Question

can someone kindly explain thermodynamic potential to me.

Answer 1

ya good one....

Answer 2

Do you mean chemical potential, often given the Greek letter mu as a symbol? If so, chemical potential is the potential energy resulting from the ability of compounds to chemically react. If a given reaction is very likely to proceed, and the reverse reaction less so, then the reactants have a higher chemical potential than the products. This is no different from the fact that water at a higher elevation has a higher mechanical potential energy than water at a lower elevation. The water will flow downhill if given the chance, so it has a higher potential energy. In the same way, chemical reactants will "flow downhill" towards products if they can, so they have a higher chemical potential energy. The only part that is odd about this is that you can readily identify the force that gives water at a high elevation its higher energy: the force of gravity pulling the water molecules downward. What is the equivalent force in the chemical situation? To some extent, it's the complex set of electrostatic and quantum forces that impel atoms to form bonds with each other. But there is also an entropic component, which isn't a force at all, in the usual sense of the word, but which in this context has equivalent results. (That is also why chemical potential is related to free energy, not mechanical energy.)

I should also add that the presence of the entropic contribution means the chemical potential applies even if the "chemical reaction" involved is just a physical change of state, e.g. H2O(g) -> H2O(l), or even just a change in volume, temperature or pressure, e.g. H2O(g,150C) -> H2O(g,200C). These aren't always considered "chemical reactions" but from the point of view of thermodynamics, changes in temperature and pressure are no different than changes in mole number.