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What is Spontaneity and Gibb's free energy?
Question Date: 2004-05-11
Answer 1:

Gibb's Free energy is one measure of the energy that is available (measured at constant temperature and pressure) to transform one chemical compound to another, or one phase to another (liquid to solid ...) or to perform a chemical reaction. When you write a general process of transformation:

A --- > B

>And if you perform the transformation at constant temperature and pressure, and if the product B has a smaller free energy than the reactant A, the transformation can proceed on its own (spontaneously).

Answer 2:

The Gibbs Free Energy is a quantity that represents the preferred energy state of a reaction. The relative Gibbs Free Energies of two states determines how much of each there will be, and if one has a lower G.F.E. than the other, it will be more common.

Thus, for instance, the carbon dioxide in a can of soda has two possible states that it can be in: in solution (dissolved), or as a gas (bubbles).

Under the pressure inside the can, the conditions favor the carbon dioxide being in solution. When you open the can, the GFE is much lower for the carbon dioxide to be a gas, so it fizzes out as bubbles. Gas is continually being dissolved back into the soda just as gas is coming out as bubbles, even in a glass of water. The higher the GFE of dissolved gas relative to that of gas, the lower will be the rate at which gas dissolves and the faster the rate of which gas will form bubbles.

Answer 3:

In college chemistry I learned that Gibbs Free Energy is the same as Free Energy, and we should call it Gibbs Free Energy in the U.S. because Gibbs was an American. Gibbs Free Energy is a number that tells whether a chemical reaction or process will occur and how stable the product(s) will be, based on 2 other thermodynamic properties - entropy and enthalpy - and temperature.

Spontaneity appears to refer to whether the reaction will occur or not. Some (most??) reactions spontaneously go in one direction but not the other.

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