Question 1

In the lock and key model of enzyme action, the active site on the enzyme provides an exact fit for the substrate.

Accepted Answer

A) True 
 B)False

Question 2

The rate law for the reaction 3A → 2B is rate = k[A] with a rate constant of 0.0447 hr-1. What is the half-life of the reaction?

Accepted Answer

A)  0.0224 hr 
B)  0.0645 hr 
C)  15.5 hr 
D)  22.4 hr 
E)  44.7 hr 
A)  0.0224 hr 
B)  0.0645 hr 
C)  15.5 hr 
D)  22.4 hr 
E)  44.7 hr

Question 3

In an exothermic reaction,

Accepted Answer

A)  the forward reaction is slower than the reverse reaction. 
B)  the reaction rate will speed up with time. 
C)  the collision energy of the reactants will be greater than that of the products. 
D)  the forward reaction will have a lower activation energy than the reverse reaction. 
E)  the activation energy will change as the reaction progresses. 
A)  the forward reaction is slower than the reverse reaction. 
B)  the reaction rate will speed up with time. 
C)  the collision energy of the reactants will be greater than that of the products. 
D)  the forward reaction will have a lower activation energy than the reverse reaction. 
E)  the activation energy will change as the reaction progresses.

Question 4

The rate law for the rearrangement of CH3NC to CH3CN at 800 K is Rate = (1300 s-1)[CH3NC]. What is the half-life for this reaction?

Accepted Answer

A)  7.69 × 10-4 s 
B)  5.3 × 10-4 s 
C)  1.9 × 10-3 s 
D)  520 s 
E)  1920 s 
A)  7.69 × 10-4 s 
B)  5.3 × 10-4 s 
C)  1.9 × 10-3 s 
D)  520 s 
E)  1920 s

Question 5

The rate law for the reaction 3A → C is Rate = 4.36 × 10-2 L mol-1 hr-1 [A]2
What is the half-life for the reaction if the initial concentration of A is 0.250 M?

Accepted Answer

A)  0.0109 hr 
B)  0.0629 hr 
C)  15.9 hr 
D)  23.9 hr 
E)  91.7 hr 
A)  0.0109 hr 
B)  0.0629 hr 
C)  15.9 hr 
D)  23.9 hr 
E)  91.7 hr

Question 6

The decomposition of hydrogen peroxide is a first-order process with a rate constant of 1.06 × 10-3 min-1. How long will it take for the concentration of H2O2 to drop from 0.0200 M to 0.0120 M?

Accepted Answer

A)  < 1 min 
B)  7.55 min 
C)  481 min 
D)  4550 min 
E)  31,400 min 
A)  < 1 min 
B)  7.55 min 
C)  481 min 
D)  4550 min 
E)  31,400 min

Question 7

For the reaction A(g) + 2B(g) → 2C(g) + 2D(g)
The following data were collected at constant temperature. Determine the correct rate law for this reaction.
Trial Initial [A] Initial [B] Initial Rate
(mol/L) (mol/L) (mol/(L·min))
1 0)125 0.200 7.25
2 0)375 0.200 21.75
3 0)250 0.400 14.50
4 0)375 0.400 21.75

Accepted Answer

A)  Rate = k[A] [B] 
B)  Rate = k[A]2 [B] 
C)  Rate = k[A] [B]2 
D)  Rate = k[A] 
E)  Rate = k[A]3 
A)  Rate = k[A] [B] 
B)  Rate = k[A]2 [B] 
C)  Rate = k[A] [B]2 
D)  Rate = k[A] 
E)  Rate = k[A]3

Question 8

The half-life of a second-order reaction does not depend on the initial concentration of reactant.

Accepted Answer

A) True 
 B)False

Question 9

A boiled egg can be cooked at 100.0°C in exactly 5 minutes. At an altitude of around 2000 m where the boiling point of water is 93.0°C, it takes exactly 7.5 minutes to cook the egg to the same amount. What is the activation energy for the reaction involved when an egg is boiled?

Accepted Answer

A)  0.5 kJ/mol 
B)  4.5 kJ/mol 
C)  7.9 kJ/mol 
D)  66 kJ/mol 
E)  >100 kJ/mol 
A)  0.5 kJ/mol 
B)  4.5 kJ/mol 
C)  7.9 kJ/mol 
D)  66 kJ/mol 
E)  >100 kJ/mol

Question 10

Reaction intermediates differ from activated complexes in that

Accepted Answer

A)  they are stable molecules with normal bonds and are frequently isolated. 
B)  they are molecules with normal bonds rather than partial bonds and can occasionally be isolated. 
C)  they are intermediate structures which have characteristics of both reactants and products. 
D)  they are unstable and can never be isolated. 
E)  all reactions involve reaction intermediates, but not all have activated complexes. 
A)  they are stable molecules with normal bonds and are frequently isolated. 
B)  they are molecules with normal bonds rather than partial bonds and can occasionally be isolated. 
C)  they are intermediate structures which have characteristics of both reactants and products. 
D)  they are unstable and can never be isolated. 
E)  all reactions involve reaction intermediates, but not all have activated complexes.

Question 11

The rate constant for the reaction 3A → 4B is 6.00 × 10-3 L mol-1min-1. How long will it take the concentration of A to drop from 0.75 M to 0.25 M?

Accepted Answer

A)  2.2 × 10-3 min 
B)  5.5 × 10-3 min 
C)  180 min 
D)  440 min 
E)  5.0 × 102 min 
A)  2.2 × 10-3 min 
B)  5.5 × 10-3 min 
C)  180 min 
D)  440 min 
E)  5.0 × 102 min

Question 12

Carbon-14 is a radioactive isotope which decays with a half-life of 5730 years. What is the first-order rate constant for its decay, in units of years-1?

Accepted Answer

A)  5.25 × 10-5 years-1 
B)  1.21 × 10-4 years-1 
C)  1.75 × 10-4 years-1 
D)  3.49 × 10-4 years-1 
E)  3.97 × 103 years-1 
A)  5.25 × 10-5 years-1 
B)  1.21 × 10-4 years-1 
C)  1.75 × 10-4 years-1 
D)  3.49 × 10-4 years-1 
E)  3.97 × 103 years-1

Question 13

Dinitrogen tetraoxide, N2O4, decomposes to nitrogen dioxide, NO2, in a first-order process. If k = 2.5 × 103 s-1 at -5°C and k = 3.5 × 104 s-1 at 25°C, what is the activation energy for the decomposition?

Accepted Answer

A)  0.73 kJ/mol 
B)  58 kJ/mol 
C)  140 kJ/mol 
D)  580 kJ/mol 
E)  > 1000 kJ/mol 
A)  0.73 kJ/mol 
B)  58 kJ/mol 
C)  140 kJ/mol 
D)  580 kJ/mol 
E)  > 1000 kJ/mol

Question 14

Sulfuryl chloride, SO2Cl2(g), decomposes at high temperature to form SO2(g) and Cl2(g). The rate constant at a certain temperature is 4.68 × 10-5s-1. What is the order of the reaction?

Accepted Answer

A)  Zero 
B)  First 
C)  Second 
D)  Third 
E)  More information is needed to determine the order. 
A)  Zero 
B)  First 
C)  Second 
D)  Third 
E)  More information is needed to determine the order.

Question 15

A study of the decomposition reaction 3RS2 → 3R + 6S yields the following initial rate data. [RS2](mol L-1) Rate (mol/(L·s))
0)150 0.0394
0)250 0.109
0)350 0.214
0)500 0.438
What is the rate constant for the reaction?

Accepted Answer

A)  0.0103 L mol-1s-1 
B)  0.263 L mol-1s-1 
C)  0.571 L mol-1s-1 
D)  1.17 L mol-1s-1 
E)  1.75 L mol-1s-1 
A)  0.0103 L mol-1s-1 
B)  0.263 L mol-1s-1 
C)  0.571 L mol-1s-1 
D)  1.17 L mol-1s-1 
E)  1.75 L mol-1s-1

Question 16

All second-order reactions are bimolecular reactions.

Accepted Answer

A) True 
 B)False

Question 17

An increase in temperature increases the reaction rate because

Accepted Answer

A)  a greater fraction of the collisions have the correct orientation of molecules. 
B)  the activation energy of the reaction will increase. 
C)  the activation energy of the reaction will decrease. 
D)  temperature acts as a catalyst in chemical reactions. 
E)  more collisions will have enough energy to exceed the activation energy. 
A)  a greater fraction of the collisions have the correct orientation of molecules. 
B)  the activation energy of the reaction will increase. 
C)  the activation energy of the reaction will decrease. 
D)  temperature acts as a catalyst in chemical reactions. 
E)  more collisions will have enough energy to exceed the activation energy.

Question 18

The greater the energy of activation, Ea, the faster will be the reaction.

Accepted Answer

A) True 
 B)False

Question 19

In a reversible reaction, a catalyst will speed up the forward reaction but not affect the reverse reaction.

Accepted Answer

A) True 
 B)False

Question 20

All bimolecular reactions are second-order reactions.

Accepted Answer

A) True 
 B)False

Exam 16: Kinetics Rates and Mechanisms of Chemical Reactions

In the lock and key model of enzyme action, the active site on the enzyme provides an exact fit for the substrate.

The rate law for the reaction 3A → 2B is rate = k[A] with a rate constant of 0.0447 hr-1. What is the half-life of the reaction?

In an exothermic reaction,

The rate law for the rearrangement of CH3NC to CH3CN at 800 K is Rate = (1300 s-1)[CH3NC]. What is the half-life for this reaction?

The rate law for the reaction 3A → C is Rate = 4.36 × 10-2 L mol-1 hr-1 [A]2 What is the half-life for the reaction if the initial concentration of A is 0.250 M?

The decomposition of hydrogen peroxide is a first-order process with a rate constant of 1.06 × 10-3 min-1. How long will it take for the concentration of H2O2 to drop from 0.0200 M to 0.0120 M?

The half-life of a second-order reaction does not depend on the initial concentration of reactant.

A boiled egg can be cooked at 100.0°C in exactly 5 minutes. At an altitude of around 2000 m where the boiling point of water is 93.0°C, it takes exactly 7.5 minutes to cook the egg to the same amount. What is the activation energy for the reaction involved when an egg is boiled?

Reaction intermediates differ from activated complexes in that

The rate constant for the reaction 3A → 4B is 6.00 × 10-3 L mol-1min-1. How long will it take the concentration of A to drop from 0.75 M to 0.25 M?

Carbon-14 is a radioactive isotope which decays with a half-life of 5730 years. What is the first-order rate constant for its decay, in units of years-1?

Dinitrogen tetraoxide, N2O4, decomposes to nitrogen dioxide, NO2, in a first-order process. If k = 2.5 × 103 s-1 at -5°C and k = 3.5 × 104 s-1 at 25°C, what is the activation energy for the decomposition?

Sulfuryl chloride, SO2Cl2(g), decomposes at high temperature to form SO2(g) and Cl2(g). The rate constant at a certain temperature is 4.68 × 10-5s-1. What is the order of the reaction?

A study of the decomposition reaction 3RS2 → 3R + 6S yields the following initial rate data. [RS2](mol L-1) Rate (mol/(L·s)) 0)150 0.0394 0)250 0.109 0)350 0.214 0)500 0.438 What is the rate constant for the reaction?

All second-order reactions are bimolecular reactions.

An increase in temperature increases the reaction rate because

The greater the energy of activation, Ea, the faster will be the reaction.

In a reversible reaction, a catalyst will speed up the forward reaction but not affect the reverse reaction.

All bimolecular reactions are second-order reactions.

Keys to Studying Chemistry Definitions, Units, and Problem Solving

The Components of Matter

Stoichiometry of Formulas and Equations

Three Major Classes of Chemical Reactions

Gases and the Kinetic-Molecular Theory

Thermochemistry Energy Flow and Chemical Change

Quantum Theory and Atomic Structure

Electron Configuration and Chemical Periodicity

Models of Chemical Bonding

The Shapes of Molecules

Theories of Covalent Bonding

Intermolecular Forces Liquids, Solids, and Phase Changes

The Properties of Mixtures Solutions and Colloids

Periodic Patterns in the Main-Group Elements

Organic Compounds and the Atomic Properties of Carbon

Equilibrium the Extent of Chemical Reactions

Acid-Base Equilibria

Ionic Equilibria in Aqueous Systems

Thermodynamics Entropy, Free Energy, and Reaction Direction

Electrochemistry Chemical Change and Electrical Work

The Elements in Nature and Industry

Transition Elements and Their Coordination Compounds

Nuclear Reactions and Their Applications

Filters

The rate law for the reaction 3A → 2B is rate = k[A] with a rate constant of 0.0447 hr^-1. What is the half-life of the reaction?

The rate law for the rearrangement of CH₃NC to CH₃CN at 800 K is Rate = (1300 s^-1)[CH₃NC]. What is the half-life for this reaction?

The rate law for the reaction 3A → C is Rate = 4.36 × 10^-2 L mol^-1 hr^-1 [A]² What is the half-life for the reaction if the initial concentration of A is 0.250 M?

The decomposition of hydrogen peroxide is a first-order process with a rate constant of 1.06 × 10^-3 min^-1. How long will it take for the concentration of H₂O₂ to drop from 0.0200 M to 0.0120 M?

The rate constant for the reaction 3A → 4B is 6.00 × 10^-3 L mol^-1min^-1. How long will it take the concentration of A to drop from 0.75 M to 0.25 M?

Dinitrogen tetraoxide, N₂O₄, decomposes to nitrogen dioxide, NO₂, in a first-order process. If k = 2.5 × 10³ s^-1 at -5°C and k = 3.5 × 10⁴ s^-1 at 25°C, what is the activation energy for the decomposition?

Sulfuryl chloride, SO₂Cl₂(g), decomposes at high temperature to form SO₂(g) and Cl₂(g). The rate constant at a certain temperature is 4.68 × 10^-⁵s^-1. What is the order of the reaction?

A study of the decomposition reaction 3RS₂ → 3R + 6S yields the following initial rate data. [RS₂](mol L^-1) Rate (mol/(L·s)) 0)150 0.0394 0)250 0.109 0)350 0.214 0)500 0.438 What is the rate constant for the reaction?