Chapter 16, Problem 95QAP

Interpretation Introduction

(a)

Interpretation:

The standard enthalpy change (ΔH°) for the following reaction should be determined:

${\text{H}}_{\text{2}}\text{O(s)}\to {\text{H}}_{\text{2}}\text{O(l)}$

Concept introduction:

The standard enthalpy of fusion refers to the amount of heat required to melt 1 mole of a solid at its melting point. In the case of ice, the melting point is 0°C.

Interpretation Introduction

(b)

Interpretation:

The standard free change (ΔG°) for the following reaction should be determined

${\text{H}}_{\text{2}}\text{O(s)}\to {\text{H}}_{\text{2}}\text{O(l)}$

Concept introduction:

The change in the Gibbs free energy, ΔG is a thermodynamic function which governs the spontaneity of a chemical reaction. It is the amount of energy required to perform useful work The standard Gibbs free energy ${\text{ΔG}}^{\text{0}}$ for a given chemical reaction can be expressed as a function of temperature, T via the Gibbs-Helmholtz equation.

${\text{ΔG}}^{\text{0}}{\text{ = ΔH}}^{\text{0}}{\text{ - TΔS}}^{\text{0}}\text{ -------(1)}$

where, ${\text{ΔH}}^{\text{0}}$ is the standard enthalpy change, and ${\text{ΔS}}^{\text{0}}$ is the standard entropy change

Interpretation Introduction

(c)

Interpretation:

The standard free change (?S°) for the following reaction should be determined:

${\text{H}}_{\text{2}}\text{O(s)}\to {\text{H}}_{\text{2}}\text{O(l)}$

Concept introduction:

Entropy (S) is a thermodynamic function which measures the disorder or the degree of randomness of a system.

A fusion reaction which involves melting of solid is accompanied by an increase in entropy. The standard molar entropy is expressed as

${\text{ΔS}}^{\text{0}}\text{ = }\frac{{\text{ΔH}}^{\text{0}}}{\text{T}}\text{ -----(2)}$

Interpretation Introduction

(d)

Interpretation:

The standard free change (ΔG°) for the following reaction at T = -20 o C should be determined:

${\text{H}}_{\text{2}}\text{O(s)}\to {\text{H}}_{\text{2}}\text{O(l)}$

Concept introduction:

The change in the Gibbs free energy, ΔG is a thermodynamic function which governs the spontaneity of a chemical reaction. It is the amount of energy required to perform useful work The standard Gibbs free energy ${\text{ΔG}}^{\text{0}}$ for a given chemical reaction can be expressed as a function of temperature, T via the Gibbs-Helmholtz equation.

${\text{ΔG}}^{\text{0}}{\text{ = ΔH}}^{\text{0}}{\text{ - TΔS}}^{\text{0}}\text{ -------(1)}$

where, ${\text{ΔH}}^{\text{0}}$ is the standard enthalpy change, and ${\text{ΔS}}^{\text{0}}$ is the standard entropy change

Interpretation Introduction

(e)

Interpretation:

The standard free change (ΔG°) for the following reaction at T = 20° C should be determined:

${\text{H}}_{\text{2}}\text{O(s)}\to {\text{H}}_{\text{2}}\text{O(l)}$

Concept introduction:

The change in the Gibbs free energy, ΔG is a thermodynamic function which governs the spontaneity of a chemical reaction. It is the amount of energy required to perform useful work The standard Gibbs free energy ${\text{ΔG}}^{\text{0}}$ for a given chemical reaction can be expressed as a function of temperature, T via the Gibbs-Helmholtz equation:

${\text{ΔG}}^{\text{0}}{\text{ = ΔH}}^{\text{0}}{\text{ - TΔS}}^{\text{0}}\text{ -------(1)}$

where, ${\text{ΔH}}^{\text{0}}$ is the standard enthalpy change, and ${\text{ΔS}}^{\text{0}}$ is the standard entropy change