Chapter 6, Problem 50P

Interpretation Introduction

(a)

Interpretation: The validation of the given statement, “Increasing temperature increases reaction rate” is to be stated.

Concept introduction: According to Le Chatelier’s principle, equilibrium of the reaction shift towards the side that involves absorption of heat when the temperature is increased. The kinetic energy of molecules increases on increasing the temperature. It results in the faster rate of the reaction.

Interpretation Introduction

(b)

Interpretation: The validation of the given statement, “If a reaction is fast, it has a large rate constant” is to be stated.

Concept introduction: The rate constant is represented by $k$. It affects the rate of a reaction. Both the rate of a reaction and rate constant are directly related.

Interpretation Introduction

(c)

Interpretation: The validation of the given statement, “A fast reaction has a large negative $\text{Δ}G°$ value” is to be stated.

Concept introduction: The change in Gibbs free energy, enthalpy and entropy is represented by $\text{Δ}G°$, $\text{Δ}H\text{°}$ and $\text{Δ}S\text{°}$ respectively. They are state functions. The relation of $\text{Δ}G°$ with $\text{Δ}H\text{°}$ and $\text{Δ}S\text{°}$ is shown as,

$\text{Δ}G\text{°}=\text{Δ}H\text{°}-T\text{Δ}S\text{°}$

The change in Gibbs free energy describes the spontaneity of the reaction. The change in enthalpy describes the relative bond strength in the substance, whereas the change in entropy describes the randomness in the system.

Interpretation Introduction

(d)

Interpretation: The validation of the given statement, “When $E_{\text{a}}$ is large, the rate constant $\text{k}$ is also large” is to be stated.

Concept introduction: The activation energy $\left(E_{\text{a}}\right)$ aids in determining the rate of the chemical reactions. The small value of $E_{\text{a}}$ implies that less energy is required to convert the reactants into products, which further increases the rate of reaction.

Interpretation Introduction

(e)

Interpretation: The validation of the given statement, “Fast reactions have equilibrium constants $>1$” is to be stated.

Concept introduction: The change in Gibbs free energy is represented by $\text{Δ}G°$. It is a state function. The value of $\text{Δ}G°$ depends on $K_{\text{eq}}$. The free energy change is calculated as,

$\text{Δ}G\text{°}=-2.303\text{R}T\log K_{\text{eq}}$

If the $\text{Δ}G°$ is greater than zero and $K_{\text{eq}}$ is smaller than one, then the formation of starting material is favored at equilibrium. However, if the $\text{Δ}G°$ is smaller than zero and $K_{\text{eq}}$ is greater than one, the formation of product is favored at equilibrium. The equilibrium constant does not influence the rate of reaction.

Interpretation Introduction

(f)

Interpretation: The validation of the given statement, “Increasing the concentration of a reactant always increases the rate of a reaction” is to be stated.

Concept introduction: The concentration of a reaction influences the rate of a reaction. The increase in concentration of a starting material results in increase of the rate of a reaction.