Q: In the context of bond dissociation enthalpy (BDE), which formula is used to estimate the enthalpy change of a reaction?

$$\Delta H = \text{Bonds broken} - \text{Bonds formed}$$

Question 1

Which step in a radical chain reaction is responsible for creating two radicals from non-radical species?

Accepted Answer

Initiation

Question 2

Given the reaction $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$, which statement best describes why this reaction proceeds to completion?

Accepted Answer

The equilibrium constant $$K is $$much greater than 1.

Question 3

Which equation correctly relates the Gibbs free energy change to the equilibrium constant?

Accepted Answer

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

Question 4

A reaction is considered thermodynamically favorable if:

Accepted Answer

$$\Delta G is $$negative

Question 5

Which of the following best describes the role of entropy ($$\Delta S) in $$chemical reactions?

Accepted Answer

It quantifies the randomness or disorder of a system.

Question 6

In the context of bond dissociation enthalpy (BDE), which formula is used to estimate the enthalpy change of a reaction?

Accepted Answer

$$\Delta H = 	ext{Bonds broken} - 	ext{Bonds formed}$$

Question 7

Which of the following is an example of increasing entropy in a chemical system?

Accepted Answer

Cracking of a large hydrocarbon into smaller fragments

Question 8

A reaction has $$\Delta H = -25$$ kcal/mol. What does this indicate about the reaction?

Accepted Answer

The reaction is exothermic.

Question 9

Which statement about heterolytic cleavage is correct?

Accepted Answer

It forms ions and is highly dependent on solvation.

Question 10

For the reaction $$\mathrm{CH_3Br + NaOH ightarrow CH_3OH + NaBr}$$, the rate law is $$	ext{Rate} = k[\mathrm{CH_3Br}][\mathrm{NaOH}]. $$What is the overall order of the reaction?

Accepted Answer

Second order

Question 11

Which factor does NOT directly affect the rate constant ($$k) in $$the Arrhenius equation?

Accepted Answer

Concentration of reactants

Question 12

According to the Arrhenius equation $$k = Ae$$^{-E_a/RT}$$, what happens to the rate constant k$ as temperature increases?

Accepted Answer

It increases exponentially.

Question 13

Which of the following best describes an intermediate in a reaction coordinate diagram?

Accepted Answer

A local minimum with a finite lifetime

Question 14

In a reaction where $$\Delta S \u003e 0$$ and $$\Delta H \u003c 0$$, what can be said about the spontaneity at room temperature?

Accepted Answer

The reaction is always spontaneous.

Question 15

Which of the following is a plausible reason why increasing the concentration of reactants increases the rate of a chemical reaction?

Accepted Answer

It increases the frequency of molecular collisions.

Question 16

A reaction is described as 'exergonic.' What does this mean in terms of Gibbs free energy?

Accepted Answer

$$\Delta G \u003c 0$$

Question 17

Which of the following best explains why catalysts increase the rate of a reaction?

Accepted Answer

They lower the activation energy ($$E_a).$$

Question 18

In a multi-step reaction, which step determines the overall rate?

Accepted Answer

The slowest step (rate-determining step)

Question 19

Which of the following statements about equilibrium is correct?

Accepted Answer

At equilibrium, the rates of the forward and reverse reactions are equal.

Question 20

Which of the following is a correct interpretation of the equation $$\Delta G = \Delta H - T\Delta S$$?

Accepted Answer

Gibbs free energy is determined by both enthalpy and entropy changes.

Chapter 4 Thermodynamics and Kinetics in Organic Chemistry: Radical Reactions, Equilibrium, and Reaction Rates

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