00:01
To calculate the temperature below which the process is spontaneous, we need to set delta g equal to zero.
00:09
Delta g is equal to delta h minus t delta s.
00:17
So if delta g is zero and our delta h is negative 70 .0 kilojoules, we'll subtract off t.
00:26
Will be solving for t and negative 0 .40 kilojoules per kelvin and t is 175 kelvin.
00:44
So below 175 kelvin, the process would be spontaneous with the negative delta g.
00:57
To determine the melting point, we carry out a similar calculation.
01:02
A melting point is an equilibrium point.
01:04
Where freezing and melting occur at equal rates.
01:10
Therefore, delta g is also zero.
01:12
So if we know delta h fusion and delta s fusion, at the melting point, delta g is zero, we can calculate the melting point temperature.
01:23
Delta h is 24 .32 kilojoules.
01:32
We'll then subtract off t and delta s, 83 .93 .93 joules per kelvin mole.
01:40
Converted to kilojoules is 0 .083 .993 kilojoules per kelvin mole.
01:49
We need both of these in the same energy units.
01:53
Then when we solve for t, we get to 89 .8 kelvin to 89 .8.
02:09
To have a standard gives free energy of formation equal to zero...