exam3-answers - Problems 1-6 are 3 points each. Circle the...

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Unformatted text preview: Problems 1-6 are 3 points each. Circle the BEST answer. Problems 7-16 are 8 points each. To get credit, you must show enough work to demonstrate that you know how to solve the problem. 2 pts for seat number! 1. What is the order of with respect to 03 and the overall reaction order for the reaction with the rate law: Rate = k[03][02] ? 2] 3and3 3] 2and3 4] land3 5] 0and2 2. The reaction A + 2B —-> Products was studied and found to be first order in A. Further study showed that when the concentration of B was quadrupled, while A was held constant, the reaction rate increased by a factor of sixteen. What is the rate law? 1. Rate = k[A][B]2 2. Rate = k[A] [314 3. Rate = kIA] [B]16 4. Rate = I‘c[B]2 5. impossible to tell 3. The energy from the radioactive decay of tritium is used to illuminate exit signs that are posted in many buildings. The manufacturer adds 8 times as much tritium to the signs as is required to meet the brightness that fire codes require. If tritium decay is first order and the half-life of tritium is 12.5 years, how long will the signs meet the fire code? (SHOW WORK) 1] 25 yrs 2] 12.5 yrs 4] 50.0 yrs 5. none of these 4. A positive value of AG" for a reaction indicates that: 1. the reaction favors formation of products. 2. thgflflMss ontaneous. , vf- . . the reac ion is nonspontaneous. 4. the reaction is at equ ibnum. 5. the reaction cannot reach equilibrium. 5-. Which thermodynamic statement listed below would confirm that a chemical reaction is spontaneous as written? 2. AG>O 3. AS <0 4. AH>0 5. AH>OandAS <0 6. Graphical analysis can be used to determine the rate law for a general reaction of reactant "A" going to products "B" and "C". Which of the following Time-Concentration plots showu below would be expected if a particular reaction follows a second order rate law? Ln[A] [A] \ Time Time 1. 3. Ln[A]\ 1/[A] Time Time 4. 5. 7 . In a powerful laser beam water decomposes into its elements, producing hydrogen at the rate of 0.12 mol/L-s. What are the rates of appearance of oxygen and the rate of disappearance of water, and what is the rate of the reaction? ’lH'LO 3? 7— HL +‘ 0:. raia='-L AiHLOZI = L ASE-11:1 = Afpfl 2- _______._ 4+, _ L. a HM] L bk 8. c ' deHhe-react-ion-of—carbonmonozgide and chlorine gas to form phosgene as shown below? CO (g) + C12(g) —> C12CO (g) Given that AS°m1 = 47.0 Jmol'lK'1 and til-1°,“ = -220. kJ/mol for this reaction, what is the standard Gibbs Free Energy, AG‘LX11 for this reaction at 500 K? Ag”: _LH.O T =' W o moll< AH = “7.10 in; :. 110000.13; Mot MOI man": AB” - TAS’ : 17,0000 gt .. ('50 9E(" of] if}; ,— .—. 9. What is the equilibrium constant, Ki,cl for the following reaction at 25 °C, given that AG° = -16.8 kJ/mol? H2 (g) + 12 (g) <=> 2111(8) A66”: ~P~T \nkup — Mag 2 —- (fi-Blax153fl)<fl$p) \“ Vets ham moHL $O\U€ gar \RM% 2 7:14 \Lepgze 10. Consider the reaction in aqueous solution: 31 ' + $203} —> 13' + 28042-. Under a given set of conditions, the concentration of 13' changes from 0 to 7.6 x 10'4 M in 10 seconds. Calculate the rate of disappearance of I' for this time interval. At 3 At billy] 1.6thq~0 _ 7.63065 *9 l - = —— ' 1.2mm ='“A———E;3 A 1: L0 _ L( 3 At a - Dfismo 2 Am 11. The rate constants, k for the following reaction were measured at two different temperatures as listed in theat table below. CH3COOC2H5 (aq) + OH' (aq) —> CHgCOO' (aq) + CszoH (aq) 25 1355 L What is the energy of activation, Ea for this reaction? 12. Use the following data for NO + C12 —> NOC12 to answer the question: Initial concentrations, (M) Initial Rate M [£21 mollL-s 1 0:9}0 0.05 0.05 e949 0.102 2‘ 0.20;? Ll mitt 1 Jr’— CN OquL] 0.020 0715‘ 0.90 ‘ 0.0303“r5 chi-5‘ 1.351) " 5 (a) Write the rate law in terms of k, [NO], and [C12]. (b) Calculate the value of k. K it \lOQJJJL/J {L Qak 000M ‘LQDMLQEA 13. The decomposition of hydrogen peroxide to water and oxygen is a first order reaction with a rate constant of 0.0410 min'l. If we start with 0.500 M H202, what will be its concentration after 20.0 minutes? 114101 ‘3- 0). +1HLO \n [a] = \n [A], — Kl; ‘_ \nU‘a = in (05) e (D -0‘110X10; 4.61) \nflflzrla Dc]: QC @2 0.110155 14. A biochemist studying the breakdown in soil of the insecticide DDT finds that it decays by a first order reaction with a half-life of 12.0 years. What is the rate constant, k for this first order process? t‘ _ in (l K = ‘2 h. ’ 1K ‘13! :1 1?- I) L: O i 057 is How long does it take DDT to decay from 295 ppbm to 50.0 ppbm? [do not make this hard, ppbm is a concentration] lob]: \nEPCla '- LT \nteo] = In [29:53 »— o O‘S'l‘z‘sT score 9C? 15. Using the entropy values in the table below, what is the change in Standard entropy, AS° for the following reaction? 2 CHgOH (g) + 3 02 (g) —-> 2 C02 (g) + 4 H20 (g) A80: — —: was; 3/{4 16. The following reduction of F6203 to Fe occurs in blast furnaces during the steel making process: 3C0(g) + Fe203(s) —> 2Fe(s) + 3C02(g). Calculate AS0 per mole of Fe203 reacted, if the values of 8° for C0(g), Fe203(s), Fe(s), and C02(g) are rxn 198, 87, 27, and 214 J/rnol-K, respectively (answer in units of JK). Ago: ZWCQMLQF " 2M 5{L5 'S/K EXTRA CREDIT: A. 2pts The reaction A + B —> Q was thought to occur according to the two step mechanism: A+Bi>c C+C—kz——> Q If the rate law is determined to be: Rate: k[A] [B] then, 1] step two is not needed for the reaction to occur 2] step two is much faster than step one 3] step one is much faster than step two 4] step one is not needed for the reaction to occur 5] none of these B. 5pts A chemist carried out the reaction A —> B + C. As the reaction proceeded, the data below were collected. By graphing in the stepwise manner discussed in this class, determine the general rate law for the reaction (Rate = k[A] x) and state the order with respect to A. Show your graph(s) below, being sure to label your y-axes and state the reason for the rate law you write. Please circle your two answers. time seconds LA] 10 0.245 20 0.0899 CA3 30 0.0326 +m~_ 40 0.0120 \thfl \ “hm C. 5pts Suppose you have an exothermic reaction with AH: -15kJ and a AS = +150JIK. Calculate AG and Keq at 100K Mr: 45ch 21500014 : [Soo— AS TE ASL—w Aaan—Taa *PSV. ) AG]: “30000 T ef- 9‘1— ...
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exam3-answers - Problems 1-6 are 3 points each. Circle the...

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