Free Energy of Dissolution

Free Energy of Dissolution

  • The term dissolution refers to the process where a solvent, typically a liquid, breaks down a solute into its most basic parts, resulting in a solution.
  • This process can be either exothermic, where heat is released, or endothermic, where heat is absorbed.

Gibbs Free Energy (ΔG)

  • The Gibbs Free Energy concept is used to determine the spontaneity of a chemical reaction.
  • A reaction is likely to occur spontaneously if the final Gibbs Free Energy (ΔG) is less than zero (ΔG < 0). This indicates that the reaction will release energy, making it exothermic.
  • Conversely, a ΔG greater than zero (ΔG > 0) signifies an endothermic reaction that requires energy to proceed.
  • If ΔG is equal to zero (ΔG = 0), the reaction is at equilibrium.

Entropy (ΔS) and Enthalpy (ΔH)

  • The Gibbs Free Energy (ΔG), can be calculated using the formula: ΔG = ΔH - TΔS
  • Here, ΔH is the change in enthalpy or total energy, T is absolute temperature in Kelvin, and ΔS is the change in entropy or disorder of the system.
  • A positive ΔS (ΔS > 0) means there is an increase in disorder (common in dissolution), while a negative ΔS (ΔS < 0) means there is a decrease in disorder.
  • ΔH > 0 denotes an endothermic process, while ΔH < 0 represents an exothermic process.

Free Energy of Dissolution

  • The Free Energy of Dissolution is the total free energy change (ΔG) when a solute is dissolved in a solvent.
  • It incorporates both entropy and enthalpy changes: the breaking of bonds in the solute and solvent (ΔH of dissolution), as well as the increased disorder when a solute dissolves (ΔS of dissolution).
  • A negative ΔG indicates that the dissolution is spontaneous and exothermic, while a positive ΔG indicates that dissolution is not spontaneous and is endothermic.
  • At equilibrium, ΔG of dissolution equals zero, and the concentration of the solute in the solution will not change further.

Significance

  • Analysis of the free energy of dissolution can be used to predict whether a substance will dissolve spontaneously in a given solvent.
  • It can also help us understand and control industrial processes involving dissolution, such as the creation of solutions in chemical or pharmaceutical industries.