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### Gibbs

Posted: Thu Feb 21, 2019 7:44 pm
Could someone explain to me in words (to help me conceptualise) what Gibbs Free energy is?

### Re: Gibbs

Posted: Thu Feb 21, 2019 9:22 pm
Gibbs Free energy helps us calculate the energy that is free to do work after a certain process. This does not include the energy in between electrons or protons, but it is the energy that can be transferred to do, for example, expansion against a force.

### Re: Gibbs

Posted: Thu Feb 21, 2019 9:38 pm
It is the energy available to do work, which determines spontaneity of a reaction because a negative value of delta G means the reaction is spontaneous, while a positive value means it is not spontaneous.

### Re: Gibbs

Posted: Thu Feb 21, 2019 9:55 pm
Gibb's Free Energy can be calculated through using enthalpy and entropy.
deltaG=deltaH - T*deltaS

When a reaction has a positive enthalpy (+deltaH):
deltaG will be positive if entropy is negative (-deltaS)
deltaG will be negative if entropy is positive (+delta S) and T*deltaS is greater than deltaH

When a reaction has a negative enthalpy (-deltaH):
deltaG will be positive if entropy is negative (-deltaS) and T*deltaS is greater than deltaH
deltaG will be negative if entropy is positive (+deltaS)

When a reaction has a positive deltaG, then it is not spontaneous because it means the products has more free energy than the reactants (an input of free energy is needed).
When a reaction has a negative deltaG, then it is spontaneous because it means the products has less free energy than the reactants (free energy is released).