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From: waterman@engg.ucalgary.ca (jason waterman)
Newsgroups: comp.sys.handhelds
Subject: RE:  EQ LIB Question
Message-ID: <9104052337.AA02441@engga>
Date: 5 Apr 91 23:37:54 GMT
Lines: 63
Return-path: <waterman@engg.ucalgary.ca>
To: handhelds@gac.edu

Hi there,

In a previous article, Conrad wrote:

>     Hi,
>        In the equation library ROM the specific heat for atomic oxygen
>        is listed as .92 J/(g*K). A reliable source ( supposedly a man
>        from HP in Switzerland) phoned me up after I had made some enquiries
>        as to the meaning of this number, and told me it was the specific
>        heat at constant pressure (i.e. Cp). I have just found out
>        that in the J.A.N.A.F. tables the specific heat at constant
>        pressure for atomic oxygen is listed as 22.74 J/K/mol. Lets
>        do some conversions....
>
>          for O 22.74 J/K/mol is equivalent to 1.421 J/(g*K).
>
>         Hmm me thinks something not right,
>
>          for O 0.92 J/K/mol is equivalent to 14.72 J/(K*mol).
>
>         This is equivalent to a 35% discrepancy. This
>         is rather fundamental to me since I do Atmospheric modelling
>         and one of the important parameters is the specific heat
>         capacity of atomic oxygen at constant pressure.
>
>             So could a nice kind HP person reading this possibly put me
>         right? I would be very grateful.
>
>               Thanks
>
>                  Conrad
>
>        P.S. The J.A.N.A.F. tables come from the National Bureau of standards


I'm not from HP, but I did some checking and found the same value of
.92 J/(g*K) in two sources,  my thermodynamics text and the CRC handbook of
Chemistry and physics.  I also found that this was the value of Cpo which is
defined as the zero-pressure constant-pressure specific heat.  The values I 
found were for Oxygen Gas O2, so this could be the problem.  The difference
could also be due to the fact that the 0.92 J/(g*K) is for zero-pressure and
further calculations are necessary to obtain the Cp value for the pressure
you are working at.  Maybe someone more familiar with thermodynamics could
elaborate, since I'm not finished the course yet.  Also, I believe that
there is an error in the units you gave for your value of specific heat of 
Oxygen.  You gave the value of 22.74 J/K/mol.  I think that it should be
22.74 J/(mol*K). 

Hope this helps.
 
P.S.

>          for O 0.92 J/K/mol is equivalent to 14.72 J/(K*mol).
                      ^?    ^?

I'm wondering how you managed that conversion.  Shouldn't it be 0.92 J/(g*K)?


-------------------------------------------------------------------------------
Jason Waterman
The University of Calgary
Calgary, Alberta, Canada
Email: waterman@engg.ucalgary.ca
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