Chapter 3, Problem 12PP

Interpretation Introduction

Interpretation:

The Gibbs free energy and required change in enthalpy for a reaction system are to be calculated with given ${\text{K}}_{eq}$ value.

Concept introduction:

Gibbs Free Energy can be defined as

$\text{ΔG° = ΔH° - TΔS°}$ …… (1)

Here, $\text{ΔG°}$ is the Gibbs free energy, $\text{ΔH°}$ is the enthalpy change, and $\text{ΔS°}$ is the entropy change at constant temperature T and constant pressure.

When the change in entropy is negligible or zero, the equation changes to the expression: $\begin{array}{l}\text{ΔH° = ΔG° + }{\cancel{\text{TΔS°}}}^{\text{Goes to Zero}}\\ \text{ΔH° = ΔG°}\end{array}$

Second law of thermodynamics tells about the spontaneity of a reaction and Gibbs free energy will tell in which direction the reaction is spontaneous.

It can be expressed mathematically as

$\text{ΔG°}=-\text{RT}\ln K_{eq}$ ……. (2)

Here, $\text{ΔG°}$ is the Gibbs free energy, R is the universal gas constant, T is the temperature, and ${\text{K}}_{eq}$ is the equilibrium constant.