My Math Forum Entropy Calculation

 Physics Physics Forum

 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
Newbie

Joined: Feb 2017
From: Lebanon

Posts: 18
Thanks: 1

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.

 Thread Tools Display Modes Linear 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

 Contact - Home - Forums - Cryptocurrency Forum - Top