Answer:
The EMF and free enthalpy (or Gibbs Free Energy) of a reaction are directly related.
If the free enthalpy of a redox reaction is negative, then the EMF will be negative, indicating that the reaction is spontaneous and will occur without the need for an external source of energy.
If the free enthalpy of the reaction is positive, then the EMF will be positive, indicating that the reaction is not spontaneous and will not occur without the input of energy.
The relationship between free enthalpy and EMF is shown in the following equation:
∆G = -nFE°(cell), where n is the number of electrons transferred, F is the Faraday constant, and E° is the EMF of a cell under standard conditions.