Question 1

Consider the reaction 2A + 2B + C → 2D + E
If the rate law for this reaction is Rate = k[A][B]2, what will be the effect on the rate if the concentrations of A, B and C are all doubled at the same time?

Accepted Answer

A)   The rate will increase by a factor of 2.
B)   The rate will increase by a factor of 4.
C)   The rate will increase by a factor of 6.
D)   The rate will increase by a factor of 8.
E)   More information is needed before this question can be answered. D

Question 2

Consider the general reaction 5Br-(aq) + BrO3-(aq) + 6H+(aq) → 3Br2(aq) + 3H2O(aq)
For this reaction, the rate when expressed as Δ[Br2]/Δt is the same as

Accepted Answer

A)   -Δ[H2O]/Δt
B)   3Δ[BrO3-]/Δt
C)   -5Δ[Br-]/Δt
D)   -0.6Δ[Br-]/Δt
E)   None of these choices are correct. D

Question 3

The decomposition of dinitrogen pentaoxide has an activation energy of 102 kJ/mol and ΔH°rxn = + 55 kJ/mol. What is the activation energy for the reverse reaction?

Accepted Answer

A)   27 kJ/mol
B)   47 kJ/mol
C)   55 kJ/mol
D)   102 kJ/mol
E)   More information is needed, since this is a Hess's law calculation. B

Question 4

Butadiene, C4H6 (used to make synthetic rubber and latex paints) reacts to C8H12 with a rate law of rate = 0.014 L/(mol·s) [C4H6]2. What will be the concentration of C4H6 after 3.0 hours if the initial concentration is 0.025 M?

Accepted Answer

A)   0.0052 M
B)   0.024 M
C)   43 M
D)   190 M
E)   0.0000 M

Question 5

What is the molecularity of the following elementary reaction? NH2Cl(aq) + OH- (aq) → NHCl- (aq) + H2O(l)

Accepted Answer

A)   Unimolecular
B)   Bimolecular
C)   Termolecular
D)   Tetramolecular
E)   Need to know the reaction order before molecularity can be determined.

Question 6

The units of the rate of reaction depend on the order of the reaction.

Accepted Answer

A) True 
 B)False

Question 7

A reaction has the following rate law: Rate = k[A][B]2
In experiment 1, the concentrations of A and B are both 0.10 mol L-1; in experiment 2, the concentrations are both 0.30 mol L-1. If the temperature stays constant, what is the value of the ratio, Rate(2)/Rate(1)?

Accepted Answer

A)   3.0
B)   6.0
C)   9.0
D)   18
E)   27

Question 8

The rate law cannot be predicted from the stoichiometry of a reaction.

Accepted Answer

A) True 
 B)False

Question 9

Ammonium cyanate (NH4CNO) reacts to form urea (NH2CONH2). At 65°C the rate constant, k, is 3.60 L mol-1s-1.What is the rate law for this reaction?

Accepted Answer

A)   Rate = 3.60 L mol-1s-1[NH4CNO]
B)   Rate = 3.60 L mol-1s-1 [NH4CNO]2
C)   Rate = 0.28 mol L-1s-1 [NH4CNO]
D)   Rate = 0.28 mol L-1s-1[NH4CNO]2
E)   Rate = 3.60 L mol-1s-1 [NH2CONH2]-1

Question 10

The rate of a reaction is determined by the rate of the fastest step in the mechanism.

Accepted Answer

A) True 
 B)False

Question 11

A reactant R is being consumed in a first-order reaction. What fraction of the initial R is consumed in 4.0 half-lives?

Accepted Answer

A)   0.94
B)   0.87
C)   0.75
D)   0.13
E)   0.063

Question 12

Consider the following mechanism for the oxidation of bromide ions by hydrogen peroxide in aqueous acid solution. H+ + H2O2  H2O+-OH (rapid equilibrium)
H2O+-OH + Br- → HOBr + H2O (slow)
HOBr + H+ + Br- → Br2 + H2O (fast)
What is the overall reaction equation for this process?

Accepted Answer

A)   2H2O+-OH + 2Br- → H2O2 + Br2 + 2H2O
B)   2H+ + 2Br- + H2O2 → Br2 + 2H2O
C)   2H+ + H2O2 + Br- + HOBr → H2O+-OH + Br2 + H2O
D)   H2O+-OH + Br- + H+ → Br2 + H2O
E)   None of these choices are correct.

Question 13

Sulfur trioxide can undergo decomposition according to the equation 2SO3 → 2SO2 + O2
For this reaction, rate = -0.5Δ[SO3 ]/Δt = k[SO3]2. If the reaction rate is 1.75 × 10-7 mol L-1 min-1 when the concentration of sulfur trioxide is 5.4 × 10-3 mol L-1, what is the value of the rate constant k?

Accepted Answer

A)   3.2 × 10-5 L mol-1 min-1
B)   1.6 × 10-5 L mol-1 min-1
C)   6.0 × 10-3 L mol-1 min-1
D)   3.0 × 10-3 L mol-1 min-1
E)   1.6 × 10-2 L mol-1 min-1

Question 14

2NOBr(g) → 2NO(g) + Br2(g) [NOBr](mol L-1) Rate (molL-1s-1)
0)0450 1.62 × 10-3
0)0310 7.69 × 10-4
0)0095 7.22 × 10-5
Based on the initial rate data above, what is the value of the rate constant?

Accepted Answer

A)   0.0360 L mol-1s-1
B)   0.800 L mol-1s-1
C)   1.25 L mol-1s-1
D)   27.8 L mol-1s-1
E)   0.0360 s-1

Question 15

A reaction has an activation energy of 195.0 kJ/mol. When the temperature is increased from 200°C to 220°C, the rate constant will increase by a factor of

Accepted Answer

A)   1.1.
B)   4.3 × 104.
C)   3.2.
D)   7.5.
E)   None of these choices are correct.

Question 16

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

Question 17

A catalyst lowers the activation energy but does not affect the mechanism of a reaction.

Accepted Answer

A) True 
 B)False

Question 18

Consider the following mechanism for the oxidation of bromide ions by hydrogen peroxide in aqueous acid solution. H+ + H2O2  H2O+-OH (rapid equilibrium)
H2O+-OH + Br- → HOBr + H2O (slow)
HOBr + H+ + Br- → Br2 + H2O (fast)
Which of the following rate laws is consistent with the mechanism?

Accepted Answer

A)   Rate = k[H2O2][H+]2[Br-]
B)   Rate = k[H2O+-OH][Br-]
C)   Rate = k[H2O2][H+][Br-]
D)   Rate = k[HOBr][H+][Br-][H2O2]
E)   Rate = k[Br-]

Question 19

When the reaction A → B + C is studied, a plot of ln[A]t vs. time gives a straight line with a negative slope. 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.

Question 20

Sucrose decomposes to fructose and glucose in acid solution. When ln [sucrose] is plotted vs. time, a straight line with slope of -0.208 hr-1 results. What is the rate law for the reaction?

Accepted Answer

A)   Rate = 0.208 hr-1 [sucrose]2
B)   Rate = 0.208 hr-1 [sucrose]
C)   Rate = 0.0433 hr [sucrose]2
D)   Rate = 0.0433 hr [sucrose]
E)   Rate = 0.208 mol L-1hr-1 [sucrose]0

Exam 16: Kinetics Rates and Mechanisms of Chemical Reactions

Consider the reaction 2A + 2B + C → 2D + E If the rate law for this reaction is Rate = k[A][B]², what will be the effect on the rate if the concentrations of A, B and C are all doubled at the same time?

Consider the general reaction 5Br^-(aq) + BrO₃^-(aq) + 6H⁺(aq) → 3Br₂(aq) + 3H₂O(aq) For this reaction, the rate when expressed as Δ[Br₂]/Δt is the same as

The decomposition of dinitrogen pentaoxide has an activation energy of 102 kJ/mol and ΔH°_rxn = + 55 kJ/mol. What is the activation energy for the reverse reaction?

Butadiene, C₄H₆ (used to make synthetic rubber and latex paints) reacts to C₈H₁₂ with a rate law of rate = 0.014 L/(mol·s) [C₄H₆]². What will be the concentration of C₄H₆ after 3.0 hours if the initial concentration is 0.025 M?

What is the molecularity of the following elementary reaction? NH₂Cl(aq) + OH_- (aq) → NHCl_- (aq) + H₂O(l)

The units of the rate of reaction depend on the order of the reaction.

A reaction has the following rate law: Rate = k[A][B]₂ In experiment 1, the concentrations of A and B are both 0.10 mol L^-1; in experiment 2, the concentrations are both 0.30 mol L^-1. If the temperature stays constant, what is the value of the ratio, Rate(2) /Rate(1) ?

The rate law cannot be predicted from the stoichiometry of a reaction.

Ammonium cyanate (NH₄CNO) reacts to form urea (NH₂CONH₂) . At 65°C the rate constant, k, is 3.60 L mol^-1s^-1.What is the rate law for this reaction?

The rate of a reaction is determined by the rate of the fastest step in the mechanism.

A reactant R is being consumed in a first-order reaction. What fraction of the initial R is consumed in 4.0 half-lives?

2NOBr(g) → 2NO(g) + Br₂(g) [NOBr](mol L^-1) Rate (molL^-1s^-1) 0) 0450 1.62 × 10^-3 0) 0310 7.69 × 10^-4 0) 0095 7.22 × 10^-5 Based on the initial rate data above, what is the value of the rate constant?

A reaction has an activation energy of 195.0 kJ/mol. When the temperature is increased from 200°C to 220°C, the rate constant will increase by a factor of

A catalyst lowers the activation energy but does not affect the mechanism of a reaction.

When the reaction A → B + C is studied, a plot of ln[A]_t vs. time gives a straight line with a negative slope. What is the order of the reaction?

Sucrose decomposes to fructose and glucose in acid solution. When ln [sucrose] is plotted vs. time, a straight line with slope of -0.208 hr^-1 results. What is the rate law for the reaction?

Exam 16: Kinetics Rates and Mechanisms of Chemical Reactions

Consider the reaction 2A + 2B + C → 2D + E If the rate law for this reaction is Rate = k[A][B]2, what will be the effect on the rate if the concentrations of A, B and C are all doubled at the same time?

Consider the general reaction 5Br-(aq) + BrO3-(aq) + 6H+(aq) → 3Br2(aq) + 3H2O(aq) For this reaction, the rate when expressed as Δ[Br2]/Δt is the same as

The decomposition of dinitrogen pentaoxide has an activation energy of 102 kJ/mol and ΔH°rxn = + 55 kJ/mol. What is the activation energy for the reverse reaction?

Butadiene, C4H6 (used to make synthetic rubber and latex paints) reacts to C8H12 with a rate law of rate = 0.014 L/(mol·s) [C4H6]2. What will be the concentration of C4H6 after 3.0 hours if the initial concentration is 0.025 M?

What is the molecularity of the following elementary reaction? NH2Cl(aq) + OH- (aq) → NHCl- (aq) + H2O(l)

The units of the rate of reaction depend on the order of the reaction.

A reaction has the following rate law: Rate = k[A][B]2 In experiment 1, the concentrations of A and B are both 0.10 mol L-1; in experiment 2, the concentrations are both 0.30 mol L-1. If the temperature stays constant, what is the value of the ratio, Rate(2) /Rate(1) ?

The rate law cannot be predicted from the stoichiometry of a reaction.

Ammonium cyanate (NH4CNO) reacts to form urea (NH2CONH2) . At 65°C the rate constant, k, is 3.60 L mol-1s-1.What is the rate law for this reaction?

The rate of a reaction is determined by the rate of the fastest step in the mechanism.

A reactant R is being consumed in a first-order reaction. What fraction of the initial R is consumed in 4.0 half-lives?

Consider the following mechanism for the oxidation of bromide ions by hydrogen peroxide in aqueous acid solution. H+ + H2O2 H2O+-OH (rapid equilibrium) H2O+-OH + Br- → HOBr + H2O (slow) HOBr + H+ + Br- → Br2 + H2O (fast) What is the overall reaction equation for this process?

Sulfur trioxide can undergo decomposition according to the equation 2SO3 → 2SO2 + O2 For this reaction, rate = -0.5Δ[SO3 ]/Δt = k[SO3]2. If the reaction rate is 1.75 × 10-7 mol L-1 min-1 when the concentration of sulfur trioxide is 5.4 × 10-3 mol L-1, what is the value of the rate constant k?

2NOBr(g) → 2NO(g) + Br2(g) [NOBr](mol L-1) Rate (molL-1s-1) 0) 0450 1.62 × 10-3 0) 0310 7.69 × 10-4 0) 0095 7.22 × 10-5 Based on the initial rate data above, what is the value of the rate constant?

A reaction has an activation energy of 195.0 kJ/mol. When the temperature is increased from 200°C to 220°C, the rate constant will increase by a factor of

A catalyst lowers the activation energy but does not affect the mechanism of a reaction.

Consider the following mechanism for the oxidation of bromide ions by hydrogen peroxide in aqueous acid solution. H+ + H2O2 H2O+-OH (rapid equilibrium) H2O+-OH + Br- → HOBr + H2O (slow) HOBr + H+ + Br- → Br2 + H2O (fast) Which of the following rate laws is consistent with the mechanism?

When the reaction A → B + C is studied, a plot of ln[A]t vs. time gives a straight line with a negative slope. What is the order of the reaction?

Sucrose decomposes to fructose and glucose in acid solution. When ln [sucrose] is plotted vs. time, a straight line with slope of -0.208 hr-1 results. What is the rate law for the reaction?

Consider the reaction 2A + 2B + C → 2D + E If the rate law for this reaction is Rate = k[A][B]², what will be the effect on the rate if the concentrations of A, B and C are all doubled at the same time?

Consider the general reaction 5Br^-(aq) + BrO₃^-(aq) + 6H⁺(aq) → 3Br₂(aq) + 3H₂O(aq) For this reaction, the rate when expressed as Δ[Br₂]/Δt is the same as

The decomposition of dinitrogen pentaoxide has an activation energy of 102 kJ/mol and ΔH°_rxn = + 55 kJ/mol. What is the activation energy for the reverse reaction?

Butadiene, C₄H₆ (used to make synthetic rubber and latex paints) reacts to C₈H₁₂ with a rate law of rate = 0.014 L/(mol·s) [C₄H₆]². What will be the concentration of C₄H₆ after 3.0 hours if the initial concentration is 0.025 M?

What is the molecularity of the following elementary reaction? NH₂Cl(aq) + OH_- (aq) → NHCl_- (aq) + H₂O(l)

A reaction has the following rate law: Rate = k[A][B]₂ In experiment 1, the concentrations of A and B are both 0.10 mol L^-1; in experiment 2, the concentrations are both 0.30 mol L^-1. If the temperature stays constant, what is the value of the ratio, Rate(2) /Rate(1) ?

Ammonium cyanate (NH₄CNO) reacts to form urea (NH₂CONH₂) . At 65°C the rate constant, k, is 3.60 L mol^-1s^-1.What is the rate law for this reaction?

2NOBr(g) → 2NO(g) + Br₂(g) [NOBr](mol L^-1) Rate (molL^-1s^-1) 0) 0450 1.62 × 10^-3 0) 0310 7.69 × 10^-4 0) 0095 7.22 × 10^-5 Based on the initial rate data above, what is the value of the rate constant?

When the reaction A → B + C is studied, a plot of ln[A]_t vs. time gives a straight line with a negative slope. What is the order of the reaction?

Sucrose decomposes to fructose and glucose in acid solution. When ln [sucrose] is plotted vs. time, a straight line with slope of -0.208 hr^-1 results. What is the rate law for the reaction?