Chapter 2, Problem 2.25P

Interpretation Introduction

Interpretation:

The difference between the standard enthalpy of formation of $C{O}_2$ as currently defined at 1 bar and its value using the former definition at 1 atm should be estimated.

Concept Introduction:

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 ${\text{(ΔG}}_{\text{f}}{}^{\text{°}}{\text{(O}}_2\text{(g))}\text{= 0)}$.

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.  The entropy changes associated with a phase transition reaction can be found by the following equation.

  $\text{ΔS }\text{}\text{=}\text{}\text{}\frac{\text{ΔΗ}}{\text{Τ}}$

Where,

  $\Delta {\rm H}$ 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