Chemistry

Raymond Chang 10th edition

Chapter 13

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Question 1

For the reaction 2A + B → C it is found that changing the concentration of A has no impact on the rate, but when B is doubled the rate doubles. The rate law is

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A) rate = k[A]2[B].

B) rate = k[A][B]2.

C) rate = k[B]2.

D) none of the above.

Question 2

If the activation energy of a reaction is decreased, the reaction rate will increase.

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A) True

B) False

Question 3

Which of the following is true?

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20% 20% 20%20%20%A) A catalyst is not consumed in the reaction.

B) A catalyst speeds up the forward reaction.

C) A catalyst speeds up the reverse reaction.

D) A catalyst decreases the activation energy.

E) All of the above.

Question 5

Which of the following will cause the reaction rate to increase?

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A) Increasing the temperature.

B) Adding a catalyst.

C) Reducing the concentration of reactants.

D) Both A and B.

E) Both B and C.

Question 6

Using the data below, determine the rate law for the reaction of A with B to produce C.

Exp 1: 0.100 M A, 0.100 M B, rate 0.120 M/s

Exp 2: 0.100 M A, 0.200 M B, rate 0.120 M/s

Exp 3: 0.200 M A, 0.100 M B, rate 0.480 M/s

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A) rate=k[A]2[B]

B) rate=k[A]2

C) rate=k[B]2

D) rate=k[A][B]

Question 8

If a proposed mechanism is consistent with the experimentally determined rate law, then the mechanism must be correct.

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A) True

B) False

Question 9

If a reaction is exothermic, then the activation energy for the forward reaction is __________ the activation energy for the reverse reaction.

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A) greater than

B) less than

C) equal to

D) none of the above--there is no relationship between the values

Question 10

Reactions rarely occur by mechanisms that include trimolecular elementary steps because

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A) the simultaneous collision of three molecules has a low probability.

B) simpler reaction mechanisms can always support the same rate law.

C) the math involved is too complicated.

D) all of the above.

Question 11

Which of the following can be used to determine the rate of a chemical reaction?

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A) Measuring a change in color

B) Measuring a change in mass

C) Measuring a change in concentration of a certain species

D) All of the above

E) None of the above

Question 12

The average rate of a reaction is the rate of reaction at any given time.

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A) True

B) False

Question 13

The rate of a reaction

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A) is always dependent of the concentration of the reactants.

B) may or may not depend on reactant concentration.

C) is never constant throughout a reaction.

D) can be calculated for first order and second order reactions only.

Question 15

In the reaction N2 + 3H2 → 2NH3, the rate of formation of ammonia at a given moment is 0.060 mol/s. What is the rate of reaction of hydrogen gas at the same moment?

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A) -0.060 mol/s

B) 0.090 mol/s

C) -0.090 mol/s

D) 0.040 mol/s

E) -0.040 mol/s

Question 16

The reaction C2H6 → 2CH3· is first order

with k = 2.50x10-3 s-1. How much time will be necessary for the concentration of C2H6 to decrease to 20 % of the initial

amount?

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A) 644 s

B) 280. s

C) 0.0025 s

D) 0.0005 s

E) None of the above

Question 17

The reaction C2H6 → 2CH3· is first order

with k = 2.5x10-3 s-1. Which of the following changes in concentration will last longer than the others?

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A) 2.0 M → 1.0 M

B) 1.0 M → 0.50 M

C) 0.50 M → 0.25 M

D) 0.80 M → 0.40 M

E) None of the above

Question 18

Which type of plot will be linear for a second order reaction?

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A) [A] vs time

B) ln[A] vs time

C) 1/[A] vs time

D) [A]2 vs time

E) None is linear

Question 20

A unimolecular reaction follows first order kinetics, and a bimolecular reaction follows second order kinetics.

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A) True

B) False

Answer Key – Chapter 13

1. D2. A3. E4. D5. D 6. B7. B8. B9. B 10. A

11. D12. B13. B14. C15. C 16. A17. A18. C19. C 20. B