Chapter 4, Problem 4A.2E

Interpretation Introduction

Interpretation:

More stable allotrope of carbon (diamond and graphite) has to be predicted using their given standard Gibbs energy of formation.

Concept introduction:

Free energy (Gibbs 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

Gibb’s energy is an important factor which greatly affect the thermodynamic stability of a molecule or compound.

For example:  when state A is said to be more thermodynamically stable than state B of a chemical system, if the Gibbs energy of the change from A to B is positive.

The stable state of the chemical system is taken as its reference state.

The substance with lower molar Gibbs energy is more stable.