Chapter 20, Problem 20.94P

(a)

Interpretation Introduction

Interpretation:

The given reaction equation should be balanced.

Concept introduction:

In a balanced equation the number of atoms of each element as a reactant is equal to the number of atoms of that element as a product.

Coefficient is a number placed before a formula in a chemical equation.

A balanced equation should be obeying the law of conservation of mass. “Law of conservation of mass” states that, the number of atoms remains constant throughout the reaction, simply it can be stated as follows, “during a chemical reaction atoms are neither be created nor be destroyed”.

(b)

Interpretation Introduction

Interpretation:

For the gaseous reaction the ${\text{ΔG}}^{\text{o}}$ value has to be determined.

Concept introduction:

Free energy (Gibbs free energy) is the term that is used to explain the total energy content in a thermodynamic system that can be converted into work.  The free energy is represented by the letter $\text{G}$.  All spontaneous process is associated with the decrease of free energy in the system.  The standard free energy change ${\text{(ΔG}}^{\text{°}}{}_{\text{rxn}})$ is the difference in free energy of the reactants and products in their standard state.

${\text{ΔG}}^{\text{°}}{}_{\text{rxn}}\text{=}\sum {\text{nΔG}}_{\text{f}}{}^{\text{°}}\text{(Products)-}\sum {\text{nΔG}}_{\text{f}}{}^{\text{°}}\text{(Reactants)}$

(c)

Interpretation Introduction

Interpretation:

For the given reaction, the ${\text{ΔG}}_{\text{rxn}}$ value should be found at $298K$ using given pressure values.

Concept introduction:

Reaction quotient$\left(Q\right)$: Reaction quotient and equilibrium constant has same expression.  Reaction quotient is also the ratio between the concentrations of the reactant to product, but these concentrations are not necessarily the equilibrium concentrations.

        $Q=\frac{\left[\text{Product}\right]}{\left[\text{Reactant}\right]}$

The reaction quotient $\left(Q\right)$ is helpful in predicting the direction of the reaction.

• When $\text{Q}\text{>}{\text{K}}_{\text{c}}$, the reaction proceeds towards left to increase the concentration of the reactants.
• When $\text{Q}<{\text{K}}_{\text{c}}$, the reaction proceeds towards right to increase the concentration of the products.
• When $\text{Q}={\text{K}}_{\text{c}}$, the reaction is at equilibrium.

Free energy change$\text{ΔG}$: change in the free energy takes place while reactants convert to product where both are in standard state. It depends on the equilibrium constant $\text{K}$

  $\begin{array}{l}\text{ΔG =}{\text{ΔG}}^{\text{o}}\text{+}\text{RT}\ln \left(\text{K}\right)\\ {\text{ΔG}}^{\text{o}}\text{=}{\text{ΔH}}^{\text{o}}-{\text{TΔS}}^{\text{o}}\end{array}$

  Where,

  $\text{T}$ is the temperature

  $\text{ΔG}$ is the free energy

  ${\text{ΔG}}^{\text{o}}$, ${\text{ΔH}}^{\text{o}}$ and ${\text{ΔS}}^{\text{o}}$ is standard free energy, enthalpy and entropy values.