Chapter 20.3, Problem 20.6BFP

(a)

Interpretation Introduction

Interpretation:

The signs of the entropy ${\text{ΔS}}^{\text{o}}$ and enthalpy ${\text{ΔH}}^{\text{o}}$ change expected for given reaction process have to be identified.

Concept introduction:

Entropy change:

The sign of ${\text{ΔS}}^{\text{o}}$ for a reaction is determined by using the following rules:

• When a molecule is broken down and gives two or more smaller molecules.
• When the moles of gas is increases (by the breaking of molecules)
• Solid changes to liquid or gas state or liquid state changes to gas state.

Entropy$\left(S\right)$: it is used to describe the disorder. It is the amount of arrangements possible in a system at a particular state.

If the disorder increases in a system, then $\Delta S>0$ positive

If the disorder decreases in a system, then $\Delta S<0$ negative

If the disorder equal in a system, then $\Delta S=0$

(b)

Interpretation Introduction

Interpretation:

The temperature at which $\text{ΔG}$ is less than 0 have to be explained.

Concept introduction:

Enthalpy change of reaction:

The enthalpy change of a reaction is given by

  $\begin{array}{l}\text{ΔH}\text{=}{\displaystyle \sum {\text{nΔH}}_{\text{f}}{}^{\text{o}}\left(\text{products}\right)}\text{-}{\displaystyle \sum {\text{mΔH}}_{\text{f}}{}^{\text{o}}\left(\text{products}\right)}\\ \text{where,}\\ \text{ΔH}\text{-}\text{enthalpy}\text{change}\\ {\text{ΔH}}_{\text{f}}{}^{\text{o}}\text{-}\text{enthalpy}\text{change}\text{of}\text{formation}\end{array}$

Free energy:

Free energy is measured by subtracting the product of temperature and entropy from the enthalpy of a system.

  $\begin{array}{l}\text{G}\text{=}\text{H}\text{-}\text{TS}\\ \text{where,}\\ \text{G}\text{-}\text{free}\text{energy;}\text{H}\text{-}\text{enthalpy}\\ \text{S}\text{-}\text{entropy and T}\text{-temperature}\text{.}\end{array}$

Relationship between ${\text{ΔG}}^{\text{o}}\text{,}{\text{ΔH}}^{\text{o}}\text{and}{\text{ΔS}}^{\text{o}}$ is given by

  $\begin{array}{l}{\text{ΔG}}^{\text{o}}\text{=}{\text{ΔH}}^{\text{o}}\text{-}{\text{TΔS}}^{\text{o}}\\ \text{where,}\\ {\text{ΔG}}^{\text{o}}\text{-}\text{standard}\text{free}\text{energy}\text{change;}{\text{ΔH}}^{\text{o}}\text{-}\text{standard}\text{enthalpy}\text{change}\\ {\text{ΔS}}^{\text{o}}\text{-}\text{standard}\text{entropy}\text{change and T}\text{-}\text{temperature}\end{array}$