Question 1

A lizard becomes lethargic when its body temperature drops. Which principle of chemical kinetics best explains this phenomenon?

Accepted Answer

The rate of chemical reactions decreases as temperature decreases, slowing down metabolic processes.

Question 2

For the reaction $$2	ext{NO}_2(g) ightarrow 2	ext{NO}(g) + 	ext{O}_2(g)$$, the rate law is found to be $$	ext{Rate} = k[	ext{NO}_2]^2. $$What happens to the rate if the concentration of $$	ext{NO}_2 is $$tripled?

Accepted Answer

The rate increases by a factor of 9.

Question 3

Which of the following experimental techniques would be most appropriate for continuously monitoring the progress of a reaction that produces a colored product?

Accepted Answer

Spectrophotometry

Question 4

A reaction is found to be first order in A and second order in B. What is the overall order of the reaction?

Accepted Answer

Third order

Question 5

The integrated rate law for a first-order reaction is $$\ln [A] = -kt + \ln [A]_0. $$What would a plot of $$\ln [A]$$ versus time look like for this reaction?

Accepted Answer

A straight line with a negative slope

Question 6

A reaction has a half-life that does not depend on the initial concentration of the reactant. What is the order of this reaction?

Accepted Answer

First order

Question 7

The Arrhenius equation is $$k = Ae$$^{-E_a/(RT)}$$. According to this equation, what will happen to the rate constant k$ if the activation energy E_a$ increases, assuming all other factors remain constant?

Accepted Answer

The rate constant $$k$$ will decrease.

Question 8

Which of the following best explains why reaction rates generally increase with increasing temperature?

Accepted Answer

A greater fraction of molecules have enough thermal energy to surmount the activation barrier.

Question 9

For a reaction with the rate law $$	ext{Rate} = k[A]^0$$, what will happen to the rate if the concentration of A is doubled?

Accepted Answer

The rate will remain the same.

Question 10

A catalyst increases the rate of a chemical reaction by:

Accepted Answer

Providing an alternative pathway with a lower activation energy.

Question 11

Which of the following statements about reaction mechanisms is correct?

Accepted Answer

The rate law for an elementary step can be deduced directly from its molecularity.

Question 12

For a second-order reaction, which of the following plots will yield a straight line?

Accepted Answer

$$1/[A]$$ versus time

Question 13

A decomposition reaction slows down as it proceeds, and its half-life depends on the initial concentration. Which statement is most likely true for this reaction?

Accepted Answer

A doubling of the initial concentration results in a quadrupling of the rate.

Question 14

Which of the following is NOT a method for determining the concentration of a reactant in a reaction mixture?

Accepted Answer

Electrolysis

Question 15

Which of the following best describes the role of an enzyme in a biological reaction?

Accepted Answer

It provides a specific orientation for the substrate, lowering the activation energy.

Question 16

If the rate law for a reaction is $$	ext{Rate} = k[A][B]^2$$, what is the effect on the rate if $$[A] is $$doubled and $$[B] is $$tripled?

Accepted Answer

The rate increases by a factor of 18.

Question 17

Which of the following statements about the collision theory of chemical reactions is correct?

Accepted Answer

Only collisions with sufficient energy and proper orientation result in a reaction.

Question 18

A reaction has the following mechanism:
Step 1 (slow): $$A + B \rightarrow C$$
Step 2 (fast): $$C + D \rightarrow E$$
What is the rate law for the overall reaction?

Accepted Answer

$$	ext{Rate} = k[A][B]$$

Question 19

Which of the following is true about the orientation factor in collision theory?

Accepted Answer

It is generally less than 1 for complex molecules.

Question 20

Which of the following best describes a reaction intermediate?

Accepted Answer

A substance that is formed in one step and consumed in a later step of a reaction mechanism.

Chapter 15: Chemical Kinetics – Study Notes

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