Question 1

A lizard's metabolism slows down in cold weather because the chemical reactions in its body slow down. Which factor is primarily responsible for this change in reaction rate?

Accepted Answer

The temperature decreases, reducing the number of molecules with enough energy to overcome the activation barrier.

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 best describes the instantaneous rate of a reaction?

Accepted Answer

It is the rate measured at a specific moment, determined by the slope of the tangent to the concentration vs. time curve.

Question 4

A reaction is zero order with respect to reactant A. Which of the following is true?

Accepted Answer

The rate is independent of [A].

Question 5

The half-life of a first-order reaction is given by $$t_{1/2} = \frac{0.693}{k}. If $$the rate constant $$k is $$doubled, what happens to the half-life?

Accepted Answer

It is halved.

Question 6

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

Accepted Answer

Spectrophotometry

Question 7

The Arrhenius equation is $$k = Ae$$^{-E_a/(RT)}$$. What does the exponential factor e$$^{-E_a/(RT)}$$ represent?

Accepted Answer

The fraction of molecules with enough energy to overcome the activation barrier.

Question 8

A reaction has a rate law $$	ext{Rate} = k[	ext{A}]^1[	ext{B}]^2. If $$the concentration of A is doubled and B is tripled, by what factor does the rate increase?

Accepted Answer

18

Question 9

Which of the following statements about catalysts is correct?

Accepted Answer

A catalyst provides an alternative pathway with a lower activation energy.

Question 10

Which plot would yield a straight line for a first-order reaction?

Accepted Answer

$$\ln[A] vs$$. $$t$$

Question 11

For a reaction mechanism, which step determines the overall rate law?

Accepted Answer

The slowest (rate-determining) step

Question 12

Which of the following best explains why increasing temperature generally increases the rate of a chemical reaction?

Accepted Answer

It increases the fraction of molecules with enough energy to overcome the activation barrier.

Question 13

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

3

Question 14

Which of the following is a correct statement about reaction intermediates?

Accepted Answer

They are formed and consumed during the reaction mechanism.

Question 15

If a reaction has a half-life that depends on the initial concentration, which order is it most likely to be?

Accepted Answer

Zero or second order

Question 16

Which of the following is NOT a method for measuring the concentration of a reactant or product during a reaction?

Accepted Answer

Electrolysis

Question 17

The rate law for an elementary step $$A + B \rightarrow C is$$:

Accepted Answer

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

Question 18

Which of the following best describes the role of enzymes in biological systems?

Accepted Answer

They provide a specific orientation for reactants, lowering the activation energy.

Question 19

A reaction has a rate constant $$k$$ that increases when the temperature is raised. According to the Arrhenius equation, which parameter is most directly responsible for this increase?

Accepted Answer

The exponential factor $$e^{-E_a/(RT)}$$ increases.

Question 20

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

Accepted Answer

It is generally less than 1 for complex molecules.

Chapter 15: Chemical Kinetics – Study Notes

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