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# Entropy of fusion and Enthalpy of fusion. Tweet

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1. Entropy of fusion and Enthalpy of fusion.
I am revising, doing a past exam paper and have this question which is confusing the crap out of me.

Calculate Entropy of Fusion @ 298K if we know
Enthalpy of Fusion is 36kJ/mol @ melting point of 424 K

And are also given molar heat capacities of Liquid = 33 J/K and solid = 17 J/K

I am muddling through with these two equations but can't figure out how to link them all together:

Sfusion = Hfusion/T

q = cDeltaT

The worst part is even if I get an answer I can't check if it's right because there's no past exam paper answers
2. Re: Entropy of fusion and Enthalpy of fusion.
I think you need to calculate delta H at 298k from Ht2 - Ht1 = delta Cp (T2 - T1), and then sub into the delta S equation you have quoted. The equation above comes from the equation of Cp, which is dh/dt.

I might be wrong, we usually seem to have different questions relating to entropy i.e. calculated the entropy change from a certain temperature to a different temperature, rather than calculate it at a specific temperature from an enthalpy change.
3. Re: Entropy of fusion and Enthalpy of fusion.
Oh, Kirchoff's law; it has the difference in heat capacities and the two temperatures... I don't know why I didn't see that earlier considering I've looked at it about 5 times.

I think we're on to a winner here. Thanks for that!

(Being stuck on this question has been seriously demotivating me, even though everything else has been going well I was left sitting thinking "WHY DID I CHOSE CHEMISTRY, I HATE CHEMISTRY.")
Last edited by JamHeadArt; 25-05-2012 at 11:32.