1. What is the term for a sequence of elementary steps that describes the detailed process of a chemical reaction?
a) Reaction pathway
b) Reaction mechanism
c) Reaction coordinate
d) Rate law
Answer: b) Reaction mechanism
2. In a reaction mechanism, what is an intermediate?
a) A reactant that is consumed during the reaction
b) A product that is formed in the reaction
c) A substance that is neither a reactant nor a product but is formed and consumed during the reaction
d) The final product of the reaction
Answer: c) A substance that is neither a reactant nor a product but is formed and consumed during the reaction
3. What is the term for a step in a reaction mechanism that is the slowest and determines the overall reaction rate?
a) Rate-determining step
b) Fast step
c) Intermediate step
d) Equilibrium step
Answer: a) Rate-determining step
4. How does a catalyst affect the reaction mechanism?
a) It changes the overall reaction balance
b) It increases the activation energy of the reaction
c) It lowers the activation energy of the reaction and provides an alternative pathway
d) It decreases the concentration of reactants
Answer: c) It lowers the activation energy of the reaction and provides an alternative pathway
5. What is the term for a proposed series of steps that must occur for a reaction to proceed from reactants to products?
a) Reaction pathway
b) Reaction mechanism
c) Reaction order
d) Transition state
Answer: b) Reaction mechanism
6. In a reaction mechanism, what is a transition state?
a) The state of a reactant before the reaction begins
b) A high-energy, unstable state through which reactants must pass to form products
c) The state of the final product of the reaction
d) The equilibrium state of the reactants and products
Answer: b) A high-energy, unstable state through which reactants must pass to form products
7. What is the term for the species that is formed in one elementary step and consumed in a subsequent step?
a) Reactant
b) Intermediate
c) Catalyst
d) Product
Answer: b) Intermediate
8. Which of the following best describes the overall reaction rate when a reaction mechanism has multiple steps?
a) It is determined by the rate of the fastest step
b) It is determined by the rate of the slowest step
c) It is the average rate of all steps combined
d) It is not affected by the mechanism
Answer: b) It is determined by the rate of the slowest step
9. What does the term “elementary step” refer to in a reaction mechanism?
a) A step involving multiple molecules
b) A step that is the overall reaction
c) A single molecular event that occurs in the mechanism
d) A step that occurs at equilibrium
Answer: c) A single molecular event that occurs in the mechanism
10. How can the reaction mechanism be inferred from experimental data?
a) By measuring the total energy of the reaction
b) By analyzing the rates of reaction and the effect of different conditions
c) By observing the physical appearance of the reactants and products
d) By calculating the equilibrium constant
Answer: b) By analyzing the rates of reaction and the effect of different conditions
11. What is the term for a reaction that involves a sequence of two or more elementary steps?
a) Unimolecular reaction
b) Bimolecular reaction
c) Chain reaction
d) Complex reaction
Answer: d) Complex reaction
12. Which of the following statements is true about intermediates in a reaction mechanism?
a) They are present in the initial state and are consumed by the end of the reaction
b) They are always detectable in the final products
c) They are usually formed in the final step of the reaction
d) They are stable, long-lived species
Answer: a) They are present in the initial state and are consumed by the end of the reaction
13. What role does a catalyst play in the reaction mechanism?
a) It changes the equilibrium position of the reaction
b) It shifts the reaction to favor the products
c) It lowers the activation energy and speeds up the reaction
d) It increases the concentration of the reactants
Answer: c) It lowers the activation energy and speeds up the reaction
14. What is the term for the series of elementary steps that leads to the formation of the final product?
a) Reaction path
b) Reaction coordinate
c) Reaction mechanism
d) Rate law
Answer: a) Reaction path
15. What is the term for the highest energy state along the reaction path, which corresponds to the transition state?
a) Activation energy
b) Reaction intermediate
c) Transition state
d) Reactant state
Answer: c) Transition state
16. How is the rate-determining step identified in a reaction mechanism?
a) By its highest energy barrier
b) By its lowest energy barrier
c) By its rate constant
d) By its equilibrium constant
Answer: a) By its highest energy barrier
17. What is a key feature of a chain reaction mechanism?
a) It involves a single elementary step
b) It has a series of steps where each step generates a new reactant
c) It does not involve any intermediates
d) It is always an endothermic process
Answer: b) It has a series of steps where each step generates a new reactant
18. What does the term “reaction pathway” refer to?
a) The path taken by reactants to become products
b) The route by which intermediates are formed
c) The series of elementary steps from reactants to products
d) The final equilibrium state of the reaction
Answer: c) The series of elementary steps from reactants to products
19. What information does a reaction coordinate diagram provide?
a) The concentration of reactants and products at equilibrium
b) The time taken for the reaction to reach completion
c) The energy changes throughout the reaction mechanism
d) The temperature at which the reaction occurs
Answer: c) The energy changes throughout the reaction mechanism
20. Which of the following factors can affect the rate-determining step of a reaction?
a) Temperature
b) Pressure
c) Concentration of reactants
d) All of the above
Answer: d) All of the above
21. In a reaction mechanism, what is a “chain reaction”?
a) A reaction where intermediates are formed but not consumed
b) A reaction involving a single elementary step
c) A reaction where each step produces a new reactant that continues the chain
d) A reaction where all products are formed at once
Answer: c) A reaction where each step produces a new reactant that continues the chain
22. What term describes the process where a reactant forms a product in a series of steps, each with its own transition state?
a) Sequential reaction
b) Multi-step reaction
c) Single-step reaction
d) Isomeric reaction
Answer: b) Multi-step reaction
23. What is the main purpose of studying a reaction mechanism?
a) To determine the final product only
b) To understand the detailed process and rate of reaction
c) To find the equilibrium constant
d) To calculate the reaction yield
Answer: b) To understand the detailed process and rate of reaction
24. How does the presence of a catalyst affect the reaction mechanism?
a) It changes the products formed
b) It provides an alternative reaction pathway with a lower activation energy
c) It alters the reaction equilibrium
d) It increases the activation energy required
Answer: b) It provides an alternative reaction pathway with a lower activation energy
25. In a reaction mechanism, what is the role of the “slow step”?
a) It is the step that produces the most intermediate
b) It is the fastest step in the mechanism
c) It is the step that controls the overall reaction rate
d) It is the step with the lowest activation energy
Answer: c) It is the step that controls the overall reaction rate
26. What does a “reaction rate law” express?
a) The relationship between the concentration of reactants and the reaction rate
b) The energy changes during the reaction
c) The steps involved in the reaction mechanism
d) The temperature dependence of the reaction
Answer: a) The relationship between the concentration of reactants and the reaction rate
27. What term describes the step in a reaction mechanism where reactants are transformed into products?
a) Elementary step
b) Rate-determining step
c) Intermediate step
d) Chain step
Answer: a) Elementary step
28. What is a characteristic feature of a reaction mechanism involving a multi-step process?
a) The overall reaction is the sum of all elementary steps
b) The rate of the reaction is constant throughout all steps
c) The intermediate species are always present in the final product
d) The reaction does not proceed through any transition states
Answer: a) The overall reaction is the sum of all elementary steps
29. How can the experimental observation of reaction intermediates be useful in studying reaction mechanisms?
a) It helps determine the overall reaction equilibrium
b) It provides insight into the specific steps of the reaction mechanism
c) It measures the rate of the reaction
d) It calculates the final product yield
Answer: b) It provides insight into the specific steps of the reaction mechanism
30. What is the main goal of proposing a reaction mechanism?
a) To predict the color of the reaction
b) To understand the detailed sequence of events that occur during the reaction
c) To determine the volume of reactants used
d) To calculate the energy released
Answer: b) To understand the detailed sequence of events that occur during the reaction