Question 1

In the Arrhenius equation,the symbol A is called _____ and the symbol R is called _____.

Accepted Answer

A) ​Avogadro's number,Coulomb's constant 
B) ​Bohr's radius,gravitational constant 
C) ​bond length,atomic mass unit 
D) ​frequency factor,gas constant 
E) ​bond strength,neutron mass 
A) ​Avogadro's number,Coulomb's constant 
B) ​Bohr's radius,gravitational constant 
C) ​bond length,atomic mass unit 
D) ​frequency factor,gas constant 
E) ​bond strength,neutron mass

Question 2

One mechanism for the depletion of ozone in the stratosphere is proposed as follows:
Cl + O3 → ClO + O2
ClO + O → Cl + O2
Identify any catalysts and intermediates in the reaction.

Accepted Answer

A) Cl is a catalyst,there are no intermediates 
B) O is an intermediate,ClO is a catalyst 
C) O2 is a catalyst,O is an intermediate 
D) ClO is a catalyst,there are no intermediates 
E) Cl is a catalyst,ClO is an intermediate 
A) Cl is a catalyst,there are no intermediates 
B) O is an intermediate,ClO is a catalyst 
C) O2 is a catalyst,O is an intermediate 
D) ClO is a catalyst,there are no intermediates 
E) Cl is a catalyst,ClO is an intermediate

Question 3

A rate constant for a particular reaction is 0.0070 M-1·s−1.What is the overall order of this reaction?
​

Accepted Answer

A) 2 
B) 3 
C) 4 
D) 0 
E) 1 
A) 2 
B) 3 
C) 4 
D) 0 
E) 1

Question 4

A first-order chemical reaction is observed to have a rate constant of 24 min-1.What is the corresponding half-life for the reaction?

Accepted Answer

A) 1.7 s 
B) 1.7 min 
C) 35 min 
D) 2.5 s 
E) 34.3 s 
A) 1.7 s 
B) 1.7 min 
C) 35 min 
D) 2.5 s 
E) 34.3 s

Question 5

The rate constant for a reaction at 40.0°C is exactly 5 times that at 20.0°C.Calculate the Arrhenius energy of activation for the reaction.

Accepted Answer

A) 5.00 kJ/mol 
B) 7.38 kJ/mol 
C) 61.4 kJ/mol 
D) 13.4 kJ/mol 
E) none of these 
A) 5.00 kJ/mol 
B) 7.38 kJ/mol 
C) 61.4 kJ/mol 
D) 13.4 kJ/mol 
E) none of these

Question 6

The gas-phase decomposition of N2O5 is a first-order process with a rate constant of 1.50 × 10-3 s-1 at 55°C.The decomposition reaction is
N2O5(g)→ 2NO2(g)+  
O2(g)
If 8.0 g of N2O5 is placed in vessel 1 and 16.0 g of N2O5 in vessel 2 and the vessels are at the same temperature (55°C)and the same pressure,how much time is required for half of the N2O5 to decompose in each vessel?

Accepted Answer

A) Vessel 1 requires the same amount of time as vessel 2. 
B) Vessel 1 requires twice as much time as vessel 2. 
C) Vessel 1 requires three times as much time as vessel 2. 
D) Vessel 1 requires four times as much time as vessel 2. 
E) Vessel 2 requires twice as much time as vessel 1. 
A) Vessel 1 requires the same amount of time as vessel 2. 
B) Vessel 1 requires twice as much time as vessel 2. 
C) Vessel 1 requires three times as much time as vessel 2. 
D) Vessel 1 requires four times as much time as vessel 2. 
E) Vessel 2 requires twice as much time as vessel 1.

Question 7

Which of the following is not a postulate of collision theory?

Accepted Answer

A) Reactant molecules must collide to react. 
B) Reactant molecules must collide with a certain minimum energy in order to form products. 
C) Reactant molecules must collide with the correct orientation in order to form products. 
D) The rate constant is directly proportional to the energy of activation. 
E) The maximum in the potential energy curve,the activation energy,is determined by the structure of the activated complex or transition state. 
A) Reactant molecules must collide to react. 
B) Reactant molecules must collide with a certain minimum energy in order to form products. 
C) Reactant molecules must collide with the correct orientation in order to form products. 
D) The rate constant is directly proportional to the energy of activation. 
E) The maximum in the potential energy curve,the activation energy,is determined by the structure of the activated complex or transition state.

Question 8

The main reason for the increase in reaction rate with temperature is that

Accepted Answer

A) the fraction of high-energy molecules increases exponentially with temperature. 
B) the activation energy increases rapidly with temperature. 
C) a 10°C temperature rise results in the rate doubling. 
D) there is a dramatic increase in the number of collisions. 
E) heat acts as a catalyst. 
A) the fraction of high-energy molecules increases exponentially with temperature. 
B) the activation energy increases rapidly with temperature. 
C) a 10°C temperature rise results in the rate doubling. 
D) there is a dramatic increase in the number of collisions. 
E) heat acts as a catalyst.

Question 9

Which of the following statements concerning the experimental determination of reaction rates is incorrect?

Accepted Answer

A) To determine reaction rates one of the reactants must be colored. 
B) Monitoring changes in reactant or product physical properties is a convenient way to determine reaction rates. 
C) Analysis of samples withdrawn from the reaction solution at varying times is useful for slow reactions. 
D) Instrumental methods,such as visible spectroscopy,may be used to continuously measure changes in reactants or products. 
E) Any method of analysis that can determine product or reactant concentrations during the course of the reaction can potentially be used to determine reaction rates. 
A) To determine reaction rates one of the reactants must be colored. 
B) Monitoring changes in reactant or product physical properties is a convenient way to determine reaction rates. 
C) Analysis of samples withdrawn from the reaction solution at varying times is useful for slow reactions. 
D) Instrumental methods,such as visible spectroscopy,may be used to continuously measure changes in reactants or products. 
E) Any method of analysis that can determine product or reactant concentrations during the course of the reaction can potentially be used to determine reaction rates.

Question 10

The complete mechanism for a reaction is considered to occur in two steps,one of which is slow and the other fast:
A + 2B → C + D slow
A + C → E + F fast
What is the rate law predicted by this mechanism?

Accepted Answer

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

Question 11

Below is a proposed mechanism for the decomposition of H2O2.
H2O2 + I- → H2O + IO-
Slow
H2O2 + IO- → H2O + O2 + I-
Fast
Which of the following statements is incorrect?

Accepted Answer

A) IO- is a catalyst. 
B) I- is a catalyst. 
C) The net reaction is 2H2O2 → 2H2O + O2. 
D) The reaction is first-order with respect to [I-]. 
E) The reaction is first-order with respect to [H2O2]. 
A) IO- is a catalyst. 
B) I- is a catalyst. 
C) The net reaction is 2H2O2 → 2H2O + O2. 
D) The reaction is first-order with respect to [I-]. 
E) The reaction is first-order with respect to [H2O2].

Question 12

Which of the following statements is not a requirement for a valid reaction mechanism?

Accepted Answer

A) Each elementary reaction must be bimolecular. 
B) There must not be net production of any intermediates. 
C) The elementary reactions of a mechanism must add up to the net chemical reaction. 
D) A mechanism must have only one rate-determining step. 
E) The rate law predicted by a mechanism must agree with the experimental rate law. 
A) Each elementary reaction must be bimolecular. 
B) There must not be net production of any intermediates. 
C) The elementary reactions of a mechanism must add up to the net chemical reaction. 
D) A mechanism must have only one rate-determining step. 
E) The rate law predicted by a mechanism must agree with the experimental rate law.

Question 13

Two substances A and B react with each other in such a way that one-half of A remains after 25 min and one-fourth of A remains after 50 min.Doubling the concentration of B while keeping the concentration of A fixed doubles the rate of the reaction.This reaction is

Accepted Answer

A) first-order in both A and B. 
B) zero-order in both A and B. 
C) second-order in A and first-order in B. 
D) first-order in A and second-order in B. 
E) second-order in both A and B. 
A) first-order in both A and B. 
B) zero-order in both A and B. 
C) second-order in A and first-order in B. 
D) first-order in A and second-order in B. 
E) second-order in both A and B.

Question 14

Identify the Arrhenius equation from the following.

Accepted Answer

A) ​   
B) ​   
C) ​   
D) ​   
E) ​   
A) ​   
B) ​   
C) ​   
D) ​   
E) ​

Question 15

A second-order reaction starts with an initial concentration of 0.100 mol/L of the reactant.If the rate constant is 2.4× 10-2 L/(mol ∙ s),what is the time required to decrease the initial concentration to 0.050 mol/L?

Accepted Answer

A) 410 s 
B) 620 s 
C) 28.9 s 
D) 2.08 s 
E) 1200 s 
A) 410 s 
B) 620 s 
C) 28.9 s 
D) 2.08 s 
E) 1200 s

Question 16

A mechanism that explains the rate law,Rate = k[(CH3)3CO2C(CH3)3],for the gas-phase thermal decomposition of di-tert-butyl peroxide is given below.   For this proposed mechanism,the rate-determining step(s)must be

Accepted Answer

A) step 1. 
B) step 3. 
C) step 2. 
D) step 1 + step 2 + step 3. 
E) 2 times step 2. 
A) step 1. 
B) step 3. 
C) step 2. 
D) step 1 + step 2 + step 3. 
E) 2 times step 2.

Question 17

The rate constants for the first-order decomposition of a compound are 5.22× 10-4 s-1 at 43°C and 2.91 × 10-3 s-1 at 62°C.What is the value of the activation energy for this reaction? (R = 8.31 J/(mol · K))

Accepted Answer

A) 0.87104 kJ/mol 
B) 34.5 kJ/mol 
C) 0.751 kJ/mol 
D) 79.5 kJ/mol 
E) 2 kJ/mol 
A) 0.87104 kJ/mol 
B) 34.5 kJ/mol 
C) 0.751 kJ/mol 
D) 79.5 kJ/mol 
E) 2 kJ/mol

Question 18

Given the following fast equilibrium (below)proposed for the gas phase reaction between NO and O2,what is the expression for the equilibrium concentration of the intermediate NO3?
NO + O2  
NO3

Accepted Answer

A)    
B)    
C)    
D)    
E)    
A)    
B)    
C)    
D)    
E)

Question 19

If the rate law for a reaction is
Rate = k[ClO3-][I-][H+]2
What are the units of k when the unit of time is seconds and the unit of concentration is moles per liter?

Accepted Answer

A) (L ∙ s)/mol 
B) mol2/(L2 ∙ s) 
C) mol/(L ∙ s) 
D) L2/(mol2 ∙ s) 
E) L3/(mol3 ∙ s) 
A) (L ∙ s)/mol 
B) mol2/(L2 ∙ s) 
C) mol/(L ∙ s) 
D) L2/(mol2 ∙ s) 
E) L3/(mol3 ∙ s)

Question 20

The balanced chemical equation and rate law for the reaction between NO(g)and H2(g)at a particular temperature are
2NO(g)+ 2H2(g)→ N2(g)+ 2H2O(g)
Rate = k[NO]2[H2]
What is the reaction order with respect to nitric oxide?

Accepted Answer

A) 4 
B) 0 
C) 1 
D) 3 
E) 2 
A) 4 
B) 0 
C) 1 
D) 3 
E) 2

Exam 13: Rates of Reaction

In the Arrhenius equation,the symbol A is called _____ and the symbol R is called _____.

One mechanism for the depletion of ozone in the stratosphere is proposed as follows: Cl + O3 → ClO + O2 ClO + O → Cl + O2 Identify any catalysts and intermediates in the reaction.

A rate constant for a particular reaction is 0.0070 M-1·s−1.What is the overall order of this reaction? ​

A first-order chemical reaction is observed to have a rate constant of 24 min-1.What is the corresponding half-life for the reaction?

The rate constant for a reaction at 40.0°C is exactly 5 times that at 20.0°C.Calculate the Arrhenius energy of activation for the reaction.

Which of the following is not a postulate of collision theory?

The main reason for the increase in reaction rate with temperature is that

Which of the following statements concerning the experimental determination of reaction rates is incorrect?

The complete mechanism for a reaction is considered to occur in two steps,one of which is slow and the other fast: A + 2B → C + D slow A + C → E + F fast What is the rate law predicted by this mechanism?

Below is a proposed mechanism for the decomposition of H2O2. H2O2 + I- → H2O + IO- Slow H2O2 + IO- → H2O + O2 + I- Fast Which of the following statements is incorrect?

Which of the following statements is not a requirement for a valid reaction mechanism?

Two substances A and B react with each other in such a way that one-half of A remains after 25 min and one-fourth of A remains after 50 min.Doubling the concentration of B while keeping the concentration of A fixed doubles the rate of the reaction.This reaction is

Identify the Arrhenius equation from the following.

A second-order reaction starts with an initial concentration of 0.100 mol/L of the reactant.If the rate constant is 2.4× 10-2 L/(mol ∙ s),what is the time required to decrease the initial concentration to 0.050 mol/L?

A mechanism that explains the rate law,Rate = k[(CH3)3CO2C(CH3)3],for the gas-phase thermal decomposition of di-tert-butyl peroxide is given below. For this proposed mechanism,the rate-determining step(s)must be

The rate constants for the first-order decomposition of a compound are 5.22× 10-4 s-1 at 43°C and 2.91 × 10-3 s-1 at 62°C.What is the value of the activation energy for this reaction? (R = 8.31 J/(mol · K))

Given the following fast equilibrium (below)proposed for the gas phase reaction between NO and O2,what is the expression for the equilibrium concentration of the intermediate NO3? NO + O2 NO3

If the rate law for a reaction is Rate = k[ClO3-][I-][H+]2 What are the units of k when the unit of time is seconds and the unit of concentration is moles per liter?

The balanced chemical equation and rate law for the reaction between NO(g)and H2(g)at a particular temperature are 2NO(g)+ 2H2(g)→ N2(g)+ 2H2O(g) Rate = k[NO]2[H2] What is the reaction order with respect to nitric oxide?

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In the Arrhenius equation,the symbol A is called _ and the symbol R is called _.

One mechanism for the depletion of ozone in the stratosphere is proposed as follows: Cl + O₃ → ClO + O₂ ClO + O → Cl + O₂Identify any catalysts and intermediates in the reaction.

A rate constant for a particular reaction is 0.0070 M^-1·s−1.What is the overall order of this reaction?

A first-order chemical reaction is observed to have a rate constant of 24 min^-1.What is the corresponding half-life for the reaction?

Below is a proposed mechanism for the decomposition of H₂O₂. H₂O₂ + I^- → H₂O + IO^- Slow H₂O₂ + IO^- → H₂O + O₂ + I^- Fast Which of the following statements is incorrect?

A second-order reaction starts with an initial concentration of 0.100 mol/L of the reactant.If the rate constant is 2.4× 10^-2 L/(mol ∙ s),what is the time required to decrease the initial concentration to 0.050 mol/L?

A mechanism that explains the rate law,Rate = k[(CH₃)₃CO₂C(CH₃)₃],for the gas-phase thermal decomposition of di-tert-butyl peroxide is given below. For this proposed mechanism,the rate-determining step(s)must be

The rate constants for the first-order decomposition of a compound are 5.22× 10^-4 s^-1 at 43°C and 2.91 × 10^-3 s^-1 at 62°C.What is the value of the activation energy for this reaction? (R = 8.31 J/(mol · K))

Given the following fast equilibrium (below)proposed for the gas phase reaction between NO and O₂,what is the expression for the equilibrium concentration of the intermediate NO₃? NO + O₂ NO₃

If the rate law for a reaction is Rate = k[ClO₃^-][I^-][H⁺]² What are the units of k when the unit of time is seconds and the unit of concentration is moles per liter?

The balanced chemical equation and rate law for the reaction between NO(g)and H₂(g)at a particular temperature are 2NO(g)+ 2H₂(g)→ N₂(g)+ 2H₂O(g) Rate = k[NO]²[H₂] What is the reaction order with respect to nitric oxide?