Question 1

A reaction has a rate constant,k = 1.2 × 10-12 s-1 at 273 K and k = 5.1 × 10-7 s-1 at 373 K has an activation energy,Ea = ________ kJ/mol.

Accepted Answer

110

Question 2

Consider the first-order reaction A → B in which A molecules (shaded spheres)are converted to B molecules (unshaded spheres).  
-Which drawing (a)-(d)represents the reaction mixture at t = 2 minutes?

Accepted Answer

A) drawing (a) 
B) drawing (b) 
C) drawing (c) 
D) drawing (d) 
A) drawing (a) 
B) drawing (b) 
C) drawing (c) 
D) drawing (d) B

Question 3

What percentage of a radioactive substance remains after 7.00 half-lives have elapsed?

Accepted Answer

A) 0)391% 
B) 0)78% 
C) 1)56% 
D) 3)12% 
A) 0)391% 
B) 0)78% 
C) 1)56% 
D) 3)12% B

Question 4

The relative initial rates of the reaction AS1U1B12S1U1B0 + BS1U1B12S1U1B0 → products in vessels (a)-(d)are 1:1:4:4.Unshaded spheres represent AS1U1B12S1U1B0 molecules,and shaded spheres represent BS1U1B12S1U1B0 molecules present at the beginning of the reaction.  
-What is the order of reaction with respect to A2?

Accepted Answer

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

Question 5

A mechanism for a naturally occurring reaction that destroys ozone is:
Step 1: O3(g)+ HO(g)→ HO2(g)+ O2(g)
Step 2: HO2(g)+ O(g)→ HO(g)+ O2(g)
Which species is a catalyst?

Accepted Answer

A) HO 
B) HO2 
C) O 
D) O3 
A) HO 
B) HO2 
C) O 
D) O3

Question 6

For a reaction that follows the general rate law,Rate = k[A][B]2,what will happen to the rate of reaction if the concentration of B is increased by a factor of 2.00? The rate will

Accepted Answer

A) decrease by a factor of 1/4.00. 
B) decrease by a factor of 1/2.00. 
C) increase by a factor of 2.00. 
D) increase by a factor of 4.00. 
A) decrease by a factor of 1/4.00. 
B) decrease by a factor of 1/2.00. 
C) increase by a factor of 2.00. 
D) increase by a factor of 4.00.

Question 7

Consider a reaction that occurs by the following one-step mechanism:
AS1U1B12S1U1B0 + BS1U1B12S1U1B0 → 2 AB
The potential energy profile for this reaction is shown below.  
-The energy of reaction,ΔE,is given by the difference in energy between which two reaction stages?

Accepted Answer

A) reaction stage 2 - reaction stage 1 
B) reaction stage 2 - reaction stage 3 
C) reaction stage 1 - reaction stage 3 
D) reaction stage 3 - reaction stage 1 
A) reaction stage 2 - reaction stage 1 
B) reaction stage 2 - reaction stage 3 
C) reaction stage 1 - reaction stage 3 
D) reaction stage 3 - reaction stage 1

Question 8

If a sample of 233Pa takes 62.7 days to decrease to 20.0% of its original mass,what is its half-life?

Accepted Answer

A) 0)0370 days 
B) 27.0 days 
C) 157 days 
D) 195 days 
A) 0)0370 days 
B) 27.0 days 
C) 157 days 
D) 195 days

Question 9

Nitrogen dioxide decomposes at 300°C via a second-order process to produce nitrogen monoxide and oxygen according to the following chemical equation.
2 NO2(g)→ 2 NO(g)+ O2(g).
A sample of NO2(g)is initially placed in a 2.50-L reaction vessel at 300°C.If the half-life and the rate constant at 300°C are 11 seconds and 0.54 M-1 s-1,respectively,how many moles of NO2 were in the original sample?

Accepted Answer

A) 0)17 mol 
B) 0)42 mol 
C) 5)9 mol 
D) 15 mol 
A) 0)17 mol 
B) 0)42 mol 
C) 5)9 mol 
D) 15 mol

Question 10

The elementary reaction representing the formation of ozone:  
Is an example of a ________ reaction.

Accepted Answer

A) unimolecular 
B) bimolecular 
C) termolecular 
D) tetramolecular 
A) unimolecular 
B) bimolecular 
C) termolecular 
D) tetramolecular

Question 11

Consider a reaction that occurs by the following mechanism:
A + BC → AC + B
AC + D → A + CD
The potential energy profile for this reaction is shown below.  
-Intermediates occur at which reaction stages?

Accepted Answer

A) reaction stages 1 and 5 
B) reaction stages 2,3,and 4 
C) reaction stages 2 and 4 
D) reaction stage 3 
A) reaction stages 1 and 5 
B) reaction stages 2,3,and 4 
C) reaction stages 2 and 4 
D) reaction stage 3

Question 12

The reaction below is second order in ClO2 and first order in OH-.If the rate is expressed in M/s,the rate constant,k,has the units ________.
2 ClO2(aq)+ 2 OH-(aq)→ ClO3-(aq)+ ClO2-(aq)+ H2O(l)

Accepted Answer

Question 13

The decay constant,k,is given for each of the beta emitters below.Which one has the shortest half life?

Accepted Answer

A) (36Cl,7.09 × 10-24 s-1) 
B) (131I,9.94 × 10-7 s-1) 
C) (42K,1.55 × 10-5 s-1) 
D) (63Ni,2.39 × 10-10 s-1) 
A) (36Cl,7.09 × 10-24 s-1) 
B) (131I,9.94 × 10-7 s-1) 
C) (42K,1.55 × 10-5 s-1) 
D) (63Ni,2.39 × 10-10 s-1)

Question 14

Consider the first-order decomposition of A molecules (shaded spheres)in two vessels of equal volume.What is the half-life of decomposition in vessel (b)relative to the half-life of decomposition in vessel (a)?

Accepted Answer

A) half-life in vessel (b)/half-life in vessel (a)= 4:1 
B) half-life in vessel (b)/half-life in vessel (a)= 2:1 
C) half-life in vessel (b)/half-life in vessel (a)= 3:2 
D) half-life in vessel (b)/half-life in vessel (a)= 1:1 
A) half-life in vessel (b)/half-life in vessel (a)= 4:1 
B) half-life in vessel (b)/half-life in vessel (a)= 2:1 
C) half-life in vessel (b)/half-life in vessel (a)= 3:2 
D) half-life in vessel (b)/half-life in vessel (a)= 1:1

Question 15

A concentration-time study of the gas phase reaction 2 A3 → 3 A2 produced the data in the table below.
Time (s)[A3] (M)[A2] (M)
0 4)00 × 10-4 0
10 2.00 × 10-4 3.00 × 10-4
20 1.00 × 10-4 4.50 × 10-4
30 5.00 × 10-5 ?
What is the average rate of decomposition of A3 in the time interval 20-30 seconds?

Accepted Answer

A) 4)00 × 10-4 M/s 
B) 3)50 × 10-5 M/s 
C) 5)00 × 10-6 M/s 
D) 4)00 × 10-6 M/s 
A) 4)00 × 10-4 M/s 
B) 3)50 × 10-5 M/s 
C) 5)00 × 10-6 M/s 
D) 4)00 × 10-6 M/s

Question 16

When the concentration of A is doubled,the rate for the reaction: 2 A + B $\rarr$ 2 C quadruples.
When the concentration of B is doubled the rate remains the same.Which mechanism below is consistent with the experimental observations?

Accepted Answer

A) Step 1: A + B ? D (fast equilibrium) Step 2: A + D ? 2 C (slow) 
B) Step 1: A + B ? D (slow) Step 2: A + D ? 2 C (fast equilibrium) 
C) Step 1: 2 A ? D (slow) Step 2: B + D ? E (fast)
Step 3: E ? 2 C (fast) 
D) Step 1: 2 A ? D (fast equilibrium) Step 2: B + D ? E (slow)
Step 3: E ? 2 C (fast) 
A) Step 1: A + B ? D (fast equilibrium) Step 2: A + D ? 2 C (slow) 
B) Step 1: A + B ? D (slow) Step 2: A + D ? 2 C (fast equilibrium) 
C) Step 1: 2 A ? D (slow) Step 2: B + D ? E (fast)
Step 3: E ? 2 C (fast) 
D) Step 1: 2 A ? D (fast equilibrium) Step 2: B + D ? E (slow)
Step 3: E ? 2 C (fast)

Question 17

When the temperature of a gas whose activation energy is 55 kJ/mol is increased from 300 K to 320 K,the fraction of collisions with sufficient energy to react

Accepted Answer

A) decreases by a factor of 2. 
B) decreases by a factor of 4. 
C) increases by a factor of 2. 
D) increases by a factor of 4. 
A) decreases by a factor of 2. 
B) decreases by a factor of 4. 
C) increases by a factor of 2. 
D) increases by a factor of 4.

Question 18

A catalyst increases the rate of a reaction by providing a different reaction pathway that

Accepted Answer

A) lowers only the activation energy. 
B) lowers only the energy of the products. 
C) lowers only the energy of the reactants. 
D) All of these are affected by the presence of a catalyst. 
A) lowers only the activation energy. 
B) lowers only the energy of the products. 
C) lowers only the energy of the reactants. 
D) All of these are affected by the presence of a catalyst.

Question 19

Shown is a concentration versus time plot for a reaction involving gases A,B,and C.  
-Over the time interval 300 to 400 seconds,the rate of reaction with respect to A is Δ[A]/Δt =
3)7 × 10-5 M/s.Over the same time interval what is the rate of reaction with respect to C,Δ[C]/Δt?

Accepted Answer

A) Δ[C]/Δt = Δ[A]/Δt = 3.7 × 10-5 M/s 
B) Δ[C]/Δt = (1/4)(Δ[A]/Δt)= (1/4)(3.7 × 10-5 M/s)= 9.2 × 10-6 M/s 
C) Δ[C]/Δt = (1/2)(Δ[A]/Δt)= (1/2)(3.7 × 10-5 M/s)= 1.8 × 10-5 M/s 
D) Δ[C]/Δt = -(1/2)(Δ[A]/Δt)= -(1/2)(3.7 × 10-5 M/s)= -1.8 × 10-5 M/s 
A) Δ[C]/Δt = Δ[A]/Δt = 3.7 × 10-5 M/s 
B) Δ[C]/Δt = (1/4)(Δ[A]/Δt)= (1/4)(3.7 × 10-5 M/s)= 9.2 × 10-6 M/s 
C) Δ[C]/Δt = (1/2)(Δ[A]/Δt)= (1/2)(3.7 × 10-5 M/s)= 1.8 × 10-5 M/s 
D) Δ[C]/Δt = -(1/2)(Δ[A]/Δt)= -(1/2)(3.7 × 10-5 M/s)= -1.8 × 10-5 M/s

Question 20

What is the decay constant for a radioactive isotope which decreases to 34% of its original value in 2.48 hours?

Accepted Answer

A) 0)137 hr-1 
B) 0)168 hr-1 
C) 0)435 hr-1 
D) 2)30 hr-1 
A) 0)137 hr-1 
B) 0)168 hr-1 
C) 0)435 hr-1 
D) 2)30 hr-1

Exam 12: Chemical Kinetics

A reaction has a rate constant,k = 1.2 × 10-12 s-1 at 273 K and k = 5.1 × 10-7 s-1 at 373 K has an activation energy,Ea = ________ kJ/mol.

Consider the first-order reaction A → B in which A molecules (shaded spheres)are converted to B molecules (unshaded spheres). -Which drawing (a)-(d)represents the reaction mixture at t = 2 minutes?

What percentage of a radioactive substance remains after 7.00 half-lives have elapsed?

The relative initial rates of the reaction A2 + B2 → products in vessels (a)-(d)are 1:1:4:4.Unshaded spheres represent A2 molecules,and shaded spheres represent B2 molecules present at the beginning of the reaction. -What is the order of reaction with respect to A2?

A mechanism for a naturally occurring reaction that destroys ozone is: Step 1: O3(g)+ HO(g)→ HO2(g)+ O2(g) Step 2: HO2(g)+ O(g)→ HO(g)+ O2(g) Which species is a catalyst?

For a reaction that follows the general rate law,Rate = k[A][B]2,what will happen to the rate of reaction if the concentration of B is increased by a factor of 2.00? The rate will

Consider a reaction that occurs by the following one-step mechanism: A2 + B2 → 2 AB The potential energy profile for this reaction is shown below. -The energy of reaction,ΔE,is given by the difference in energy between which two reaction stages?

If a sample of 233Pa takes 62.7 days to decrease to 20.0% of its original mass,what is its half-life?

The elementary reaction representing the formation of ozone: Is an example of a ________ reaction.

Consider a reaction that occurs by the following mechanism: A + BC → AC + B AC + D → A + CD The potential energy profile for this reaction is shown below. -Intermediates occur at which reaction stages?

The reaction below is second order in ClO2 and first order in OH-.If the rate is expressed in M/s,the rate constant,k,has the units ________. 2 ClO2(aq)+ 2 OH-(aq)→ ClO3-(aq)+ ClO2-(aq)+ H2O(l)

The decay constant,k,is given for each of the beta emitters below.Which one has the shortest half life?

Consider the first-order decomposition of A molecules (shaded spheres)in two vessels of equal volume.What is the half-life of decomposition in vessel (b)relative to the half-life of decomposition in vessel (a)?

When the concentration of A is doubled,the rate for the reaction: 2 A + B →\rarr→ 2 C quadruples. When the concentration of B is doubled the rate remains the same.Which mechanism below is consistent with the experimental observations?

When the temperature of a gas whose activation energy is 55 kJ/mol is increased from 300 K to 320 K,the fraction of collisions with sufficient energy to react

A catalyst increases the rate of a reaction by providing a different reaction pathway that

Shown is a concentration versus time plot for a reaction involving gases A,B,and C. -Over the time interval 300 to 400 seconds,the rate of reaction with respect to A is Δ[A]/Δt = 3)7 × 10-5 M/s.Over the same time interval what is the rate of reaction with respect to C,Δ[C]/Δt?

What is the decay constant for a radioactive isotope which decreases to 34% of its original value in 2.48 hours?

Chemistry: Matter and Measurement

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Formulas, equations, and Moles

Reactions in Aqueous Solutions

Periodicity and the Atomic Structure of Atoms

Ionic Bonds and Some Main-Group Chemistry

Covalent Bonds and Molecular Structure

Thermochemistry: Chemical Energy

Gases: Their Properties and Behavior

Liquids,solids,and Phase Changes

Solutions and Their Properties

Chemical Equilibrium

Aqueous Equilibria: Acids and Bases

Applications of Aqueous Equilibria

Thermodynamics: Entropy, free Energy, and Equilibrium

Electrochemistry

Hydrogen, oxygen, and Water

The Main-Group Elements

Transition Elements and Coordination Chemistry

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A reaction has a rate constant,k = 1.2 × 10^-12 s^-1 at 273 K and k = 5.1 × 10^-7 s^-1 at 373 K has an activation energy,E_a = ________ kJ/mol.

The relative initial rates of the reaction A₂ + B₂ → products in vessels (a)-(d)are 1:1:4:4.Unshaded spheres represent A₂ molecules,and shaded spheres represent B₂ molecules present at the beginning of the reaction. -What is the order of reaction with respect to A₂?

A mechanism for a naturally occurring reaction that destroys ozone is: Step 1: O₃(g)+ HO(g)→ HO₂(g)+ O₂(g) Step 2: HO₂(g)+ O(g)→ HO(g)+ O₂(g) Which species is a catalyst?

For a reaction that follows the general rate law,Rate = k[A][B]²,what will happen to the rate of reaction if the concentration of B is increased by a factor of 2.00? The rate will

Consider a reaction that occurs by the following one-step mechanism: A₂ + B₂ → 2 AB The potential energy profile for this reaction is shown below. -The energy of reaction,ΔE,is given by the difference in energy between which two reaction stages?

If a sample of ²³³Pa takes 62.7 days to decrease to 20.0% of its original mass,what is its half-life?

The reaction below is second order in ClO₂ and first order in OH^-.If the rate is expressed in M/s,the rate constant,k,has the units ________. 2 ClO₂(aq)+ 2 OH^-(aq)→ ClO₃^-(aq)+ ClO₂^-(aq)+ H₂O(l)

When the concentration of A is doubled,the rate for the reaction: 2 A + B $\rarr$ 2 C quadruples. When the concentration of B is doubled the rate remains the same.Which mechanism below is consistent with the experimental observations?

Shown is a concentration versus time plot for a reaction involving gases A,B,and C. -Over the time interval 300 to 400 seconds,the rate of reaction with respect to A is Δ[A]/Δt = 3)7 × 10^-5 M/s.Over the same time interval what is the rate of reaction with respect to C,Δ[C]/Δt?