Chapter 16, Problem 71QAP

Interpretation Introduction

Interpretation:

The standard Gibbs free energy ${\text{ΔG}}^{\text{0}}$ for the following overall reaction needs to be deduced from the given contributing reactions.

${\text{SO}}_{\text{2}}{\text{(g) + CO(g) + 2H}}_{\text{2}}\text{(g)}\to {\text{COS(g) + 2H}}_{\text{2}}\text{O(g)}$

Concept introduction:

1. The change in the Gibbs free energy, ΔG is a thermodynamic function which governs the spontaneity of a chemical reaction. The negative value of ΔG represents that the reaction is spontaneous, whereas, the positive value represents that the reaction is non-spontaneous, and if ΔG = 0, then it represents that the reaction is at equilibrium.
2. The standard Gibbs free energy, ${\text{ΔG}}^{\text{0}}$ is the value measured under standard conditions i.e. Pressure = 1 atm and Temperature = 25° C.
3. 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

4. Free energy changes for reactions are additive. If a net reaction is a composite of two reactions with free energy represented as, ΔG₁ and ΔG₂ respectively, then the free energy change for the net reaction would be:

${\text{ΔG = ΔG}}_{\text{1}}{\text{ + ΔG}}_{\text{2}}\text{ ------(2)}$