Question 1

Which of the following best describes an elementary reaction?

Accepted Answer

A reaction that occurs in a single step and whose rate law can be written directly from its stoichiometry.

Question 2

Given the elementary reaction $$\mathrm{NOCl(g) + Cl(g) \rightarrow NO(g) + Cl_2$(g)}$$, what is the correct rate law?

Accepted Answer

$$\mathrm{Rate = k[NOCl][Cl]}$$

Question 3

Which of the following statements about reaction intermediates is correct?

Accepted Answer

They are produced in one step and consumed in a later step of the mechanism.

Question 4

Consider the following two-step mechanism:
Step 1: $$\mathrm{O_3$(g) + NO_2$(g) \rightarrow NO_3$(g) + O_2$(g)} ($$slow)
Step 2: $$\mathrm{NO_3$(g) + NO_2$(g) \rightarrow N_2O_5(g)} ($$fast)
What is the rate law for the overall reaction?

Accepted Answer

$$\mathrm{Rate = k[O_3$][NO_2$]}$$

Question 5

Which of the following best describes the rate-determining step in a multistep reaction?

Accepted Answer

The slowest step in the reaction mechanism.

Question 6

A reaction mechanism has the following steps:
Step 1: $$\mathrm{Cl_2$(g) \rightleftharpoons 2Cl(g)} ($$fast)
Step 2: $$\mathrm{Cl(g) + $$CHCl_3$$(g) \rightarrow HCl(g) + $$CCl_3$$(g)} ($$slow)
Step 3: $$\mathrm{Cl(g) + $$CCl_3$$(g) \rightarrow $$CCl_4$$(g)} ($$fast)
What is the molecularity of step 2?

Accepted Answer

Bimolecular

Question 7

Which of the following is true about the rate law for a reaction with a fast equilibrium first step and a slow second step?

Accepted Answer

The rate law may involve non-integer reaction orders.

Question 8

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

It provides an alternative pathway with a lower activation energy.

Question 9

In the catalyzed decomposition of hydrogen peroxide ($$\mathrm{H_2O_2}) $$with bromide and acid, which species acts as an intermediate?

Accepted Answer

$$\mathrm{Br_2$(aq)}$$

Question 10

Which of the following is a correct statement about homogeneous and heterogeneous catalysts?

Accepted Answer

A homogeneous catalyst is in the same phase as the reactants.

Question 11

Which of the following best explains why termolecular elementary reactions are rare?

Accepted Answer

It is unlikely for three molecules to collide simultaneously with the correct orientation and energy.

Question 12

Consider the energy profile for a multi-step reaction. What does each peak (maximum) represent?

Accepted Answer

A transition state between two steps.

Question 13

Which of the following is a real-world example of a heterogeneous catalyst?

Accepted Answer

A platinum catalyst in a car's catalytic converter.

Question 14

Which of the following is the correct rate law for the elementary reaction $$\mathrm{A + B + C \rightarrow products}$$?

Accepted Answer

$$\mathrm{Rate = k[A][B][C]}$$

Question 15

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

Accepted Answer

Increasing the activation energy of the reaction.

Question 16

In the context of the ozone hole, what is the role of chlorine atoms ($$\mathrm{Cl}) in $$the upper atmosphere?

Accepted Answer

They act as catalysts in the decomposition of ozone ($$\mathrm{O_3$}).$$

Question 17

Which of the following best describes the 'lock and key' mechanism of enzyme catalysis?

Accepted Answer

The enzyme binds specifically to the substrate, lowering the activation energy.

Question 18

A reaction has the following energy profile: it has three maxima and two minima between reactant and product. How many elementary steps and intermediates are present?

Accepted Answer

Three elementary steps and two intermediates.

Question 19

Which of the following is a correct statement about the rate law for an elementary reaction?

Accepted Answer

It can be written directly from the stoichiometry of the reaction.

Question 20

In the Monsanto acetic acid process, what is the main advantage of using a catalyst?

Accepted Answer

It increases atom economy and yield while reducing waste.

Chemical Kinetics and Catalysis: Mechanisms, Rate Laws, and Energy Profiles

Study Guide - Practice Questions

Study Guide - Flashcards