Q: Given the reaction $2\text{NO}_2(g) \rightarrow 2\text{NO}(g) + \text{O}_2(g)$, which of the following is the correct rate law if the reaction is found to be second order with respect to $\text{NO}_2$?

$\text{Rate} = k[\text{NO}_2]^2$

Question 1

Which of the following statements best describes the difference between thermodynamics and kinetics in a chemical reaction?

Accepted Answer

Thermodynamics tells us if a reaction is product or reactant favored, while kinetics tells us how fast a reaction occurs.

Question 2

Given the reaction $2	ext{NO}_2(g) ightarrow 2	ext{NO}(g) + 	ext{O}_2(g)$, which of the following is the correct rate law if the reaction is found to be second order with respect to $	ext{NO}_2$?

Accepted Answer

$	ext{Rate} = k[	ext{NO}_2]^2$

Question 3

If the concentration of a reactant $[A]$ is doubled in a reaction and the rate increases by a factor of four, what is the order of the reaction with respect to $A$?

Accepted Answer

Second order

Question 4

Which integrated rate law would yield a straight line when plotting $\ln [A]$ versus time?

Accepted Answer

First order: $\ln [A]_t = -kt + \ln [A]_0$

Question 5

A reaction has a rate law $	ext{Rate} = k[O_3][NO]$. If the concentration of $O_3$ is doubled while $NO$ is kept constant, what happens to the rate?

Accepted Answer

The rate is doubled.

Question 6

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

Accepted Answer

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

Question 7

For a first-order reaction, what is the expression for the half-life ($t_{1/2}$)?

Accepted Answer

$t_{1/2} = \frac{\ln(2)}{k}$

Question 8

Which of the following is NOT a requirement for a successful collision according to collision theory?

Accepted Answer

Reactant molecules must be in the same phase.

Question 9

The Arrhenius equation is $k = Ae^{-E_a/RT}$. What does $E_a$ represent?

Accepted Answer

The activation energy of the reaction

Question 10

A reaction is found to be zero order with respect to $A$. Which of the following statements is true?

Accepted Answer

Doubling $[A]$ will have no effect on the rate.

Question 11

Which of the following is a valid criterion for a proposed reaction mechanism?

Accepted Answer

The sum of the elementary steps must equal the overall reaction, and the predicted rate law must match the experimental rate law.

Question 12

For the reaction $2	ext{NO}_2(g) ightarrow 2	ext{NO}(g) + 	ext{O}_2(g)$, the following data were collected:

Time (s): 0, 100, 200, 300
$[NO_2]$ (M): $1.00 	imes 10^{-2}$, $6.48 	imes 10^{-3}$, $4.79 	imes 10^{-3}$, $3.80 	imes 10^{-3}$

Which plot would yield a straight line if the reaction is second order with respect to $NO_2$?

Accepted Answer

$1/[NO_2]$ vs. time

Question 13

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

Accepted Answer

It increases the number of molecules with energy greater than the activation energy.

Question 14

A reaction mechanism contains the following steps:
1. $A + B \rightarrow C$ (slow)
2. $C + D \rightarrow E$ (fast)
What is the rate law for the overall reaction?

Accepted Answer

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

Question 15

Which of the following is true about reaction intermediates?

Accepted Answer

They are formed in one step and consumed in a subsequent step.

Question 16

A catalyst in a car’s catalytic converter is an example of which type of catalysis?

Accepted Answer

Heterogeneous catalysis

Question 17

If a reaction has a half-life that decreases as the initial concentration increases, what is the likely order of the reaction?

Accepted Answer

Second order

Question 18

Which of the following is the correct unit for the rate constant $k$ for a second-order reaction?

Accepted Answer

$	ext{M}^{-1}\cdot	ext{s}^{-1}$

Question 19

Which of the following statements about the rate-determining step in a reaction mechanism is correct?

Accepted Answer

It determines the overall rate law for the reaction.

Chapter 14: Chemical Kinetics – Study Guide

Study Guide - Practice Questions

Study Guide - Flashcards