Gibb's Free Energy

[Guillermo Vega 1H]

Do Gibb's Free Energy and Enthalpy/Entropy relate in any way? If so, then how? And if they do not relate, then what are their differences?

[Ryan Doyle 3E]

delta G (the change in gibb's free energy) = delta H of reaction - Temperature x delta S (entropy of reaction)

[Nick_OConnell_2F]

Hi Guillermo,

Gibbs free energy, enthalpy, and entropy are all entirely related! Foremost, they are all energy terms and can thus be subtracted from each other to find available energy. Defined, Gibbs free energy is the amount of energy freely available for a system to do work. This is calculable after taking into consideration enthalpy of a reaction (which we know is the energy absorbed/released during a reaction) and entropy of a reaction (which we know is the measure of the disorder/randomness of energy in a system).

Gibbs free energy is always considered when a system reaches chemical equilibrium at constant temperature and pressure:


The value of the change in Gibbs free energy can give you insight into the spontaneity of a reaction, or the ability of a reaction to take place with out the addition of external energy. However, it is not the absolute value that gives you your answer, but rather the change (sign). A negative Gibbs free energy indicates that a reaction can occur spontaneously, which is favorable in nature. Thus, coming back to your original question, the values of enthalpy and entropy have a direct effect on the value of and likewise help determine the spontaneity of a reaction.