Question 1

Which of the following statements best describes the role of an electrophile in an organic reaction, as illustrated in the first image?

Accepted Answer

An electrophile accepts an electron pair, and if it is positively charged, it becomes neutral after the reaction.

Question 2

According to the octet rule, as shown in the third image, what must happen if an electron pair moves to a second-row atom that already has an octet?

Accepted Answer

Another electron pair must simultaneously leave that atom to maintain the octet.

Question 3

Which of the following best describes a radical, as discussed in the lecture and shown in the fourth and fifth images?

Accepted Answer

A radical is a highly reactive species with an atom that has an odd number of electrons in its valence shell.

Question 4

In the industrial chlorination of methane, which type of reaction mechanism is primarily involved?

Accepted Answer

Radical chain reaction

Question 5

Given the equilibrium constant $$K_{eq} = 7.1 	imes 10^7$ for the reaction $$\mathrm{H_2C=$$CH_2 + $$HBr ightleftharpoons CH_3CH_2Br}$$, what does this value indicate about the reaction at equilibrium?

Accepted Answer

The reaction strongly favors the formation of $$\mathrm{CH_3CH_2Br}.$$

Question 6

Which equation correctly relates the standard Gibbs free energy change ($$\Delta G^\circ) to $$the equilibrium constant ($$K_{eq}$$)?

Accepted Answer

$$\Delta G^\circ = -RT \ln K_{eq}$$

Question 7

A reaction has $$\Delta G^\circ \u003c 0. $$What can you conclude about $$K_{eq}$$ and the direction of the reaction?

Accepted Answer

$$K_{eq} \u003e 1$$; the reaction favors products.

Question 8

Which of the following best describes bond dissociation energy (D)?

Accepted Answer

The energy required to break a specific bond in a molecule to produce two radical fragments in the gas phase at 25°C.

Question 9

The C–H bond in methane has a bond dissociation energy of $$439.3\ \mathrm{kJ/mol}. $$What does this imply about the bond?

Accepted Answer

It is a relatively strong bond and requires significant energy to break.

Question 10

In the radical reaction mechanism for the industrial production of chloromethane, which step involves the formation of a methyl radical ($$\cdot \mathrm{CH_3$}$$)?

Accepted Answer

Propagation step: $$\cdot \mathrm{Cl}$$ abstracts a hydrogen atom from $$\mathrm{CH_4$}$$, forming $$\cdot \mathrm{CH_3$}$$ and $$\mathrm{HCl}.$$

Question 11

Which of the following is true regarding the relationship between $$\Delta G^\circ$$, $$K_{eq}$$, and the direction of energy flow in a chemical reaction?

Accepted Answer

If $$K_{eq} \u003e 1$$, $$\Delta G^\circ is $$negative and energy is released.

Question 12

Which of the following best explains why radical reactions are highly reactive and important in biological and industrial processes?

Accepted Answer

Radicals contain an atom with an unpaired electron, making them highly reactive and able to initiate chain reactions.

Question 13

In the context of the ATP hydrolysis reaction shown in the last image, why is the hydrolysis of ATP to ADP considered energetically favorable?

Accepted Answer

The bond being broken in ATP is weaker than the bonds formed in ADP and $$\mathrm{H_2O}$$, resulting in a large negative $$\Delta H^\circ.$$

Question 14

Which of the following scenarios would violate the octet rule for second-row elements, as described in the lecture?

Accepted Answer

A carbon atom with five bonds and no formal charge.

Question 15

A reaction has $$\Delta G^\circ = +10\ \mathrm{kJ/mol}. $$What can you infer about the equilibrium constant $$K_{eq}$$ and the favorability of the reaction?

Accepted Answer

$$K_{eq} \u003c 1$$; the reaction is reactant-favored.

Question 16

Which of the following best describes the propagation step in a radical chain reaction, such as the chlorination of methane?

Accepted Answer

A radical reacts with a stable molecule to form a new radical and a new molecule, continuing the chain.

Question 17

Which of the following is a correct statement about the relationship between bond dissociation energy and bond strength?

Accepted Answer

A higher bond dissociation energy indicates a stronger bond.

Question 18

In the radical addition reaction of an alkene, as shown in the fifth image, what is the result of the addition of a radical to the double bond?

Accepted Answer

A new radical is formed at one of the carbons of the former double bond.

Chapter 6: An Overview of Organic Reactions – Mechanisms, Radicals, and Energetics

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