The relationship between Gibbs free energy and spontaneity is that a process or chemical reaction is spontaneous if the change in Gibbs free energy (ΔG\Delta GΔG) is negative. Conversely, if ΔG\Delta GΔG is positive, the process is non-spontaneous, and if ΔG=0\Delta G=0ΔG=0, the system is at equilibrium.

Explanation of Gibbs Free Energy and Spontaneity

• Gibbs free energy (GGG) is a thermodynamic quantity defined as G=H−TSG=H-TSG=H−TS, where HHH is enthalpy (total heat content), TTT is absolute temperature in Kelvin, and SSS is entropy (degree of disorder).
• The change in Gibbs free energy for a process is given by ΔG=ΔH−TΔS\Delta G=\Delta H-T\Delta SΔG=ΔH−TΔS, where ΔH\Delta HΔH is the change in enthalpy and ΔS\Delta SΔS is the change in entropy.
• A negative ΔG\Delta GΔG means the process releases free energy that can do work, indicating spontaneity.
• A positive ΔG\Delta GΔG indicates the process requires energy input to occur and is non-spontaneous.
• At ΔG=0\Delta G=0ΔG=0, the system is at equilibrium and no net change occurs.

Intuitive Understanding

• Spontaneity in chemistry means that a process can happen without external input of work.
• Negative Gibbs free energy signifies that the process increases the entropy of the universe overall, despite changes in the system entropy.
• This is the key criterion for determining if a reaction or process is feasible under constant temperature and pressure conditions.

In summary:

ΔG\Delta GΔG Value| Process Behavior
---|---
ΔG<0\Delta G<0ΔG<0| Spontaneous process
ΔG>0\Delta G>0ΔG>0| Non-spontaneous process
ΔG=0\Delta G=0ΔG=0| System at equilibrium

This relationship is fundamental in predicting and understanding chemical reactions and physical processes in thermodynamics.