Delta H

$\Delta G^{\circ}= \Delta H^{\circ} - T \Delta S^{\circ}$

$\Delta G^{\circ}= -RT\ln K$

$\Delta G^{\circ}= \sum \Delta G_{f}^{\circ}(products) - \sum \Delta G_{f}^{\circ}(reactants)$

Rafsan Rana 1A
Posts: 55
Joined: Sat Aug 24, 2019 12:16 am

Delta H

I forgot what Dr. Lavelle said in lecture, but it was something about delta H or the change in enthalpy doesn't change even if temperature changes? Can someone explain exactly what he said and what it means?

Ashley Wang 4G
Posts: 103
Joined: Wed Sep 11, 2019 12:16 am

Re: Delta H

I think this is from using Van't Hoff's equation to calculate K at a different temperature if ∆Hº is known.
We assume the difference in entropy ∆Sº between the reactants and products in a reaction is the same even when the reaction occurs at two different temperatures. Even though the actual entropy values will be different at different T's, the change between them is assumed to be the same and thus not temperature-dependent. The same is assumed for ∆Hº.

This allows us to get the equation ln(K2/K1) = ∆Hº/R (1/T2 - 1/T1) from Van't Hoff's equation. Hope this is helpful! Sorry the equation looks like a mess in this layout.