We can calculate the value of the standard state enthalpy change, Ho,
and the standard state entropy change,
So,
for a chemical change from measurements of the equilibrium constant for
the change at several different temperatures.
Calculating Enthalpy Changes and Entropy Changes from the Change in Keq with Temperature
To determine Ho
and
So,
plot ln Keq vs 1/T. The resulting straight line
will have a slope equal to -
Ho/R
and an intercept equal to
So/R.
The derivation for this relationship follows:
We have seen that | |
and | |
Thus we can write | |
or | |
This last equation is the equation of a straight line with a a slope of
-Ho/R
and an intercept equal to
So/R.