## When to use Van't Hoff equation

$\ln K = -\frac{\Delta H^{\circ}}{RT} + \frac{\Delta S^{\circ}}{R}$

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KarineKim2L
Posts: 100
Joined: Fri Aug 30, 2019 12:16 am

### When to use Van't Hoff equation

How can we assume that the standard delta H and standard delta S are constant when deriving the Van't Hoff equation? Do these values not differ with temperature?

John Liang 2I
Posts: 102
Joined: Fri Aug 30, 2019 12:18 am

### Re: When to use Van't Hoff equation

KarineKim2L wrote:How can we assume that the standard delta H and standard delta S are constant when deriving the Van't Hoff equation? Do these values not differ with temperature?

Lavelle mentioned in class that although having a higher temperature will indeed increase the initial and final H and S values, the change of H and S will remain constant since both values (final and initial) will increase the same amount. Since these are state functions, that's why we can assume constant delta H and S despite different temperatures. hope it helps!

Rory Simpson 2F
Posts: 106
Joined: Fri Aug 09, 2019 12:17 am

### Re: When to use Van't Hoff equation

The changes in $\Delta S^{\circ} and \Delta H^{\circ}$ are generally negligible with a change in temperature so we just assume that they are constant when deriving (delta G, on the other hand, does change significantly with temperature changes).

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