5 Written questions
5 Matching questions
- The specific rate constant, k, for a reaction is 0.44 s−1 at 298 K, and the activation energy is 245.kJ/mol. Calculate k at 398 K. (The universal gas constant = 8.314 J/mol•K.)
a. 2.71 × 1010 s−1
b. 6.17 × 1010 s−1
c. 1.03 × 1010 s−1
d. 8.32 × 108 s−1
e. 4.51 × 109 s−1
- The rate constant, k, for a first-order reaction is 1.36 × 103 s−1 at 90.°C and the activation energy is 78.4 kJ/mol. Calculate the rate constant for this reaction at 50.°C.
a. 60.4 s−1
b. 54.5 s−1
c. 23.8 s−1
d. 4.85 s−1
e. 1.78 × 103 s−1
- The gas phase reaction A + B → C has a reaction rate which is experimentally observed to follow the relationship rate = k[A]2[B]. Which one of the following would affect the value of the specific rate constant, k?
a. increasing the temperature
b. changing the concentration of A
c. changing the concentration of B
d. changing the concentration of C
e. all of these
- Which of the following statements concerning graphical methods for determining reaction order is false?
a. For a first-order reaction the plot of ln[A] vs. time gives a straight line.
b. For a first-order reaction the slope of the straight-line graph equals −ak.
c. For a second-order reaction the plot of [A]2 vs. time gives a straight line.
d. For a first-order reaction the intercept of the straight-line graph equals ln [A]0.
e. For a zero-order reaction the plot of [A] vs. time gives a straight line.
- 124 go to graph
- a go to graph
- b b. 54.5 s−1
- c a. increasing the temperature
- d a. 2.71 × 1010 s−1
- e c. For a second-order reaction the plot of [A]2 vs. time gives a straight line.
5 Multiple choice questions
- d. 52.9 kJ/mol
- e. k[A][B]2
- b. The specific rate constant for a zero-order reaction is independent of temperature.
- d. 1 and 2
- b. 0.00648 M
5 True/False questions
The oxidation of NO by O3 is first order in each of the reactants, and its rate constant is 1.5 × 107 M−1•s−1. If the concentrations of NO and O3 are each 5.0 × 10−7 M, what is the rate of oxidation of NO in M•s−1?
a. 3.8 × 10−6
b. 2.5 × 10−14
c. 7.5 × 10−7
e. 7.5 → a. 3.8 × 10−6
Which of the following statements about reaction mechanisms is false?
a. A reaction can have more than one possible mechanism.
b. A reaction mechanism must be consistent with the experimentally observed rate law.
c. The slowest step in the reaction mechanism is called the rate-determining step.
d. Reaction mechanisms involve complex reaction steps.
e. Reaction mechanisms are difficult to prove. → d. Reaction mechanisms involve complex reaction steps.
A catalyst ____.
a. is used up in a chemical reaction
b. changes the value of ΔG0 of the reaction
c. is always a solid
d. does not influence the reaction in any way
e. changes the activation energy of the reaction → e. changes the activation energy of the reaction
The reaction, A + 2B → B2 + A, proceeds by the following mechanism: (A is a catalyst.)
A + B → AB (slow)
AB + B → B2 + A (fast)
What is the rate law expression for this reaction?
a. Rate = k[A]
b. Rate = k[B]
c. Rate = k[A][B]
d. Rate = k[A][B]2
e. Rate = k[A]2[B] → c. Rate = k[A][B]
Rate data have been determined at a particular temperature for the overall reaction
2NO + 2H2 → Ν2 + 2H2O
in which all reactants and products are gases.
Trial Run Initial [NO] Initial [H2] Initial Rate (M•s−1)
1 0.10 M 0.20 M 0.0150
2 0.10 M 0.30 M 0.0225
3 0.20 M 0.20 M 0.0600
What would be the initial rate of the reaction if the initial molar concentration of NO = 0.30 M and the initial molar concentration of H2 = 0.10 M?
a. 0.068 M•s−1
b. 0.22 M•s−1
c. 0.022 M•s−1
d. 0.040 M•s−1
e. 0.10 M•s−1 → c. A larger negative value of ΔG0 causes a faster reaction rate