McMurry - Chemistry 8th Edition

Ch.14 - Chemical Kinetics

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McMurry 8th Edition

Ch.14 - Chemical Kinetics

Problem 117
Why doesn't a catalyst appear in the overall chemical equation for a reaction?
Problem 118
What distinguishes a catalyst from an intermediate?
Problem 119
Sulfur dioxide is oxidized to sulfur trioxide in the following sequence of reactions: 2 SO2(g) + 2 NO2(g) → 2 SO3(g) + 2 NO(g) 2 NO(g) + O2(g) → 2 NO2(g). (b) Identify any molecule that acts as a catalyst or intermediate in this reaction.
Problem 120
Consider the following mechanism for the decomposition of nitramide 1NH2NO22 in aqueous solution: NH2NO21aq2 + OH-1aq2S NHNO2 -1aq2 + H2O1l2 NHNO2 -1aq2S N2O1g2 + OH-1aq2 (c) How will the rate of the overall reaction be affected if HCl is added to the solution?
Problem 121
In Problem 14.113, you wrote a mechanism for the nitric oxide– facilitated decomposition of ozone. Does your mechanism involve a catalyst or a reaction intermediate? Explain.
Problem 122
The rate of the reaction A + B2 S AB + B is directly proportional to the concentration of B2, independent of the concentration of A, and directly proportional to the concentration of a substance C. (c) What is the role of C in this reaction? Why doesn't C appear in the chemical equation for the overall reaction?
Problem 123
The half-life of a typical peptide bond (the C–N bond in a protein backbone) in neutral aqueous solution is about 500 years. When a protease enzyme acts on a peptide bond, the bond’s half-life is about 0.010 s. Assuming that these half-lives correspond to first-order reactions, by what factor does the enzyme increase the rate of the peptide bond breaking reaction?
Problem 124
Consider the reaction H₂(g) + I₂(g) ⇌ 2 HI(g). The reaction of a fixed amount of H₂ and I₂ is studied in a cylinder fitted with a movable piston. Indicate the effect of each of the following changes on the rate of the reaction. (b) An increase in volume at constant temperature
Problem 124a
Consider the reaction H₂(g) + I₂(g) → 2 HI(g). The reaction of a fixed amount of H₂ and I₂ is studied in a cylinder fitted with a movable piston. Indicate the effect of each of the following changes on the rate of the reaction. (a) An increase in temperature at constant volume
Problem 124b
Consider the reaction H₂(g) + I₂(g) → 2 HI(g). The reaction of a fixed amount of H₂ and I₂ is studied in a cylinder fitted with a movable piston. Indicate the effect of each of the following changes on the rate of the reaction. (b) An increase in volume at constant temperature
Problem 124c
Consider the reaction H₂(g) + I₂(g) → 2 HI(g). The reaction of a fixed amount of H₂ and I₂ is studied in a cylinder fitted with a movable piston. Indicate the effect of each of the following changes on the rate of the reaction. (c) The addition of a catalyst
Problem 125
Concentration–time data for the conversion of A and B to D are listed in the following table. (c) What is the rate law?
Problem 126
Consider the following concentration–time data for the reaction of iodide ion and hypochlorite ion 1OCl-2. The products are chloride ion and hypoiodite ion 1OI-2. (c) Does the reaction occur by a single-step mechanism? Explain.
Problem 126a
Consider the following concentration–time data for the reaction of iodide ion and hypochlorite ion (OCl^-). The products are chloride ion and hypoiodite ion (OI^-).
(a) Write a balanced equation for the reaction.
Problem 126b
Consider the following concentration–time data for the reaction of iodide ion and hypochlorite ion (OCl^-). The products are chloride ion and hypoiodite ion (OI^-).
(b) Determine the rate law, and calculate the value of the rate constant.
Problem 126d
Consider the following concentration–time data for the reaction of iodide ion and hypochlorite ion (OCl^-). The products are chloride ion and hypoiodite ion (OI^-).
(d) Propose a mechanism that is consistent with the rate law, and express the rate constant in terms of the rate constants for the elementary steps in your mechanism. (Hint: Transfer of an H⁺ ion between H₂O and OCl^- is a rapid reversible reaction.)
Problem 127a
Consider the reversible, first-order interconversion of two molecules A and B: where k_f = 3.0⨉10-3 s^-1 is the rate constant for the forward reaction and kr = 1.0⨉10^-3 s^-1 is the rate constant for the reverse reaction. We'll see in Chapter 15 that a reaction does not go to completion but instead reaches a state of equilibrium with comparable concentrations of reactants and products if the rate constants k_f and k_r have comparable values.
(a) What are the rate laws for the forward and reverse reactions?
Problem 127b
Consider the reversible, first-order interconversion of two molecules A and B: where k_f = 3.0⨉10-3 s^-1 is the rate constant for the forward reaction and kr = 1.0⨉10^-3 s^-1 is the rate constant for the reverse reaction. We'll see in Chapter 15 that a reaction does not go to completion but instead reaches a state of equilibrium with comparable concentrations of reactants and products if the rate constants k_f and k_r have comparable values.
(b) Draw a qualitative graph that shows how the rates of the forward and reverse reactions vary with time.
Problem 127c
Consider the reversible, first-order interconversion of two molecules A and B: where k_f = 3.0⨉10-3 s^-1 is the rate constant for the forward reaction and kr = 1.0⨉10^-3 s^-1 is the rate constant for the reverse reaction. We'll see in Chapter 15 that a reaction does not go to completion but instead reaches a state of equilibrium with comparable concentrations of reactants and products if the rate constants k_f and k_r have comparable values.
(c) What are the relative concentrations of B and A when the rates of the forward and reverse reactions become equal?
Problem 128
Assume that you are studying the first-order conversion of a reactant X to products in a reaction vessel with a constant volume of 1.000 L. At 1 p.m., you start the reaction at 25 °C with 1.000 mol of X. At 2 p.m., you find that 0.600 mol of X remains, and you immediately increase the temperature of the reaction mixture to 35 °C. At 3 p.m., you discover that 0.200 mol of X is still present. You want to finish the reaction by 4 p.m. but need to continue it until only 0.010 mol of X remains, so you decide to increase the temperature once again. What is the minimum temperature required to convert all but 0.010 mol of X to products by 4 p.m.?
Problem 129
The half-life for the first-order decomposition of N2O4 is 1.3 * 10-5 s. N2O41g2S 2 NO21g2 If N2O4 is introduced into an evacuated flask at a pressure of 17.0 mm Hg, how many seconds are required for the pressure of NO2 to reach 1.3 mm Hg?
Problem 130a
Some reactions are so rapid that they are said to be diffusion-controlled; that is, the reactants react as quickly as they can collide. An example is the neutralization of H₃O⁺ by OH^-, which has a second-order rate constant of 1.3⨉10¹¹ M^-1 s^-1 at 25 °C. (a) If equal volumes of 2.0 M HCl and 2.0 M NaOH are mixed instantaneously, how much time is required for 99.999% of the acid to be neutralized?
Problem 130b
Some reactions are so rapid that they are said to be diffusion-controlled; that is, the reactants react as quickly as they can collide. An example is the neutralization of H₃O⁺ by OH^-, which has a second-order rate constant of 1.3⨉10¹¹ M^-1 s^-1 at 25 °C. (b) Under normal laboratory conditions, would you expect the rate of the acid–base neutralization to be limited by the rate of the reaction or by the speed of mixing?
Problem 131
The reaction 2 NO1g2 + O21g2S 2 NO21g2 has the thirdorder rate law rate = k3NO423O24, where k = 25 M-2 s-1. Under the condition that 3NO4 = 2 3O24, the integrated rate law is 13O242 = 8 kt +113O24022 What are the concentrations of NO, O2, and NO2 after 100.0 s if the initial concentrations are 3NO4 = 0.0200 M and 3O24 = 0.0100 M?
Problem 132
Consider the following data for the gas-phase decomposition of NO2: 2 NO2(g) → 2 NO(g) + O2(g)
If 0.0050 mol of NO2 is introduced into a 1.0 L flask and allowed to decompose at 650 K, how many seconds does it take for the NO2 concentration to drop to 0.0010 M?
Problem 133
Use the following initial rate data to determine the activation energy (in kJ/mol) for the reaction A + B ⇌ C.
Problem 134
The following experimental data were obtained in a study of the reaction 2 HI1g2S H21g2 + I21g2. Predict the concentration of HI that would give a rate of 1.0 * 10-5 M>s at 650 K.

Problem 136

The reaction AS C is first order in the reactant A and is known to go to completion. The product C is colored and absorbs light strongly at 550 nm, while the reactant and intermediates are colorless. A solution of A was prepared, and the absorbance of C at 550 nm was measured as a function of time. (Note that the absorbance of C is directly proportional to its concentration.) Use the following data to determine the half-life of the reaction.

Problem 137a

Values of E_a = 6.3 kJ/mol and A = 6.0⨉10⁸/(M s) have been measured for the bimolecular reaction: NO(g) + F₂(g) → NOF(g) + F(g) (a) Calculate the rate constant at 25 °C.

Problem 137d

Values of E_a = 6.3 kJ/mol and A = 6.0⨉10⁸/(M s) have been measured for the bimolecular reaction: NO(g) + F₂(g) → NOF(g) + F(g) (d) Why does the reaction have such a low activation energy?

Problem 117

Problem 118

Problem 119

Problem 120

Problem 121

Problem 122

Problem 123

Problem 124

Problem 124a

Problem 124b

Problem 124c

Problem 125

Problem 126

Problem 126a

Problem 126b

Problem 126d

Problem 127a

Problem 127b

Problem 127c

Problem 128

Problem 129

Problem 130a

Problem 130b

Problem 131

Problem 132

Problem 133

Problem 134

Problem 136

Problem 137a

Problem 137d