Question

Kp is the equilibrium constant for dissociation of the propionic acid dimer. what is the sign of the slope for a plot of the natural logarithm of kp vs. inverse temperature for this reaction?

Answer 1

Ans: The sign of the slope is negative

The free energy change (ΔG) is related to the equilibrium constant Kp as:

ΔG = -RTlnKp -------(1)

Also, ΔG = ΔH-TΔS ------(2)

therefore,

-RTlnKp = ΔH-TΔS

ln(Kp) = -ΔH/R(1/T) + ΔS/R

Thus, a plot of lnKp Vs 1/T will give a straight line with a negative slope such that:

Slope = -ΔH/R

Intercept = ΔS/R