## Spontaneity: Gibbs Free Energy

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.