7#d0d000000)0)0)0)0) 03 0=0=0=0=0= 0w0]0]0]00w000]000000 Great Expectations Sheet II CH142, 1996 1. Given the initial rate data for the reaction A + BC, determine the rate expression for the reaction. [A],M [B],M D[C]/ Dt (initial) M/s 0.10 0.20 40. 0.20 0.20 80. 0.10 0.10 40. 2. We are studying the reaction, 2 AB, and find that the rate expression for the reaction takes the form D[A]/Dt = -k[A]2 . If we begin with [A] = 0.100 M and find that after 368 sec, [B] = 0.0400 M, what is the value of the rate constant, k? 3. Calculate the activation energy, E*, for, 2AB, given k (at 300 K) = 1.64 x 10-3 and k (at 500 K) = 3.86 x 10-1. 4. The substitution of an I- by a Cl- on H3CI can occur by two possible mechanisms: Mechanism 1: step 1. H3CI H3C+ + I- ; slow step step 2. H3C+ + Cl- H3CCl; fast step Mechanism 2: step 1. H3CI + Cl- H3CClI; slow step step 2. H3CClI H3CCl + I- ; fast step A) What is the rate expression expected for mechanism 1? B) What is the rate expression expected for mechanism 2? 6. We examine the reaction of AB, which displays first-order kinetics. We know that k = 0.30/min. If we begin with [A] = 0.54 M, what will [B] be after exactly 7.00 min? 7. We are studying the reaction of 2A 3B. We make a plot of ln[A] vs. time as the reaction proceeds. This plot turns out to be linear with a slope of -0.25/s. What is the rate expression for the reaction? 8. Radioactive material decays by a first order process. That is, the rate of decay is proportional to the number of radioactive particles present. The quantity of a radioactive material present is directly proportional to the number of disintegrations observed (per minute or per hour, etc.). Let us say a sample of radon gas emits 7.0 x 104 alpha particles per second the first time you make a measurement. After 6.6 days, you find only 2.1 x 104 alpha particles per second. A) What is the half life of radon (time required for half the radon to decay)? B) If you examine the radon sample after a month (30 days), approximately how many alpha particles per second would you find? 9. What is the rate expression for the reaction, 2A + 3B 2E, given the mechanism below: step 1. A + B C; slow step step 2. 2 C D; fast step step 3. D + B E; fast step 10. Calculate the activation energy, E*, for, 2 HI(g) H2 (g) + I2 (g) given k (at 600 K) = 9.84 x 10-9 (M-1s-1) and k (at 800 K) = 5.56 x 10-6 (M-1s-1) 12. We have the following equilibrium: 2 SO3 (g) 2 SO2 (g) + O2 (g). A) What will happen to [SO3] if the temperature is increased? (assume DH is negative) B) What will happen if the total pressure is doubled? 13. Write the correct form of the equilibrium constant expression for the reaction below? NH3 (aq) + H2O(l) NH4+ (aq) + OH- (aq) 14. We add 50.0 mL of 0.200 M NH3 (aq) to 50.0 mL of 0.010 M CuCl2 (aq). What will [Cu2+ ] be when equilibrium is reached? Cu2+(aq) + 4NH3(aq) [Cu(NH3)4]2+ (aq) K = 6.8 x 1012 15. Ammonium hydrogen sulfide decomposes on heating, NH4HS(s) NH3 (g) + H2S(g) Kp = 0.11 at 25 oC If we have a 1.00 L flask which already contains gaseous NH3 at a pressure of 0.25 atm and heat up some NH4HS, what will the equilibrium pressure of NH3 be? 16. Determine if the following system is at equilibrium, the reactant concentrations are too high, the product concentrations are too high, or if one simply cannot determine which with the information given. PCl5 (g) PCl3 (g) + Cl2 (g) Kp = 11.5 P(PCl5) = 1.15 atm P(PCl3) = 5.30 atm P(Cl2) = 2.80 atm 17. Which of the following is true about a chemical system at equilibrium? a. no reactions take place b. temperature increases will no longer increase reaction rates c. the rates of forward and reverse reactions are equal d. all reaction products will be solids 18. Relate the two equilibrium constants for the two reactions shown? NOCl(g) NO(g) + 1/2 Cl2 (g) K1 2 NO(g) + Cl2 (g) 2 NOCl(g) K2 19. We place 1.00g of [Ni(NH3)6]Cl2 into 100. mL of water and find that at equilibrium, [NH3] = 0.0452 M. Calculate K for the following reaction: [Ni(NH3)6]2+ Ni2+ (aq) + 6NH3 (aq) 20. We place an excess (more than can dissolve) of PbCl2 (s) into 100. mL of water and find that at equilibrium, [Cl-] = 0.032 M. Calculate K for the following reaction: PbCl2(s) Pb2+ (aq) + 2Cl- (aq) 21. We put 10.0 mg of AgCl in 50.0 mL of water at 25 oC. What is the chloride ion concentration in the solution? (Ksp of AgCl is 1.8 x 10-10) 22. When a saturated solution of Cr(OH)3 is formed, the concentration of Cr3+ is 1.26 x 10-8 M. What is the value of Ksp for Cr(OH)3 (s)? 23. Barium sulfite is poorly soluble in water. BaSO3 (s) Ba2+ (aq) + SO32- (aq) K sp = 8.0 x 10-7 What is DGo for the reaction at 25 oC? (R = 8.314510 J/K mol) 24. The following general reaction is not spontaneous at room temperature. A + B C + D DHo = +50.0 kJ and DSo = +100. J/K At what temperature will the reaction become spontaneous? 25. Predict the products of the following acid-base reaction. HCl(aq) + NaOH(aq) ? 26. The following reactants are mixed in equal molar portions. Predict if the resulting solution will be acidic, basic, neutral, or if there is not enough information given to tell for sure. H2SO4 (aq) + KOH(aq) ? 27. We mix 100. mL of 0.10 M HCl and 100. mL of 0.10 M NaCN. What is the pH of the resulting solution? Ka (HCN) = 4.0 x 10-10 28. We have 100. mL of 0.10 M HClO solution. What is the pH of the resulting solutions after 0, 10, 25, 50, and 60 mL of 0.20 M NaOH is added? pKa (HClO) = 7.46 29. We have 250. mL of a 0.20 M solution of NH4Cl. It has a pH = 4.97. If we add 10.0 mL of a 1.00 M NH3 solution, what will the pH be? Ka (NH4+) = 5.6 x 10-10 30. We have 100. mL of water. We add to this 0.50 g of NaCH3COO and 1.00 mL of 1.00 M CH3COOH. What is the pH of the resulting solution? Ka (CH3COOH) = 1.8 x 10-5 31. We have 100. mL of a 0.20 M solution of NaClO. How many milliliters of 0.10 M HClO should be added to make a buffer of pH = 7.2? Ka (HClO) = 3.5 x 10-8 32. We have 200. mL of a buffer solution containing 0.10 M CH3COOH and 0.10 M NaCH3COO. If we add 10.00 mL of 0.20 M NaOH to this solution, what will the resulting pH be? Ka (CH3COOH) = 1.8 x 10-5 uh)*ab klpqstuv{|   L                :LMSTVW^_   z {   H I } ~       A C F H I K } ~                    :/1dfpqvwjk)/@E                         8E$%+,BCmnopst cd  LM  FG                        9QRTU'(,-.:=yz                        9ABFGWYd       )*+s4`a:kl2DL%lt<A % p  N G & . X ` 2 M O 12lT\!)q$pcp QY[X EMO (*v]MU"$qy   MUrt BJij?G[cd0L dddd=/Bpretest Whitney KingSymbolTimesdd