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문제 56a
The decomposition of XY is second order in XY and has a rate constant of 7.02⨉10-3 M-1• s-1 at a certain temperature. a. What is the half-life for this reaction at an initial concentration of 0.100 M?
문제 57a
The half-life for the radioactive decay of U-238 is 4.5 billion years and is independent of initial concentration. How long will it take for 10% of the U-238 atoms in a sample of U-238 to decay?
문제 57b
The half-life for the radioactive decay of U-238 is 4.5 billion years and is independent of initial concentration. If a sample of U-238 initially contained 1.5⨉1018 atoms when the universe was formed 13.8 billion years ago, how many U-238 atoms does it contain today?
문제 58a
The half-life for the radioactive decay of C-14 is 5730 years and is independent of the initial concentration. How long does it take for 25% of the C-14 atoms in a sample of C-14 to decay?
문제 58b
The half-life for the radioactive decay of C-14 is 5730 years and is independent of the initial concentration. If a sample of C-14 initially contains 1.5 mmol of C-14, how many millimoles are left after 2255 years?
문제 59
The diagram shows the energy of a reaction as the reaction progresses. Label each blank box in the diagram.
a. reactants b. products c. activation energy (Ea) d. enthalpy of reaction (ΔHrxn)
문제 61
The activation energy of a reaction is 56.8 kJ/mol and the frequency factor is 1.5⨉1011/ s. Calculate the rate constant of the reaction at 25 °C.
- The rate constant of a reaction at 32 °C is 0.055 s⁻¹. If the frequency factor is 1.2 × 10¹³ s⁻¹, what is the activation barrier?
문제 62
문제 63
The rate constant (k) for a reaction was measured as a function of temperature. A plot of ln k versus 1/T (in K) is linear and has a slope of -7445 K. Calculate the activation energy for the reaction.
- The rate constant (k) for a reaction was measured as a function of temperature. A plot of ln k versus 1/T (in K) is linear and has a slope of -1.01 * 10^4 K. Calculate the activation energy for the reaction.
문제 64
문제 65
The data shown here were collected for the first-order reaction: N2O(g) → N2(g) + O(g) Use an Arrhenius plot to determine the activation barrier and frequency factor for the reaction.
Temperature (K) Rate Constant (1 , s)
800 3.24⨉10- 5
900 0.00214
1000 0.0614
1100 0.955
문제 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.
문제 67
문제 68
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)
310 0.00434
320 0.0140
330 0.0421
340 0.118
350 0.316
- 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?
문제 69
문제 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.
문제 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?
문제 71
- If a temperature increase from 20.0 °C to 35.0 °C triples the rate constant for a reaction, what is the value of the activation energy for the reaction?
문제 72
문제 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?
문제 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)
문제 75
Consider this overall reaction, which is experimentally observed to be second order in AB and zero order in C: AB + C → A + BC Is the following mechanism valid for this reaction? AB + AB →k1 AB2 + A Slow AB2 + C → k2 AB + BC Fast
- 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)
문제 76
문제 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?
문제 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.
문제 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?
문제 78
문제 78b
Consider this two-step mechanism for a reaction: NO2(g) + Cl2(g) → k1 ClNO2(g) + Cl g) Slow NO2(g) + Cl(g) →k2 ClNO2(g) Fast b. Identify the intermediates in the mechanism.
문제 79
Many heterogeneous catalysts are deposited on high-surfacearea supports. Why?
문제 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.