14F_C104_Exam2a_key.pdf

14F_C104_Exam2a_key.pdf - NAME CI-u104 Fall 2014 Exa...

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Unformatted text preview: NAME CI-.-u104 Fall 2014 Exa @ October 23,2014 Lulu C C k0 f I LAB SECTION I. (20 pts) Write the correct answer in the space at the left. flfigmechfifo 1, lmoQa Eli? 2. . . , 3. ‘f'qttZlmé Pomi' JEPICSSWM Z22 TE“ l0,¢i§d~% Second mole: 5. _M_ 6. Concen‘iMCLhow/x 7. 8. ITOMEQJ (1i use, dq ham'iC 9- teaciten Quoi‘tea‘l” ((1310. mankind‘s) 1 1. mien dimer” 12' Le x 10"” 13. (gag‘uga‘ie base. 14, Parq‘fl'alitt (r-momflelcig ) 15' LX156. Shift-23m 16. ibm Qflaiwc, 17_ in! dNol 51's 18. M 19. (lid-0W“ EQL“ donor“ 20' According to the 2'1d Law of Thermodynamics “the entropy ofa closed system never ” A measure of solution concentration defined as nsnhne/lllsmvem is called the A colligative property effecting the solid/liquid phase transition of solutions is called The vapor pressure of an aqueous sucrose solution with xsucmse = 0.05 at 100°C is The rate law -d[A]/dt = k[A][B]2 belongs to a reaction that is in [B]. The units of the rate of a chemical reaction are The halflife of a first order reaction is unique in being independent of The Arrhenius equation specifies the dependence of the rate constant. The notion that at equilibrium the rate of the forward reaction equals that of the reverse reaction is called equilibrium. When not at equilibrium, the ‘law of mass action’ expression gives values called the ’. Le Chatelier’s principle states that a chemical sytem at equilibrium an imposed change. In the context of the Brensted—Low1y definition, an acid is a At 25°C, the ion product of water (Kw) has the value Hydroxide ion is the of water. The criterion of a ‘weak acid’ is that it is dissociated in water. The base isonization constant Kb is a measure of Equilibrium constants change with Due to a solution of NaF is mildly basic. In pure water at 25°C the value of —log[H30+(aq)] is A Lewis base is defined as a(n) CI-IEM104 Fa112014 Exam 2A October 23, 2014 NAME LAB SECTION II. (15 points) Put the letter of the correct answer in the space at the left 1. As T increases, the solubility of salts in water generally? J— A. increases D. goes through a maximum at Tcril B. stays constant B. goes through a minimum at Teri: C. decreases B 2. Molarity is a measure of concentration (of x) defined as? A- nit/Insolvent 13- nx/Vsolulion C- nx/rnsolulion 13- Inx/Vsotution E. nx/nsolvent 3. The vapor pressure of a solution of a nonvolatile solute is given by B A- H : 1111K], 13- Psoln = Xsolvcnt 'Posolvent C. Pvap = '10g(P0) D. H = MRT E. PV = HRT 4. Which of the following is an example of an ‘integrated rate law’ D A. ud[A]/dt = k[A]2 __ B. rate = flAjHVBJdt C. 1n k = {Ea/R) + lnA D. ln[A]‘ : —kt + ln[A]0 E. pk = wlog(rate) E) 5. Which of the following rate laws is overall second order? A. rate = k[A] B. rate : k[A] [B] C. rate I [A]2[B][C] D. rate = [A] [B]2 E. rate = [A]/[B] 6. For a first order reaction (A —> B) with i< 2 3.7 s], what is the half life At A. 0.193 B. 1.853 C. 1.31 s D. 0.693s E. 0.53 7. For a first order reaction (A —> B), A = 3.0 x 10” s'] and Ba = 22.7 kJ/mol, what is the rate constant at 25°C? C A. 8.2::(10'63'1 B. 5.3)(103M'IS'1 C. 3.2)(1078'1 D. 2.7x 10'“ E. 6.0x 1023 5-1 8. According to a rule of thumb, close to room temperature an increase in T by 30°C: D A. decreases rate by a factor of 10 B. increases rate by a factor of 2-3 C. decreases rate by a factor of 2—3 D. increases rate by a factor of 8-27 D. increases rate by a factor of 303.15 CHER/1104 Fall 2014 Exam 2A October 23,2014 NAME LAB SECTION 9. Upon diluting the solution of a weak acid by a factor of 10 its ‘percent dissociation’ B A. decreases B. increases C. stays constant D. is 100 % E. is too small to be determined 10. The equilibrium constant for the hydrolysis of bicarbonate (I-IC03'(aq)) is: A. K = [OI-1’] [H2C03]/[HC03‘] B. K m [HCOg']/[HgO"‘][C032'] C. K= [HCO3'][OH']/[I-12C03] D. K : [H20}[HC03']/[CO32'] 13. K. = [Hzcog][0032‘1/[Hcog']2 11. Which is true of the equilibrium constant for any reaction Q :4 A. It does not depend on the temperature. B. It does not exceed values of 6.022 X 1023 C. I does not depend on initial reactant concentrations D. It was invented by M. Le Chatelier E. It is always larger than the reaction quotient Q 12. The relationship between KC and K], is ——[—\--~—-— A. K], = KC(RT)“" B. K], = KC(RP)" C. ch = -pr D. K], = KC E. KP = KC'P" 13. H2804 is E A. bright yellow B. a weak acid C. a strong base D. the conjugate acid of 803 E. a diprotic acid 14. Which is true for conjugate acid/base pairs B A. Ka/Kb : 14 B. Ka'Kb = 10““ C. pk.a /pK;, : 14 D. Ka+Kb=Kw2 E. Ka:t<b= 1.0x 10'7 15. Which of the following molecules is net a weak acid I-IF HI HOAc HCN NH4+ muowa CHER/1104 Fall 2014 Exam 2A October 23, 2014 NAME LAB SECTION SHOW WORK FOR FULL CREDIT ON PROBLEMS III. (25 pts) Kinetics. The data below were collected for the reaction: 2N02(g) + F2 (g) ’9' 2N02F (g) a. (15 pts) Give the rate law for the reaction. What is the overall order of the reaction? ”A '- Lfilcbwlwl I [N031 “inhibit“: t: nit, (leaflet: an“? \aiwlw'm [114021 225$ '. D4011 (ambled [LE3 claw-rel -. r'ml‘f, CJDllelflfi.) may (Mm (m YE\ ovate.“ Zwl (31%“ Yale p< l: NOJEW] ’ Anglia»: Wflflttfl 2““ 640%,!“ b) (10 pts) Give the value of the rate constant (units!) . u t in. rate, a 0:2 [WALES Q”; A @316ch L 3- . M {DH/k Ll : 6-H“ ”:33“ " g m “wwmmwwmflww “rm: 2.?!2 M ‘5'” 0mm . 19.me Ans. 2.5?“ Mil-”.5”: CHEM104 Fa112014 Exam 2A October 23, 2014 NAME LAB SECTION IV. Equilibrium (30 pts). At 2000°C, N2 and Oz react to produce NO. a. (8 pts) Write the balanced reaction equation and the equilibrium expression (in terms of pressures). Marcy + 0533 we 1W3) EL pile b. (7 pts) An 1.00 L equilibrium mixture of the three gases contains 0.500 atm of N2, 0.500 atm of 02, and 0.156 aim of NO. Calculate K1,. Ans. kt} ‘x‘ O'0(§¥“ c. (15 pts) Maintaining the same temperature, the volume of the same gas mixture is expanded to twice it original value, i.e. 2.00 L. What are the new equilibrium pressures of all three gases? PM) “:2. 94:36.”. as 0%?g aim 5—,“ ® are m Qfigfl‘ are 2530 Chiba m- ( . w loeyfl ‘ E3». 3M Q 0" 051500.530 O 71 PM... MM MM m 0.3.650 aim \ __ . ‘1 Hal \ 3% Q}? l4? , ll/rafxv‘mcxecilmrtlwws Remixes 0? 8m OUL boil/x $\0‘€&) Chafing-“HQ. W$$mnfiw (ith ho‘r PM) a: 0.0;3‘8 aLJUM Pg“ 2 0.2500-M Chm/139,.J‘LL lmglhw are Q'Clw‘h “mm‘ Anew CHEM104 Fa112014 Exam 2A October 23, 2014 NAME ' LAB SECTION V. Acids and Bases (30 pts). a. (5 pts) What is the pH of a 0.065 M solution of NaOi—I? "ill {om w. 0.0196511 ._~, gangs 332*? : Lsa— x 10""‘3 pH: 12.8\ 0,05 Ans. Ell“ 1Q,8l b. (10 pts) What is the pH of a 0.12 M aqueous solution on HClO (Ka = 2.9 x 10‘8) HERD 4» “LCD "ta-ti CLO-Imp ~t~ 1430*co%\ lg : [lifflgg‘flm time our M304. LHcmj " 1 on; 0 o C. tux «+3 +x 2‘ n. in “a is =» Jim-W r. 2mm 3 ‘1’ W X X x ( 0.12% K2“ m Zfibx “34.0 12,: BHEXHYBS X” Bfimufsfifw ‘1‘):118 H: [+213 C «wrowwa‘l‘tun U586“ - ' c. (15 pts) A solution is prepared by adding 50 mL of a 0.100 M NaOH solution to 100 mL of a 0.050 M HF solution (KAHF) = 3.5 x 10“). What is the pH of the mixture? NQOH(GC%\ "1““ HFffiS‘.‘ “$3 NQ+(G.%\ '1“ Flag?» + H29 5’0va 0.100»! wwbofia [Fl a 3.995- .311”: 0.933 M :3 0.00%: mois- u camogmiq, Q, 1501. m> Q“ Hi: \flan imam haiilcqnflz'ml was Kwuimina Somalia I»... 0.0953!“ M F" 0%me: " w «W3 \A (in sis F + 1-130 tfi‘ W + film '1 W k ”N 1.0xio" W Vb” EEEEL m "MM“ 1, m mar“ 1w =3» "saw L1: 3 mom mg ”" in: on“ 2 1.01 x \o .1, 09.0% c) .3; C -=->< +x +x ‘ E3; now-ax x >< Ans. its: 32.98% 1. N ”n lg is.» W...” a 25x10 6 b 0.033 - l f? B -l X1 we 2.%xio“‘"- 0.053 2 93* x 10 K W»- 8‘8 K \O—% :2? [OH-”1 Lawtox\‘m&'l‘uiu “$534) NAME POINTS: H: 111: IV: Total: CHEM104 1321112014 Exam 2A October 23, 2014 LAB SECTION SCORE 120 ...
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