Chapter 14.5, Problem 6PPC

Interpretation Introduction

Interpretation:

The substances having zero value for the free energy of formation ${\text{(ΔG}}_{\text{f}}{}^{\text{°}}\text{= 0)}$ has to be found from the given set of substances.

Concept introduction:

Free energy is the term that is used to explain the total energy content in a thermodynamic system that can be converted into work.  The free energy is represented by the letter G.  All spontaneous process is associated with the decrease of free energy in the system.  The equation given below helps us to calculate the change in free energy in a system.

$\text{ΔG = }\Delta {\rm H}\text{- T}\Delta \text{S}$

Where,

$\text{ΔG }$ is the change in free energy of the system

$\Delta {\rm H}$ is the change in enthalpy of the system

$\text{T}$ is the absolute value of the temperature

$\Delta \text{S}$ is the change in entropy in the system

Standard free energy of formation is the change in free energy for the formation of one mole of substance in its standard state.  The standard state is $\text{1}\text{atm}$ pressure and 298K temperature.  The formation of most stable form of any substances will have zero value for the free energy of formation ${\text{(ΔG}}_{\text{f}}{}^{\text{°}}\text{= 0)}$.  For example the free energy change for the formation of oxygen molecule is zero ${\text{(ΔG}}_{\text{f}}{}^{\text{°}}{\text{(O}}_2\text{(g))}\text{= 0)}$.