- C 6/ Which of the following pairs cannot exist in +large concentrations simultaneously In aqueous solution? “ow NH4+ and Br'- @/ 30+ and OH' , (ej’NHf’ and NH); Joli/NHf' and HP; ([6 HF and HCI; c/jw' mi: or. if» 7. Consider the following salts. Which one(s) when dissolved in water will produce a brute solution? I) 0.666 M R‘bClOi; 2) 0.0666(M NaNOz; $0.00666M NH4CI (a) only 1;.nly 2; (c) only 3; (d) l and 2; (e) l and 3 8. Which is the weakest acid? (hint, they are all oxyacids)®\1aHSeO4; (of H2804; (6 KHSO4; (d) 1123604; (ty’HCIo. (Q A o.Io M solution ofacid HA is 62% ionized. What is the Kb? (:1) H x 10'”; (b) 1.0 x IO‘”; (c) 1.9 x 10‘”; @ 2.I x 10'"; (e) 1.3 x 10'” m - Z (9_:\J:EJ iOO 1/— 2.?‘l'l0 .l "4 ‘ ~lll \\ 1‘1 5: (1, 60. Ascorbic acid, H2C6H602, IS a diprotic acid. The K and K; values are 7 9 x l0'5 and 1.6 x I0 '2 respectively. What Is the HC6H602 ion concentration in a 0.10 M solution of ascorbic acid? (a) 7.9 x 10"- , (b) 5.6 x 10 2; (c) 2.8 x 102; .3 -3 \ (d)2.8x10 (e) 5.6x lO [Hcki’iuoz ’3:’l ii v t a. 0 .l i I ‘6 - ’ (r u ‘- 6‘" ’ i) 1 RV) . i hr 1 I. In which of the following solut' II will HI have the greatest percent ionization? (this question is very French!!) (a) 0.1M HI dissolved in DJ M HCl; 3“) 0.1M HI dissolved in 0.2 M HCI; (97 0.1M Hi dissolved in 0.1M Nal; (d) 0.1M Hl dissolved in 0.2 M Nal; c all would have the about same (+l-l%) percent ionization iii -an ML 12 What is the pH when 25.00 mL of 0.10 CH3C02H is mixed with 24.0M of 0.100 M NaOH. (K. = 1.8 x 10") (a) less than 5.00; (1)) between 5.00 and 6.00; etween 6.00 and 7.00; (d) between 7.00 and 8.00; (e) above 8.00 i)“ I i ngi .i (”3(1) H ~< C ”((01)“ 1 0‘4 _9 u (00 L”! D 226.1 .1 About M = '.8-'0 5..» 2H C E) 36 .I O 2.“! : 1.. 7 s ki RH ‘15!“ l°3217 : p.127 13. What is the [email protected] (not pH) of a solution of 0.81 M acid and 0.35 M of its conjugate base if the K, is 5.45 x 10.3? (a) 6.67; (b) 7.30; 7.10; (d) 6.37; (e) 7.58 5 €i‘\:<it2()k ioflt’a‘l 7' L'q f- 14, 7 Which of the following pairs of}? exist in large concentrations simultaneouslg‘in aqueous solution? (a) NHJ and HF; (tn/NH, and HCI (c arise. and NaOH yi) HC1 and NaOH; @fiNazHSQ and HCIO. V‘lb \’i A 1))! b) S“ I 1 (JV: ‘UM S b 1 I?) .2 1 tr:l i K, Ii ( iii (15‘. A 2.00 g sample of acetylsalicylic acid is dissolved in 100.0 m1. of water and titrated with 0.200 M NaOH to the thymol blue Viequivaience point. The volume of the base used is 55.5 mL. What is the molecular weight in grams/moi of aeetylsalicylic acid assuming one dissociabie proton per molecule? (hint first calculate the emacid, then use the initial volume to calculate the original moles of acid, the use the mass to calc the molecular weight). (a) 168; (b) 188; (c) 194; ® 180; (e) 172 31/1 1 H10 ~—7 0,11 ~41 c - 190 «a \| D . _ tit 16 1f 66.6 mL of 0.0666 M acid solution were titrated 0. 66.6 ml. of 0.666 M KOH, ‘which will have the highest pH at the equivalence point. (a) HCloz; (b) HOCI; @Ni‘h; (d) HBr; (c) all but one would have the same pH W For 11:80, at 25°C, K“ = 1.3 x 10'2 and 1t.2 = 5.6 x to". If 50 ml or 0.1 M H250J is titrated by 60 mL ‘ of 0.2 M NaOi-i. what is the pH . (a) 6.3 or less; (b) 6.6; (c) 7.3; (d) 7.9; (e) 8.3 or more. 1220+ +2“ 9 2266+ 226+ 60 -+ :60 + :6; 9‘6 2 7.2 r g.....[ Vim-l O CO 3 oo 6 Q 2 o ‘i Sr 00 3’ 2 “$0.. . 011'" (2 1 '1' () fii " i176) * iCr/J ' ’ ‘4 ' in 18. How many grams of NaOH (MW = 40ymol) is required to make a pH = 3.00 buffer from 0.666 L of 0.666 M HF (7.2 x 10") @1045; (b)!5.l-20; (c)20.1-25; (d)25.1-30; (e)1essthan100rmorethan30 1A 1‘16 6 01.1., 6 211,0 , C in .‘M Q “5 ($5 3: 3i” * i170";-1 ‘ C ’ ( ‘ L A .‘121: 5 r44 «77 f, ‘4’}1 4,11 '5.” 19. Which one ofthe follow is a buffer with pH < 7? K,(HCN) = 6.2 x 10'” and Ka (HF) = 7.2 x 10‘4 (6)10 mL or0.| M HF+ 10 mL 010.1 M NaOH; (b) 10 m1. or0.1 HF +10 mL of0.l M 1-1CN; (c) 10 mL of0.1 M HCN + 6.66 mL 010.1 M 1-1Cl; (a) 10 mL of 0.1 M HCN + 6.66 mL 010.1 M NaOH; @none “‘2‘“ 0‘. r 20 if a large amount of strong acid is added to abuffer, the buffer will fail and pH will greatly decrease. What is the reason: Wigh high concentration of hydronium shifls the K, of the weak base; CK) all of the weak acid is convert to weak base; (c) all of the / Weak base is convert to weak acid; (0) the moles of weak acid is insufficient to match the moles of strong acid being added; (e) the K, of the weak base is too small. \ t L a pin L FILL IN YOUR STUDENT ID NUMBER, NAME, AND TEST FORM=A; ‘ ...
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