Question 1

Which statement best describes the role of a catalyst in a chemical reaction?

Accepted Answer

A catalyst provides an alternative pathway with lower activation energy, increasing the reaction rate.

Question 2

For the reaction $$2NO_2(g) + F_2$(g) ightarrow 2NO_2F(g)$$, the experimentally determined rate law is $$	ext{Rate} = k[NO_2$][F_2$]. $$What is the overall order of the reaction?

Accepted Answer

Second order

Question 3

Which of the following is true about reaction intermediates?

Accepted Answer

They are produced and consumed in different steps of the reaction mechanism.

Question 4

Given the following mechanism for the reaction of $$NO_2$$ with $$F_2$$:

$$NO_2$$ + $$F_2$$ \rightarrow NO_2F + F$$ (slow)
F$$ + $$NO_2$$ \rightarrow NO_2F$$ (fast)

Which species is a reaction intermediate?

Accepted Answer

$$F$$

Question 5

A reaction has a half-life that increases as the reaction proceeds. What is the most likely order of the reaction?

Accepted Answer

Second order

Question 6

The rate law for a reaction is $$	ext{Rate} = k[Q][R]^2. If$$ $$[R] is $$kept constant at $$2.0\,M$$ and $$[Q] is $$varied as $$0.0\,M$$, $$1.0\,M$$, and $$2.0\,M$$, what is the correct ranking of the reaction rates from lowest to highest?

Accepted Answer

Run 1 ($$[Q]=0.0$$) \u003c Run 2 ($$[Q]=1.0$$) \u003c Run 3 ($$[Q]=2.0)$$

Question 7

Which of the following best describes the rate-determining step (RDS) in a reaction mechanism?

Accepted Answer

It is the slowest step, and its rate law determines the overall reaction rate.

Question 8

For a first-order reaction, the half-life is given by $$t_{1/2} = \frac{0.693}{k}. If $$the rate constant $$k$$ for the decomposition of ammonium nitrite is $$3.0 	imes 10$$^{-3}$$\,s$$^{-1}$$, what is the half-life?

Accepted Answer

$$231\,s$$

Question 9

Which of the following is NOT a characteristic of an elementary reaction?

Accepted Answer

Its rate law must be determined experimentally.

Question 10

The Arrhenius equation relates the rate constant $$k to $$the activation energy $$E_a$$ and temperature $$T as$$ $$k = A e$$^{-E_a/(RT)}$$. If the activation energy decreases, what happens to the rate constant?

Accepted Answer

The rate constant increases.

Question 11

In the context of enzyme catalysis, which statement is correct?

Accepted Answer

Enzymes lower the activation energy for the reaction.

Question 12

For the reaction $$2NO(g) + O_2$(g) \rightarrow 2NO_2(g)$$, initial rate data are collected. If doubling $$[NO]$$ while keeping $$[O_2$]$$ constant quadruples the rate, what is the order with respect to $$NO$$?

Accepted Answer

Second order

Question 13

A catalyst is present at the beginning of a reaction, used in one step, and regenerated in a subsequent step. Why does it not appear in the overall reaction equation?

Accepted Answer

Because it is present in both reactants and products, so cancels out.

Question 14

In a real-world scenario, the rate law for tree growth is given as $$	ext{Rate} = (	ext{soil type})^a (	ext{temperature})^b (	ext{light})^c (	ext{fertilizer})^d. $$How would you determine the exponents $$a$$, $$b$$, $$c$$, and $$d$$?

Accepted Answer

By measuring the rate of growth while varying each factor independently in controlled experiments.

Question 15

If a person smoking two packs of cigarettes a day quadruples the rate of aging compared to a one-pack-a-day smoker, what is the exponent of the smoking term in the rate law?

Accepted Answer

2

Question 16

Which of the following is true about the molecularity of an elementary reaction?

Accepted Answer

It is the number of molecules involved in a single elementary step.

Question 17

For the reaction $$2Fe^{2+}(aq$$) + $$Cl_2(aq$$) \rightarrow $$2Fe^{3+}(aq) + 2Cl^-(aq$$)$$, if doubling $$[$$Fe^{2+}$$]$$ doubles the rate and doubling $$[$$Cl_2$$]$$ also doubles the rate, what is the overall order of the reaction?

Accepted Answer

Second order

Question 18

Which of the following is NOT a function of a catalyst?

Accepted Answer

Changing the equilibrium constant of the reaction.

Question 19

Which of the following best explains why enzymes are effective biological catalysts?

Accepted Answer

They provide a specific active site that stabilizes the transition state, lowering activation energy.

Chemical Kinetics: Transition State Theory, Reaction Mechanisms, and Catalysis

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