Van't Hoff Eq.

[Frenz Cabison 1B]

What does the Van't Hoff Equation exactly tell us? What do we use it for?

[Vasiliki G Dis1C]

The van't hoff equation is derived from setting the two expressions for ΔG equal to each other. The two expressions we have for ΔG are -RTlnK and ΔH-TΔS. If you set these equal and solve for lnK, you get lnK= -ΔH/RT + ΔS/R. This can be used to calculate the value of K at a different temperature if we know what the value of ΔH is. However, the form of the equation looks a little different in that case. It would be ln(K2/K1)=ΔH/R[(1/T2)-(1/T1)], to reflect the fact that you are dealing with 2 temperatures and 2 values of K. This equation proves that K is temperature dependent. Hope this helps!

[Niyanta Joshi 1F]

Van't Hoff equation accounts for the Le Chateliers Principle we learned earlier, it is useful to understand effect of temperature on equilibrium.