Thermodynamic potentials
In
thermodynamics, four different quantities, measured in units of
energy, are called
thermodynamic potentials:
where
T =
temperature,
S =
entropy,
p =
pressure,
V =
volume
Chemical reactions
Changes in these quantities are useful for assessing the degree to which a chemical reaction will proceed. The relevant quantity depends on the reaction conditions, as shown in the following table. (NB "Δ" denotes the change in a quantity.)
| Constant V | Constant p |
Constant S | ΔU | ΔH |
Constant T | ΔF | ΔG |
Most commonly one considers reactions at constant p and T, so the Gibbs free energy is the most useful potential in studies of chemical reactions.
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