February 16th, 2017, 01:39 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, 07:05 AM  #2 
Senior Member Joined: Apr 2014 From: Glasgow Posts: 1,957 Thanks: 639 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 
February 20th, 2017, 10:15 PM  #3  
Newbie Joined: Feb 2017 From: Lebanon Posts: 18 Thanks: 1  Entropy Calculation Quote:
Well I have another entropy related question, I was searching for material for more information about entropy conversions. I come to know about MMPBSA 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 MMPBSA 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 10:24 PM.  
February 21st, 2017, 02:24 AM  #4 
Senior Member Joined: Apr 2014 From: Glasgow Posts: 1,957 Thanks: 639 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  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
conversion of entropy  SophiaRivera007  Physics  2  January 13th, 2017 04:01 AM 
entropy of combined events  rocketman150  Advanced Statistics  1  October 5th, 2014 04:27 AM 
How to compute entropy?  acepsut  Economics  0  June 28th, 2013 04:28 AM 
Entropy H is continuous in p(i)  iVenky  Computer Science  1  March 27th, 2013 05:16 AM 
calculating the entropy  safyras  Algebra  0  November 6th, 2011 01:50 AM 