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 February 16th, 2017, 12:39 AM #1 Newbie   Joined: Feb 2017 From: Lebanon Posts: 18 Thanks: 1 Entropy Calculation Can any one please help me to solve this? Calculate the entropy change if one mole of water evaporate at 373 K and 1 atm. If you look up the enthalpy of vaporization, for water in a table, you would get a molar enthalpy of 40.7 kJ/mol. February 17th, 2017, 06:05 AM #2 Senior Member   Joined: Apr 2014 From: Glasgow Posts: 2,142 Thanks: 726 Math Focus: Physics, mathematical modelling, numerical and computational solutions For the case of constant temperature: Change in entropy = Change in heat content / T $\displaystyle \Delta S = \frac{\Delta Q}{T}$ For latent heat transfer (evaporation): $\displaystyle \Delta Q = \Delta m \times l$ = 1 mole x latent energy per mole = 40700 J $\displaystyle \Delta S = \frac{\Delta Q}{T} = \frac{40700}{373} = 109.12$ J/K Thanks from JamSmith February 20th, 2017, 09:15 PM   #3
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Entropy Calculation

Quote:
 Originally Posted by Benit13 For the case of constant temperature: Change in entropy = Change in heat content / T $\displaystyle \Delta S = \frac{\Delta Q}{T}$ For latent heat transfer (evaporation): $\displaystyle \Delta Q = \Delta m \times l$ = 1 mole x latent energy per mole = 40700 J $\displaystyle \Delta S = \frac{\Delta Q}{T} = \frac{40700}{373} = 109.12$ J/K

Well I have another entropy related question, I was searching for material for more information about entropy conversions. I come to know about MM-PBSA Charmm, I read out some information and have some query related entropy conversion.

My question is:-

What is the conversion that charmm uses for convert the entropic units to kcal/mol? In the scripts I found the MM-PBSA script and I see that to obtain the entropy in kcal/mol only multiply by temperature, is that correct? That may implicated the 1 eu = 1kcal/mol.

Last edited by JamSmith; February 20th, 2017 at 09:24 PM. February 21st, 2017, 01:24 AM #4 Senior Member   Joined: Apr 2014 From: Glasgow Posts: 2,142 Thanks: 726 Math Focus: Physics, mathematical modelling, numerical and computational solutions I have no idea what CHARMM is, so I can'#t really answer your question, but the response to (presumably) your post here: https://www.charmm.org/ubbthreads/ub...at&Number=5712 seems correct. It's just the formula in my post; you're basically calculating heat from entropy. Tags calculation, entropy, entropy conversion Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post SophiaRivera007 Physics 2 January 13th, 2017 03:01 AM rocketman150 Advanced Statistics 1 October 5th, 2014 04:27 AM acepsut Economics 0 June 28th, 2013 04:28 AM iVenky Computer Science 1 March 27th, 2013 05:16 AM safyras Algebra 0 November 6th, 2011 01:50 AM

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