Gibbs free energy represents the amount of energy absorbed or released by a chemical reaction that is available to do work. It is defined as the change in enthalpy minus the temperature multiplied by the change in entropy. A chemical reaction will be spontaneous in the forward direction if the gibbs free energy is negative, or spontaneous in the reverse direction if the gibbs free energy is positive.
Enter any three variables out of enthalpy, temperature, entropy, and Gibbs free energy to calculate the missing fourth variable: