Spontaneity: Gibbs Free Energy
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Gibbs
Free Energy (G) is used most often to determine if a reaction is
spontaneous or not:
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ΔG
negative →
Spontaneous reaction
ΔG = 0 at equilibrium
ΔG positive → Non-spontaneous reaction
We can use ΔH and ΔS to determine whether or not a reaction is spontaneous. Remember that T (in K) is always positive. For a spontaneous reaction, ΔG < 0:
ΔG = 0 at equilibrium
ΔG positive → Non-spontaneous reaction
We can use ΔH and ΔS to determine whether or not a reaction is spontaneous. Remember that T (in K) is always positive. For a spontaneous reaction, ΔG < 0:
If
ΔH is negative and ΔS is positive, this will ALWAYS be the case,
since a negative number is always less than a positive number.
If ΔH is positive and ΔS is negative, this will NEVER be the case, since a negative number is never greater than a positive number.
If ΔH is positive and ΔS is negative, this will NEVER be the case, since a negative number is never greater than a positive number.
