Question 1

Which of the following best explains why steel wool burns much more vigorously in pure oxygen than in air, as shown in the images?

Accepted Answer

The higher concentration of O$$_2 in $$pure oxygen increases the frequency of effective collisions, raising the reaction rate.

Question 2

Given the rate law $$	ext{Rate} = k[NO_2$]^2[CO]^0$$ for a reaction, what will happen to the rate if the concentration of CO is doubled while $$[NO_2$]$$ remains constant?

Accepted Answer

The rate will remain unchanged.

Question 3

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

Accepted Answer

18

Question 4

Which experimental technique would be most appropriate for monitoring the concentration of a colored reactant in solution over time?

Accepted Answer

Spectroscopy

Question 5

For a first-order reaction, which of the following plots yields a straight line?

Accepted Answer

$$\ln[A]$$ versus time

Question 6

A reaction is found to be second order in $$A. If $$the initial concentration of $$A is 0.50 M $$and the rate constant $$k is 0.20 M$^{-1}s$^{-1}$$, what is the initial rate?

Accepted Answer

0.05 M/s

Question 7

The half-life of a first-order reaction is given by $$t_{1/2} = \frac{0.693}{k}. If$$ $$k = 2.0 	imes 10$$^{-3}$$ s$$^{-1}$$, what is the half-life?

Accepted Answer

346.5 s

Question 8

Which of the following statements about the Arrhenius equation $$k = Ae$$^{-E_a/RT}$$ is correct?

Accepted Answer

A higher activation energy $$E_a$$ results in a smaller rate constant $$k at a $$given temperature.

Question 9

A reaction has an activation energy of 75 kJ/mol. If the temperature is increased, what happens to the fraction of molecules with enough energy to react?

Accepted Answer

It increases.

Question 10

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

Accepted Answer

It provides an alternative pathway with a lower activation energy.

Question 11

In a reaction mechanism, what is a reaction intermediate?

Accepted Answer

A species that is formed in one step and consumed in a subsequent step.

Question 12

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

Accepted Answer

2

Question 13

Which of the following is true for a zero-order reaction?

Accepted Answer

The rate is independent of the concentration of the reactant.

Question 14

A plot of $$1/[A]$$ versus time yields a straight line for a reaction. What is the order of the reaction with respect to $$A$$?

Accepted Answer

Second order

Question 15

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

Accepted Answer

It is the slowest step in the mechanism and determines the overall reaction rate.

Question 16

In the context of collision theory, which factor does NOT affect whether a collision between molecules leads to a reaction?

Accepted Answer

The color of the reactant molecules.

Question 17

A reaction has a rate constant $$k$$ that increases from 0.220 M$$^{-1}s$^{-1} at 650 K to 1.30 M$^{-1}s$^{-1} at 700 K. $$Which equation would you use to calculate the activation energy?

Accepted Answer

$$\ln \frac{k_2$}{k_1$} = \frac{E_a}{R} \left( \frac{1}{T_1$} - \frac{1}{T_2$} \right)$$

Question 18

Which of the following is a characteristic of a heterogeneous catalyst?

Accepted Answer

It is in a different phase than the reactants.

Question 19

In enzyme catalysis, what is the function of the active site?

Accepted Answer

It orients the substrate for reaction and lowers the activation energy.

Question 20

A reaction is monitored and the following data are obtained: $$[A] vs. $$time is linear with a negative slope. What is the order of the reaction?

Accepted Answer

Zero order

Chapter 15: Chemical Kinetics – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards