Question 1

Which of the following statements best describes the difference between thermodynamics and kinetics in the study of chemical reactions?

Accepted Answer

Thermodynamics is concerned with the energy changes and equilibrium position, while kinetics is concerned with the reaction rate.

Question 2

In the free-radical chlorination of methane, what is the role of blue light?

Accepted Answer

It initiates the reaction by homolytically cleaving the Cl-Cl bond.

Question 3

Which of the following is the correct expression for the equilibrium constant $$K_{eq}$$ for the reaction $$aA + bB \rightleftharpoons cC + dD$$?

Accepted Answer

$$K_{eq} = \frac{[C]^c[D]^d}{[A]^a[B]^b}$$

Question 4

A reaction has $$\Delta G^\circ = -108.7 kJ/$$mol at 25°C. What does this indicate about the reaction?

Accepted Answer

The reaction is spontaneous and strongly favors product formation.

Question 5

Which of the following best describes the propagation step in the free-radical chain reaction of methane chlorination?

Accepted Answer

A chlorine atom abstracts a hydrogen from methane, forming HCl and a methyl radical.

Question 6

Given the rate law $$	ext{rate} = k[A]^2[B]$$, what is the overall order of the reaction?

Accepted Answer

Third order

Question 7

Which of the following statements about activation energy ($$E_a) is $$correct?

Accepted Answer

$$E_a is $$the minimum kinetic energy required for reactants to form products.

Question 8

Which of the following is true regarding the stability of free radicals?

Accepted Answer

Tertiary radicals are more stable than secondary radicals.

Question 9

What is the effect of increasing temperature on the rate of a reaction, according to the Arrhenius equation?

Accepted Answer

The rate increases because more molecules have energy greater than $$E_a.$$

Question 10

Which of the following best explains why radical inhibitors are added to food products?

Accepted Answer

They combine with free radicals to form stable molecules, slowing spoilage.

Question 11

Which of the following is the correct formula for the free energy change ($$\Delta G^\circ) in $$terms of the equilibrium constant ($$K_{eq}$$)?

Accepted Answer

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

Question 12

Which of the following statements about the Hammond Postulate is correct?

Accepted Answer

In an endothermic reaction, the transition state resembles the product.

Question 13

Which of the following is a termination step in the free-radical chlorination of methane?

Accepted Answer

Two chlorine radicals combine to form $$Cl_2.$$

Question 14

Which of the following best describes the effect of bond dissociation energy (BDE) on reaction enthalpy?

Accepted Answer

Bond dissociation requires energy (+BDE), and bond formation releases energy (-BDE).

Question 15

Which of the following is the correct order of stability for carbocations?

Accepted Answer

Tertiary \u003e secondary \u003e primary \u003e methyl

Question 16

Which of the following statements about carbanions is correct?

Accepted Answer

Carbanions are nucleophilic and basic.

Question 17

Which of the following best describes a carbene?

Accepted Answer

A neutral carbon species with a lone pair and an empty p orbital.

Question 18

In the bromination of propane, why is the secondary bromide the major product?

Accepted Answer

Secondary hydrogens are much more reactive toward bromine radicals than primary hydrogens.

Question 19

Which of the following is true about the entropy change ($$\Delta S^\circ) in a $$chemical reaction?

Accepted Answer

Increasing the number of particles increases entropy.

Chapter 4: The Study of Chemical Reactions – Thermodynamics, Kinetics, and Mechanisms in Organic Chemistry

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