Van't Hoff Approach to Finding ∆H and ∆S

  • Thread starter ampakine
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  • #1
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Heres the question:
[PLAIN]http://img194.imageshack.us/img194/9042/vanthoff.png [Broken]
and heres the Van't Hoff equation (the form I like to use):
[PLAIN]http://img703.imageshack.us/img703/1577/vtequation.png [Broken]
I'm a bit confused about whats going on here. I see the formula includes ∆Ho, meaning the enthalpy change for 1 mole of reactant at 298K. Does that mean to use this formula T1 always has to be 298K? In other words to get the ∆Ho for the reaction would I just plug 298K into T1 and 4.25 x 10-7 into KT1 then plug any other pair of values from that table into T2 and KT2?
 
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Answers and Replies

  • #2
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The ∆H is always assumed to be constant with temp in this equation (standard enthalpy change), which is an obvious downside to the relation. If you derive it from
(d ln(K)) / (d 1/T) = -∆Ho/R you will find that from the integration.
 

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