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Chapter 6

Topic: Enthalpy

Section 6.1

Difficulty Level: Medium

  1. Estimate the enthalpy change of the following reaction under standard conditions.

Ans: +8 kJ/mol

Topic: Enthalpy

Section 6.1

Difficulty Level: Medium

  1. Estimate the enthalpy change of the following reaction under standard conditions.

Ans: +29 kJ/mol

Topic: Enthalpy

Section 6.1

Difficulty Level: Medium

  1. Estimate the enthalpy change of the following reaction under standard conditions.

Ans: -8 kJ/mol

Topic: Enthalpy

Section 6.1

Difficulty Level: Easy

  1. Which of the following is the enthalpy change of the following reaction under standard conditions?

A. -8 kJ/mol

B. +8 kJ/mol

C. +222 kJ/mol

D. +79 kJ/mol

Ans: B

Topic: Enthalpy

Section 6.1

Difficulty Level: Medium

  1. Which of the following is the enthalpy change of the following reaction under standard conditions?

A. -8 kJ/mol

B. +8 kJ/mol

C. -506 kJ/mol

D. +63 kJ/mol

Ans: A

Topic: Enthalpy

Section 6.1

Difficulty Level: Medium

  1. Later in the course, we will compare the halogenation of differently substituted carbons, comparing reactions like the ones below. Which of the following statements is true about reactions A and B?

A. Both reactions have a positive heat of reaction (Ho)

B. Neither reaction has a positive heat of reaction (Ho)

C. Only reaction A has a positive heat of reaction (Ho)

D. Only reaction B has a positive heat of reaction (Ho)

Ans: B

Topic: Enthalpy

Section 6.1

Difficulty Level: Medium

  1. Later in the course, we will compare the halogenation of differently substituted carbons, comparing reactions like the ones below. Which of the following reactions has a more exothermic heat of reaction (Ho)?

A. Reaction A has a more exothermic heat of reaction (Ho)

B. Reaction B has a more exothermic heat of reaction (Ho)

C. Both reactions have the same heat of reaction (Ho)

Ans: B

Topic: Enthalpy

Section 6.1

Difficulty Level: Hard

  1. You are working in a research laboratory and have developed a new reagent that cleaves C-H bonds homolytically. Unfortunately, this reagent can achieve only one of the transformations shown below. In light of bond dissociation energies, which transformation is most likely to be achieved?

Ans: A

Topic: Enthalpy

Section 6.1

Difficulty Level: Easy

  1. What type of bond cleavage does the following reaction involve?

A. homolytic

B. heterolytic

Ans: A

Topic: Enthalpy

Section 6.1

Difficulty Level: Easy

  1. What type of bond cleavage does the following reaction involve?

Ans: heterolytic

Topic: Entropy

Section 6.2

Difficulty Level: Easy

  1. Predict the sign of S of the following reaction.

A. positive

B. negative

C. no change

Ans: B

Topic: Entropy

Section 6.2

Difficulty Level: Easy

  1. Predict the sign of S of the following reaction.

A. positive

B. negative

C. no change

Ans: A

Topic: Entropy

Section 6.2

Difficulty Level: Easy

  1. Predict the sign of S of the following reaction.

A. positive

B. negative

C. no change

Ans: B

Topic: Entropy

Section 6.2

Difficulty Level: Medium

  1. Predict the sign of S of the following reaction.

Ans: positive

Topic: Entropy

Section 6.2

Difficulty Level: Medium

  1. Predict the sign of S of the following reaction.

Ans: negative

Topic: Entropy

Section 6.2

Difficulty Level: Hard

  1. Why is the entropy change negative for ring closures?

A. Closing a ring results in fewer molecules.

B. Closing a ring results in more molecules.

C. Closing a ring releases energy.

D. Closing a ring restricts the rotation around individual carbon-carbon bonds.

Ans: D

Topic: Entropy

Section 6.2

Difficulty Level: Hard

  1. Which of the following would you expect to have the most negative S?

Ans: D

Topic: Entropy

Section 6.2

Difficulty Level: Hard

  1. Of following reactions, which one(s) would you expect to have a negative S?

Ans: A and B

Topic: Gibbs Free Energy

Section 6.3

Difficulty Level: Easy

  1. Predict the sign of G for an exothermic reaction with an increase in entropy.

A. positive

B. negative

C. no change

D. cannot predict without additional information

Ans:B

Topic: Gibbs Free Energy

Section 6.3

Difficulty Level: Easy

  1. Predict the sign of G for an endothermic reaction with an increase in entropy.

A. positive

B. negative

C. no change

D. cannot predict without additional information

Ans:D

Topic: Gibbs Free Energy

Section 6.3

Difficulty Level: Easy

  1. Predict the sign of G for an exothermic reaction with a decrease in entropy.

A. positive

B. negative

C. no change

D. cannot predict without additional information

Ans:D

Topic: Gibbs Free Energy

Section 6.3

Difficulty Level: Easy

  1. Predict the sign of G for an endothermic reaction with a decrease in entropy.

A. positive

B. negative

C. no change

D. cannot predict without additional information

Ans:A

Topic: Equilibria

Section 6.4

Difficulty Level: Easy

  1. Does a reaction with a positive G favor reactants or products?

Ans: Reactants

Topic: Equilibria

Section 6.4

Difficulty Level: Easy

  1. Does a reaction with a negative G favor reactants or products?

Ans: Products

Topic: Equilibria

Section 6.4

Difficulty Level: Hard

  1. Does a reaction with a positive S and a positive H favor reactants or products?

Ans: Cannot determine without additional information

Topic: Equilibria

Section 6.4

Difficulty Level: Hard

  1. Does a reaction with a positive S and a negative H favor reactants or products?

Ans: Products

Topic: Equilibria

Section 6.4

Difficulty Level: Easy

  1. Does a reaction with a Keq = 10 favor reactants or products?

Ans: Products

Topic: Equilibria

Section 6.4

Difficulty Level: Hard

  1. Does a reaction with a H of 14 kJ/mol and a S of 150 J/molK at 298 K favor reactants or products?

Ans: Products

Topic: Equilibria

Section 6.4

Difficulty Level: Hard

  1. Does a reaction with a H of 20 kJ/mol and a S of 10 J/mol K at 298 K favor reactants or products?

Ans: Reactants

Topic: Kinetics

Section 6.5

Difficulty Level: Easy

  1. Given the following rate law, what is the order of the reaction with respect to MeI?

Ans: first

Topic: Kinetics

Section 6.5

Difficulty Level: Easy

  1. Given the following rate law, what is the order of the reaction with respect to tert-butyl iodide?

Ans: first

Topic: Kinetics

Section 6.5

Difficulty Level: Easy

  1. Given the following rate law, what is the order of the reaction with respect to sodium cyanide?

Ans: second

Topic: Kinetics

Section 6.5

Difficulty Level: Easy

  1. What is the energy of activation for the following reaction?

Ans: 10 kJ/mol

Topic: Kinetics

Section 6.5

Difficulty Level: Hard

  1. What is the energy of activation for the following reaction?

Ans: 10 kJ/mol

Topic: Kinetics

Section 6.5

Difficulty Level: Easy

  1. Based on the following energy diagram, is the reaction exothermic or endothermic?

Ans: exothermic

Topic: Kinetics

Section 6.5

Difficulty Level: Easy

  1. Based on the following energy diagram, is the reaction exothermic or endothermic?

Ans: endothermic

Topic: Kinetics

Section 6.5

Difficulty Level: Hard

  1. What is the effect of a catalyst on a reaction?

A. It increases the rate.

B. It decreases the entropy.

C. It changes the equilibrium.

D. It makes the products more stable.

Ans: A

Topic: Kinetics

Section 6.5

Difficulty Level: Easy

  1. Which of the following describes the effect of a catalyst on a reaction?

A. It lowers the free energy of the products.

B. It makes the reactants less stable.

C. It changes the equilibrium constant.

D. It lowers the energy of activation.

Ans: D

Topic: Reading Energy Diagrams

Section 6.6

Difficulty Level: Medium

  1. Which of the following is an energy diagram for a three-step reaction?

Ans: B

Topic: Reading Energy Diagrams

Section 6.6

Difficulty Level: Medium

  1. Which of the following is an energy diagram for a two-step reaction?

Ans: B

Topic: Reading Energy Diagrams

Section 6.6

Difficulty Level: Medium

  1. Draw an energy diagram for an endothermic reaction with two steps.

Ans:

Topic: Reading Energy Diagrams

Section 6.6

Difficulty Level: Medium

  1. Draw an energy diagram for a three-step reaction.

Ans:

Topic: Reading Energy Diagrams

Section 6.6

Difficulty Level: Hard

  1. Draw an energy diagram for a concerted exothermic reaction.

Ans:

Topic: Reading Energy Diagrams

Section 6.6

Difficulty Level: Medium

  1. Which of the following energy diagrams shows a concerted endothermic reaction?

Ans: D

Topic: Reading Energy Diagrams

Section 6.6

Difficulty Level: Medium

  1. Which of the following energy diagrams shows the reaction with the smallest energy of activation?

Ans: A

Topic: Reading Energy Diagrams

Section 6.6

Difficulty Level: Easy

  1. What is a transition state?

A. An isolable intermediate in a reaction.

B. The starting materials of the reaction.

C. A local maximum on the energy diagram.

D. A low-energy point between the starting materials and the product.

Ans: C

Topic: Reading Energy Diagrams

Section 6.6

Difficulty Level: Easy

  1. What is an intermediate?

A. A local maximum on the energy diagram.

B. A point on the reaction pathway that has a discrete lifetime.

C. A point half-way between the starting materials and products.

D. The highest energy compound on an energy diagram.

Ans: B

Topic: Reading Energy Diagrams

Section 6.6

Difficulty Level: Easy

  1. Which of the following energy diagrams is of a reaction with one transition state?

Ans: A

Topic: Reading Energy Diagrams

Section 6.6

Difficulty Level: Easy

  1. Which of the following energy diagrams is of a reaction with one intermediate?

Ans: B

Topic: Nucleophiles and Electrophiles

Section 6.7

Difficulty Level: Easy

  1. Identify the nucleophilic site in the following molecule.

Ans:

Topic: Nucleophiles and Electrophiles

Section 6.7

Difficulty Level: Easy

  1. Identify the nucleophilic site in the following molecule.

Ans:

Topic: Nucleophiles and Electrophiles

Section 6.7

Difficulty Level: Hard

  1. Identify the nucleophilic site(s) in the following molecule.

Ans:

Topic: Nucleophiles and Electrophiles

Section 6.7

Difficulty Level: Medium

  1. Identify the nucleophilic centers in the following molecule.

Ans:

Topic: Nucleophiles and Electrophiles

Section 6.7

Difficulty Level: Easy

  1. Identify the nucleophilic atom in the following molecule.

A. P

B. C

C. H

D. Me

Ans: A

Topic: Nucleophiles and Electrophiles

Section 6.7

Difficulty Level: Hard

  1. Identify the electrophilic site in the following molecule.

Ans:

Topic: Nucleophiles and Electrophiles

Section 6.7

Difficulty Level: Easy

  1. Identify the electrophilic site in the following molecule.

A. H

B. C of carbonyl

C. Cother than carbonyl

D. O of carbonyl

Ans: B

Topic: Nucleophiles and Electrophiles

Section 6.7

Difficulty Level: Medium

  1. Identify the electrophilic site in the following molecule.

Ans:

Topic: Nucleophiles and Electrophiles

Section 6.7

Difficulty Level: Easy

  1. Identify the electrophilic site in the following molecule.

Ans:

Topic: Nucleophiles and Electrophiles

Section 6.7

Difficulty Level: Hard

  1. Identify the electrophilic site in the following molecule.

A. C

B. O

C. B

D. No electrophilic site

Ans: C

Topic: Nucleophiles and Electrophiles

Section 6.7

Difficulty Level: Easy

  1. Which of the following cannot be a nucleophile?

Ans; A

Topic: Nucleophiles and Electrophiles

Section 6.7

Difficulty Level: Easy

  1. Which of the following cannot be an electrophile?

Ans: D

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Easy

  1. Which of the following is hydride?

A. H+

B. H

C. H−

D. H2

Ans: C

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Medium

  1. Draw the structure of hydride.

Ans:

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Easy

  1. Which of the following is the most stable cation?

Ans: C

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Easy

  1. For the following reaction step, indicate which pattern of arrow pushing it represents.

A. Proton transfer

B. Loss of leaving group

C. Nucleophilic attack

D. Rearrangement

Ans: A

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Easy

  1. For the following reaction step, indicate which pattern of arrow pushing it represents.

A. Proton transfer

B. Loss of leaving group

C. Nucleophilic attack

D. Rearrangement

Ans: C

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Medium

  1. For the following reaction step, indicate which pattern of arrow pushing it represents.

Ans: Nucleophilic attack

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Easy

  1. For the following reaction step, indicate which pattern of arrow pushing it represents.

A. Proton transfer

B. Loss of leaving group

C. Nucleophilic attack

D. Rearrangement

Ans: B

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Easy

  1. For the following reaction step, indicate which pattern of arrow pushing it represents.

A. Proton transfer

B. Loss of leaving group

C. Nucleophilic attack

D. Rearrangement

Ans: A

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Easy

  1. For the following reaction step, indicate which pattern of arrow pushing it represents.

A. Proton transfer

B. Loss of leaving group

C. Nucleophilic attack

D. Rearrangement

Ans: D

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Easy

  1. For the following reaction step, indicate which pattern of arrow pushing it represents.

A. Proton transfer

B. Loss of leaving group

C. Nucleophilic attack

D. Rearrangement

Ans: C

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Medium

  1. Melphalan, a drug used in chemotherapy, reacts with itself in the body before binding with its target, as illustrated in the mechanism below. Which two patterns of arrow pushing are seen in this reaction?

Ans. Nucleophilic attack and loss of leaving group

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Medium

  1. Melphalan, a drug used in chemotherapy, reacts with itself before binding with its target in the body, as illustrated below. Draw in the curved arrows that account for this transformation.

Ans.

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Medium

  1. The following reaction has three mechanistic steps. Draw all curved arrows necessary to complete the mechanism.

Ans.

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Easy

  1. What is wrong with the following mechanism?

A. There is no leaving group, so there should be no arrows.

B. The arrow should be removing a proton from the H2O group.

C. An arrow is also needed to indicate the loss of the leaving group.

D. The arrow is backwards.

Ans: C

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Hard

  1. What is wrong with the following mechanism?

A. There is no leaving group, so there should be no arrows.

B. The arrow should be removing a proton from the H2O group.

C. An arrow is also needed to indicate the loss of the leaving group.

D. The arrow indicating the formation of the C-Br bond (nucleophilic attack) should start at the bromide anion.

Ans: D

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Easy

  1. Which of the following mechanistic steps representsa nucleophilic attack?

Ans: B

Topic: Mechanisms and Arrow Pushing

Section 6.8

Difficulty Level: Easy

  1. Which of the following mechanistic steps representsthe loss of a leaving group?

Ans: C

Topic: Combining Patterns

Section 6.9

Difficulty Level: Easy

  1. Identify the sequence of curved arrows (electron movement) in the steps of the following reaction.

A. Proton transfer, proton transfer

B. Proton transfer, loss of leaving group

C. Nucleophilic attack, proton transfer

D. Proton transfer, nucleophilic attack

Ans: A

Topic: Combining Patterns

Section 6.9

Difficulty Level: Medium

  1. The following reaction has three mechanistic steps. Identify the pattern of arrow pushing steps in each step.

Ans. Proton transfer; loss of leaving group, nucleophilic attack

Topic: Combining Patterns

Section 6.9

Difficulty Level: Hard

  1. Identify the sequence of curved arrows (electron movement) in the steps of the following reaction.

A. Proton transfer, proton transfer, nucleophilic Attack

B. Proton transfer, loss of leaving group

C. Nucleophilic attack, proton transfer, loss of leaving group

D. Proton transfer, nucleophilic attack, proton transfer

Ans: D

Topic: Combining Patterns

Section 6.9

Difficulty Level: Hard

  1. Identify the sequence of curved arrows (electron movement) in the steps of the following reaction.

A. Proton transfer, proton transfer, nucleophilic attack

B. Proton transfer, loss of leaving group, nucleophilic attack, proton transfer

C. Nucleophilic attack, proton transfer, loss of leaving group

D. Proton transfer, loss of leaving group, proton transfer, nucleophilic attack

Ans: B

Topic: Combining Patterns

Section 6.9

Difficulty Level: Easy

  1. Identify the sequence of curved arrows (electron movement) in the steps of the following reaction.

A. Proton transfer, proton transfer

B. Proton transfer, loss of leaving group

C. Nucleophilic attack, proton transfer

D. Proton transfer, nucleophilic attack

Ans: D

Topic: Combining Patterns

Section 6.9

Difficulty Level: Hard

  1. What pattern of curved arrow pushingis the second step of this reaction?

A. Proton transfer

B. Loss of leaving group

C. Nucleophilic attack

D. Rearrangement

Ans: B

Topic: Combining Patterns

Section 6.9

Difficulty Level: Easy

  1. What pattern of curved arrow pushing is the fourth step of this reaction?

A. Proton transfer

B. Loss of leaving group

C. Nucleophilic attack

D. Rearrangement

Ans: A

Topic: Combining Patterns

Section 6.9

Difficulty Level: Easy

  1. What pattern of curved arrow pushing is the second step of this reaction?

A. Proton transfer

B. Loss of leaving group

C. Nucleophilic attack

D. Rearrangement

Ans: C

Topic: Combining Patterns

Section 6.9

Difficulty Level: Easy

  1. What pattern of curved arrow pushing is the second step of this reaction?

A. Proton transfer

B. Loss of leaving group

C. Nucleophilic attack

D. Rearrangement

Ans: B

Topic: Combining Patterns

Section 6.9

Difficulty Level: Hard

  1. What pattern of curved arrow pushing is the second step of this reaction?

Ans: Nucleophilic attack

Topic: Drawing Curved Arrows

Section 6.10

Difficulty Level: Hard

  1. Draw arrows for each step of the following reaction.

Ans:

Topic: Drawing Curved Arrows

Section 6.10

Difficulty Level: Hard

  1. Draw curved arrows for each step of the following reaction.

Ans:

Topic: Drawing Curved Arrows

Section 6.10

Difficulty Level: Hard

  1. Draw curved arrows for the following mechanistic step.

Ans:

Topic: Drawing Curved Arrows

Section 6.10

Difficulty Level: Medium

  1. Identify the nucleophilic and electrophilic sites in the reactants of the following reaction.