Parameter in

thermodynamics which describes the 'favorableness' of a process.

The change in energy going from one state to another is expressed as:

###
*delta*G = *delta*H - T*delta*S

*delta*G - change in free energy

*delta*H - change in

enthalpy
*delta*S - change

entropy
**T **-

temperature
If

*delta*G is greater than zero, then the process is unfavorable and wont occur spontaneously. If less than zero, then the process will be spontaneous. If equal to zero, then the process is at equilibrium.

The change in free energy for a process where the

equilibrium constant (K) between the two state is known is expressed as:

###
*delta*G = -RT ln(K)

**R **- gas constant (8.31441

J K^{-1} mol^{-1})