Chapter 20, Problem 20.7P

(a)

Interpretation Introduction

Interpretation:

The entropy of a perfect crystal has to be determined at $0K$.

Concept introduction:

Entropy is a thermodynamic quantity, which is the measure of randomness in a system.  The term entropy is useful in explaining the spontaneity of a process.  For all spontaneous process in an isolated system there will be an increase in entropy.  Entropy is represented by the letter ‘S’.  It is a state function.  The change in entropy gives information about the magnitude and direction of a process.  Factors like temperature, molar mass, molecular complexity and phase transition occurring in a reaction influences the entropy in a system.

  ${\text{ΔS}}_{\text{denatuaration}}\text{=}\frac{{\text{ΔΗ}}_{\text{denaturation}}}{{\text{T}}_{\text{melting}}}$

(b)

Interpretation Introduction

Interpretation:

For the given process, the response of entropy as the temperature rises has to be determined.

Concept introduction:

Any natural process or a chemical reaction taking place in a laboratory can be classified into two categories, spontaneous or nonspontaneous. Spontaneous process occurs by itself, without the influence of external energy. In spontaneous process the free energy of the system decreases and entropy of the system increases.  Nonspontaneous process requires an external influence for initiation.  In nonspontaneous process the free energy of the system increases but entropy of the system decreases.

(c)

Interpretation Introduction

Interpretation:

The reason that why $\Delta H_f^o=0$ and ${\text{S}}^{\text{o}}\text{>0}$ has to be explained.

Concept introduction:

Third law of thermodynamics states that the entropy of a pure crystalline substance at absolute zero at $0K$ .

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 $\Delta S=0$

(d)

Interpretation Introduction

Interpretation:

The reason that why appendix list contains ${\text{ΔH}}_{\text{f}}^{\text{o}}$ values but not ${\text{ΔS}}_{\text{f}}^{\text{o}}$ values has to be stated.

Concept introduction:

Third law of thermodynamics states that the entropy of a pure crystalline substance at absolute zero at $0K$ .

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 $\Delta S=0$