12-4-free-energy_summary

The learning objective is to understand the concept of Gibbs free energy (G), its relation to spontaneity, and how to calculate free energy change for a chemical process. Free energy (G) is defined as a system’s enthalpy (H) and entropy (S) at constant temperature and pressure, and the change in free energy (ΔG) can be calculated using the following equation: ΔG = ΔH - TΔS where ΔH is the enthalpy change, ΔS is the entropy change, and T is the temperature in Kelvin. The sign and magnitude of ΔG provide information about the spontaneity of a process: - If ΔG < 0, the process is spontaneous. - If ΔG > 0, the process is nonspontaneous or needs an external input to proceed. - If ΔG = 0, the system is in equilibrium. Free energy change can also be calculated using enthalpies of formation (ΔHf) and the entropies of reactants and products. Using standard enthalpies and entropies from a thermodynamic data compilation, the standard free energy change (ΔG°) can be computed as follows: ΔG° = ΔHf° - TΔS° Free energy is significant because it indicates the amount of useful work a spontaneous process can accomplish, with more negative values of ΔG signifying greater achievable work. The computing of work from free energy is a more advanced topic that is not covered in this summary. In conclusion, the Gibbs free energy is an essential concept in thermodynamics, as it provides a means to predict the spontaneity of chemical and physical processes and the potential work these processes may produce.