Create the equation of a line by substituting delta G=delta H-TdeltaS into the equation delta G= -RT ln(Kc), and solve for ln(Kc)
ΔG = -RTlnKc -----(1)
and
ΔG = ΔH – TΔS -----(2)
The Equation 1 and 2 can be combined to obtain the Equation 3 as follows:
-RTlnKc = ΔH – TΔS ------- (3)
Reorganization of Equation 3 yields Equation 4, which shows the linear relationship between lnKsp and 1/T:
lnKc = − ( ΔH/R ) ( 1/T ) + ΔS/R ----------(4)
Therefore, a plot of lnKc versus 1/T yields a straight line with a slope of –ΔH/R and a y-intercept of ΔS/R. So the ΔH and ΔS can be calculated based on the linear equation obtained from the linear fitting of the graph.
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