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Problem 66
The tabulated data show the rate constant of a reaction measured at several different temperatures. Use an Arrhenius plot to determine the activation barrier and frequency factor for the reaction.
Temperature (K) Rate Constant (1 , s)
300 0.0134
310 0.0407
320 0.114
330 0.303
340 0.757
- The tabulated data were collected for the second-order reaction: Cl(g) + H2(g) → HCl(g) + H(g). Use an Arrhenius plot to determine the activation barrier and frequency factor for the reaction. Temperature (K) and Rate Constant (L/mol # s) are as follows: 90 K, 0.00357; 100 K, 0.0773; 110 K, 0.956; 120 K, 7.781.
Problem 67
- What is the value of the rate constant at 425 K for a reaction with rate constants of 0.0117/s at 400.0 K and 0.689/s at 450.0 K?
Problem 69
Problem 69a
A reaction has a rate constant of 0.0117/s at 400.0 K and 0.689/s at 450.0 K. a. Determine the activation barrier for the reaction.
Problem 70b
A reaction has a rate constant of 0.000122/s at 27 °C and 0.228/s at 77 °C. b. What is the value of the rate constant at 17 °C?
- If a temperature increase from 10.0 °C to 20.0 °C doubles the rate constant for a reaction, what is the value of the activation energy for the reaction?
Problem 71
Problem 73
Consider these two gas-phase reactions: a. AA(g) + BB(g) → 2 AB(g) b. AB(g) + CD(g) → AC(g) + BD(g) If the reactions have identical activation barriers and are carried out under the same conditions, which one would you expect to have the faster rate?
Problem 74
Which of these two reactions would you expect to have the smaller orientation factor? Explain. a. O(g) + N2(g) → NO( g) + N(g) b. NO(g) + Cl2(g) → NOCl( g) + Cl(g)
- Consider this overall reaction, which is experimentally observed to be second order in X and first order in Y: X + Y → XY. a. Does the reaction occur in a single step in which X and Y collide? b. Is this two-step mechanism valid? 2X →k1/k2 X2 (Fast) X2 + Y →k3 XY + X (Slow)
Problem 76
Problem 77a
Consider this three-step mechanism for a reaction:
Cl2 (g) k1⇌k2 2 Cl (g) Fast
Cl (g) + CHCl3 (g) →k3 HCl (g) + CCl3 (g) Slow
Cl (g) + CCl3 (g) →k4 CCl4 (g) Fast
a. What is the overall reaction?
Problem 77b
Consider this three-step mechanism for a reaction:
Cl2 (g) k1⇌k2 2 Cl (g) Fast
Cl (g) + CHCl3 (g) →k3 HCl (g) + CCl3 (g) Slow
Cl (g) + CCl3 (g) →k4 CCl4 (g) Fast
b. Identify the intermediates in the mechanism.
Problem 77c
Consider this three-step mechanism for a reaction:
Cl2 (g) k1⇌k2 2 Cl (g) Fast
Cl (g) + CHCl3 (g) →k3 HCl (g) + CCl3 (g) Slow
Cl (g) + CCl3 (g) →k4 CCl4 (g) Fast
c. What is the predicted rate law?
- Consider this two-step mechanism for a reaction: Step 1: NO2(g) + Cl2(g) → ClNO2(g) + Cl(g) Slow Step 2: NO2(g) + Cl(g) → ClNO2(g) Fast c. What is the predicted rate law? a. What is the overall reaction?
Problem 78
Problem 79
Many heterogeneous catalysts are deposited on high-surfacearea supports. Why?
Problem 80
Suppose that the reaction A¡products is exothermic and has an activation barrier of 75 kJ/mol. Sketch an energy diagram showing the energy of the reaction as a function of the progress of the reaction. Draw a second energy curve showing the effect of a catalyst.
- Suppose that a catalyst lowers the activation barrier of a reaction from 125 kJ/mol to 55 kJ/mol. By what factor would you expect the reaction rate to increase at 25 °C? (Assume that the frequency factors for the catalyzed and uncatalyzed reactions are identical.)
Problem 81
Problem 82
The activation barrier for the hydrolysis of sucrose into glucose and fructose is 108 kJ/mol. If an enzyme increases the rate of the hydrolysis reaction by a factor of 1 million, how much lower must the activation barrier be when sucrose is in the active site of the enzyme? (Assume that the frequency factors for the catalyzed and uncatalyzed reactions are identical and a temperature of 25 °C.)
- How long will it take for 90% of the CH3CN to convert to CH3NC at 500 °C given the tabulated data: Time (h) [CH3CN] (M) 0.0 1.000, 5.0 0.794, 10.0 0.631, 15.0 0.501, 20.0 0.398, 25.0 0.316?
Problem 83
Problem 83a
The tabulated data were collected for this reaction at 500 °C: CH3CN(g) → CH3NC( g) a. Determine the order of the reaction and the value of the rate constant at this temperature.
- What is the half-life for this reaction at the initial concentration?
Problem 84
Problem 84c
The tabulated data were collected for this reaction at a certain temperature: X2Y → 2 X + Y c. What is the concentration of X after 10.0 hours?
- Consider the reaction: A + B + C → D. The rate law for this reaction is: Rate = k [A][C]^2 [B]^1/2. Suppose the rate of the reaction at certain initial concentrations of A, B, and C is 0.0115 M/s. What is the rate of the reaction if the concentrations of A and C are doubled and the concentration of B is tripled?
Problem 85
- At 400 K, oxalic acid decomposes according to the reaction: H2C2O4(g) → CO2(g) + HCOOH(g). In three separate experiments, the initial pressure of oxalic acid and the final total pressure after 20,000 seconds are measured. Experiment: 1) PH2C2O4 at t = 0: 65.8, PTotal at t = 20,000 s: 94.6; 2) PH2C2O4 at t = 0: 92.1, PTotal at t = 20,000 s: 132; 3) PH2C2O4 at t = 0: 111, PTotal at t = 20,000 s: 160. Find the rate law of the reaction and its rate constant.
Problem 88
Problem 89
Dinitrogen pentoxide decomposes in the gas phase to form nitrogen dioxide and oxygen gas. The reaction is first order in dinitrogen pentoxide and has a half-life of 2.81 h at 25 °C. If a 1.5-L reaction vessel initially contains 745 torr of N2O5 at 25 °C, what partial pressure of O2 is present in the vessel after 215 minutes?
Problem 91
Iodine atoms combine to form I2 in liquid hexane solvent with a rate constant of 1.5⨉1010 L/mols. The reaction is second order in I. Since the reaction occurs so quickly, the only way to study the reaction is to create iodine atoms almost instantaneously, usually by photochemical decomposition of I2. Suppose a flash of light creates an initial [I] concentration of 0.0100 M. How long will it take for 95% of the newly created iodine atoms to recombine to form I2?
- Is the question asking for the mass of sucrose hydrolyzed when 2.55 L of a 0.150 M sucrose solution is allowed to react for 195 minutes, given that the hydrolysis of sucrose (C12H22O11) into glucose and fructose in acidic water has a rate constant of 1.8 * 10^-4 s^-1 at 25 °C and the reaction is first order in sucrose?
Problem 92
- The reaction AB(aq) → A(g) + B(g) is second order in AB and has a rate constant of 0.0118 M^-1 s^-1 at 25.0 °C. A reaction vessel initially contains 250.0 mL of 0.100 M AB that is allowed to react to form the gaseous product. The product is collected over water at 25.0 °C. How much time is required to produce 200.0 mL of the products at a barometric pressure of 755.1 mmHg? (The vapor pressure of water at this temperature is 23.8 mmHg.)
Problem 93
- The reaction 2 H2O2(aq) → 2 H2O(l) + O2(g) is first order in H2O2 and under certain conditions has a rate constant of 0.00752 s⁻¹ at 20.0 °C. A reaction vessel initially contains 150.0 mL of 30.0% H2O2 by mass solution (the density of the solution is 1.11 g/mL). The gaseous oxygen is collected over water at 20.0 °C as it forms. What volume of O2 forms in 85.0 seconds at a barometric pressure of 742.5 mmHg? (The vapor pressure of water at this temperature is 17.5 mmHg.)
Problem 94
Problem 95b
Consider this energy diagram:
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b. Label the reactants, products, and intermediates.
Problem 95c
Consider this energy diagram:
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c. Which step is rate limiting?