Wksht Rate Laws

Transcription

1 Wksht Rate Laws Iowa State University Leader: Deborah Course: CHEM 178 Instructor: Bonaccorsi/Vela Date: 1/16/18 1. Describe the difference between average rate and instantaneous rate. Average rate- change in concentration over time that rxn occurs Instantaneous rate- change in concentration at a specific time period/interval; differs at specific moments 2. Write the complete rate expression for aa + bb cd + dd + ff Rate = -(1 / a) (ΔA / Δt) = -(1 / b) (ΔB / Δt) = (1 / c) (ΔC / Δt) = etc.. 3. For the reaction C6H12O6 (s) + 6O2 (g) 6CO2 (g) + 6H2O (l) a. Balance it. b. The Rate Law is determined to be Rate = k[c6h12o6][o2] 2.What is the overall order of the reaction? 3 4. a. Derive the rate law using the following information and the reaction below: 2 HgCl2 (aq) + C2O4 2- (aq) 2 Cl - (aq) + 2 CO2 (g) + Hg2Cl2 (s) Experiment [HgCl2] (M) [C2O4 2- ] (M) Rate (M/s) * * * *10-5 Rate = k[hgcl2][c2o4 2- ] 2 b. What is the overall reaction order? 3 c. Calculate the rate constant for this reaction, with units. k = 8.7 x 10-3 M -2 s -1 d. What is the rate when M A and M B are present? 2.2 x 10-4 M/s 5. For the reaction 2A + B A2B find the rate law, units on the rate constant, and value of the rate constant Hixson-Lied Student Success Center

2 Rate = k[a] 2 [B] k = 0.8 M -2 s -1

3 Wksht 1.2 Integrated Rate Laws and Energetics Iowa State University Leader: Deborah Course: CHEM 178 Instructor: Bonaccorsi/Vela Date: 1/17/18 1. Explain how you experimentally determine which order a reaction is. a. First order reactions: ln[a] = straight line i. From graphing you learn ln[a]0 = y-intercept ii. Slope = -k iii. t = x-axis iv. y-axis = ln[a] b. Second order reactions: 1/[A] = straight line i. 1/[A] = y-axis ii. 1/[A]0 = y-intercept iii. k = slope iv. t = x-axis c. Zeroth order reactions: [A] = straight line 2. What is the order of this reaction based on the graphs? 2 nd order 3. What are the half-life equations for a. first-order reactions? t1/2 = / k b. second-order reactions? t1/2 = 1 / k[a]0 4. The half-life of Zn-71 is 2.4 minutes. If a sample had g at the beginning, how many grams would be left after 7.6 minutes has elapsed? 13.3 g 5. Os-182 has a half-life of 21.5 hours. How many grams of a 28.0 gram sample would have decayed after exactly three half-lives? 24.5 g 1060 Hixson-Lied Student Success Center

4 6. Rate = k[n2o5] a. At 45 C, the rate constant for the reaction with the rate law given above is 6.22 x 10-4 s -1. If the initial concentration of N2O5 in the solution is M, how long will it take for the concentration to drop to M, in minutes? 61.7 minutes b. If the initial concentration of N2O5 is M, what will the concentration be after exactly 1 hour? M 7. The following diagram shows a reaction profile. Label the components indicated by the boxes. (End-of-chapter question 14.9 in book) (1) Reactants (2) Ea (3) H or E (4) Products top of peak = transition state

5 Wksht 1.3 Integrated Rate Laws and Energetics Iowa State University Leader: Deborah Course: CHEM 178 Instructor: Miller Date: 9/3/17 1. The rate constant for the reaction H2(g) + I2(g) 2 HI(g) is 3.6 x 10-4 M -1 s -1 at 326 o C. At 468 o C the rate constant was found to be 2.8 x 10-2 M -1 s -1. Find the activation energy. Ea = = ~ 11.3 x 10-4 J/mol 2. What is the difference between the molecularities of a reaction? What are the 2 most common? the number of molecules of reactants involved in collision reactions; unimolecular & bimolecular 3. What is the difference between an intermediate compound and a catalyst? Intermediate: formed in one elementary reaction then consumed in another (product then reactant) Catalyst: a reactant in first step then product in later step(s) (reactant then product) 4. a. Which step of the above reaction profile is rate determining? 2 nd step b. How many intermediates are there? 2 c. How many transition states are they? 3 d. Which steps are endothermic? Which steps are exothermic? 2 nd step; 1 st and 3 rd steps 1060 Hixson-Lied Student Success Center

6 5. Find the rate law for the following reaction using the elementary steps. Rate = k[h2][no] 2 6. For the reaction, 2NO2(g) + F2(g) 2NO2F with a rate law = k[no2][f2]: a. Propose a series for a bimolecular elementary process. (1) NO2 + F2 NO2F + F Rate(1) = k1[no2][f2] (2) NO2 + F NO2F Rate(2) = k2[no2][f] 2 NO2 + F2 2 NO2F Rate = k[no2][f2] b. Identify which elementary process is the rate determinant and which one is the fast reaction. rate-determinant = step 1 fast reaction = step 2

7 Wksht 2.2(2) Chemical Equilibrium II Iowa State University Leader: Deborah Course: CHEM 178 Instructor: Bonaccorsi/Vela Date: 1/30/18 1. Write the correct Kc expression for the following reaction. C3H8 (g) + 5 O2 (g) 3 CO2 (g) + 4 H2O (g) Kc = ([CO2] 3 [H2O] 4 ) / ([C3H8][O2] 5 ) 2. Write an expression for the equilibrium constant of this reaction. N2O4 (g) + O3 (g) N2O5 (s) + O2 (g) **same format as question above, excluding any pure solids or liquids** 3. The equilibrium constant is 3.58 x 10 4 for the following reaction: A + B C + D Which of the following statements is true regarding this equilibrium? (select all that apply) a. The reaction is product favored. b. The reaction is reactant favored. c. Equilibrium lies far to the right. d. Equilibrium lies far to the left. e. None are true, as the concentration of reactants and products are comparable. 4. What is Kc for the reaction NO2 (g) + ClNO (g) ClNO2 (g) + NO (g) at 25 C, given the following information? Kc = [NO2][ClNO] / [ClNO2][NO] = 1.3 x 10 4 (at 25 C) Kc = 7.69 x What is Kc for the reaction 3 H2 (g) + 3 I2 (g) 6 HI (g) at 350 C when the equilibrium-constant value of H2 (g) + I2 (g) 2 HI (g) is 60 at the same temperature? Kc = 2.16 x Calculate K for the following reaction given the following equilibrium concentrations of H2, CO, and H2O. C (s) + H2O (g) CO (g) + H2 (g) K =??? Equilibrium concentrations (M): K = 5.63 x What is the equilibrium concentration of O2(g)? 2 SO2 (g) + O2 (g) 2 SO3 (g) K = 2.8 x 10 2 at 1000 K 1.3 x 10 2?? 0.25 [O2] = 1.32 x 10-8 M 8. Find the Kc for the reaction NO (g) + CO2 (g) NO2 (g) + CO (g). NO2 (g) + NO2 (g) NO3 (g) + NO (g) Kc = [NO3][NO] / [NO2] 2 = 7.38 x Hixson-Lied Student Success Center

8 NO3 (g) + CO (g) NO2 (g) + CO2 (g) Kc = [NO2][CO2] / [NO3][CO] = 6.45 x 10-5 Kc3 = 2.10 x 10 5

9 Wksht 2.3 Chemical Equilibrium III Iowa State University Leader: Deborah Course: CHEM 178 Instructor: Bonaccorsi/Vela Date: 1/31/18 1. D 2. Balance the following reaction then calculate K given the following equilibrium concentrations. Al (s) + MnSO4 (aq) Al2(SO4)3 (aq) + Mn (s) Equilibrium Concentrations (M): Kc = Consider the reaction PbCl2 (s) Pb 2+ (aq) + 2 Cl - (aq) with an equilibrium constant of 2.47x10-3. a. What is the value of K for the reverse reaction? Kc = 405 b. What is the value of K for 3 PbCl2 (s) 3 Pb 2+ (aq) + 6 Cl - (aq)? Kc = 1.51 x (1) AX (s) + B (g) A (s) + BX (g) Kp = 0.68 (2) AX (s) + Z2 (g) A (s) + XZ2 (g) Kp = 1.3 A mixture of B(g) and Z2(g) is added to a closed container of AX(s) and A(s). Find the equilibrium constant of the reaction B (g) + XZ2 (g) BX (g) + Z2 (g) when it s allowed to reach equilibrium. Kp = Hixson-Lied Student Success Center

10 [C] = 2.20 x 10-4 M 6. What s the difference between an equilibrium constant and a reaction quotient? K: ratio of products to reactants at equilibrium; only one value at each T Q: ratio of products to reactions at any point during a reaction; varies within T 7. Consider the reaction N2 (g) + 3H2 (g) 2NH3 (g) with a Kp of If a chamber has N2(g) at 1.00 atm, H2(g) 0.52 atm, and NH3(g) at atm, what reaction, if any, will occur? Equilibrium