Entropy and Gibbs Energy

Understanding Entropy and Gibbs Energy


  • Entropy is a measure of disorder or randomness in a system.
  • Denoted by S, entropy is used to help describe the direction of spontaneous reactions.
  • High entropy signifies a more disordered system, whereas low entropy indicates a more ordered system.
  • Entropy increases during processes that lead to a greater dispersal of energy and matter, such as in dissolving substances, mixing gases, or heating an object.

Gibbs Free Energy

  • Gibbs Free Energy (G) is the maximum amount of non-expansion work that can be extracted from a closed system.
  • It considers both the system’s enthalpy (H) and entropy (S) at a constant temperature (T): G = H – T*S.
  • A negative change in Gibbs Free Energy (∆G) indicates a spontaneous reaction, while a positive ∆G indicates a non-spontaneous reaction.

Spontaneity of Reactions

  • The spontaneity of chemical reactions can be predicted using Gibbs Free Energy (∆G).
  • If ∆G is negative, the reaction will happen spontaneously under the given conditions.
  • If ∆G is positive, the reaction is not spontaneous, but it may occur by providing energy (like heating).

Entropy, Gibbs Energy in Industry

  • The concepts of entropy and Gibbs Free Energy are crucial in industrial chemistry.
  • Predicting reaction spontaneity is key to process safety and efficiency in chemical manufacturing.
  • Understanding ∆G can aid in the design of industrial processes that are energy efficient and environmentally sustainable.
  • Control of reaction conditions to favour spontaneous, exothermic reactions can help minimise energy costs.