Re: CCL:SUMMARY:Equilibrium Constants

Dear Everyone:
Many people have communicated to say that they can't hook up to the NASA Glenn CEA site referenced below because the link was not working:  the link should have been without the final character, use :

Others have commented about the convenience of the PFC program for obtaining thermodynamic functions and have asked for details about its input data.  The CEA database consists of blocks of coefficients to the following 'Shomate plus" equation:

Cpo (T)/R  = a1T-2 + a2T-1 + a3 + a4T + a5T2 + a6T3+ a7T4  

plus integration constants for H and S. This form was chosen because it allows accurate fits over a wide temperature range.  Input data is taken from standard compilations, from the literature, or calculated from published spectroscopic data.  The data are updated almost continuously and documented thoroughly. 

CEA and its database are heavily used by the aerodynamics communiity for rocket and jet engine design and analysis, and the database has grown from 42 species in its first published version (in 1951) to the current 2000.  Much of this information is contained at

Also soon available will be  a report  NASA/TP-2002-211556, available from Ms.McBride at the above site.

At 03:28 PM 08/08/2002 -0400, knauerc wrote:
Thanks to everyone for your help, and my apologies for being
so late in posting this summary of responses.

My question was:

Does anyone know where I can find good data for the equilibrium
constants, (as a function of temperature), for the reactions:

H2 + Cl2 = 2HCl


H2 + Br2 = 2HBr

The answers I received were:

1) Abhishek Jha (ajha (- at -)

I have used this before so I am sure you will get what you are looking
for.  Best of luck!

Abhishek Jha

2) Wayne Steinmetz (WES04747 (- at -)

Consider using the JANF Thermochemical Tables.

3) Bill Smith (bilsmith (- at -)

Apart from standard tables like the JANAF Tables
(CHASE,M.,Jr.,1998, {\it NIST-JANAF Thermochemical Tables, 4th ed., J. Phys. and
Chem. Reference Data Monograph No. 9,} (Am. Chem. Society, Am. Inst.
Physics).Data, you can get a lot of this data from the free Lite version of the
reaction equilibrium software package EQS4WIN, available at

4) Chuck McFarland (cwm001 (- at -)

Given that enthalpy and entropy easily lead to free energies, which in turn lead
to equilibrium constants, and that Shomate equation coefficients give
temperature dependence, most, if not all, of what you need is at

5) David Shobe (dshobe (- at -)

The NIST WebBook ( has thermochemical data as
a function of temperature, and you can calculate equilibrium constants in the
usual way.

(Also note that the answers and necessary data sets will differ considerably for
gas-phase and aqueous-phase equilibrium constants).

6) Viswanathan Balakrishnan (bviswan (- at -)

The equilibrium constants can be calculated from the thermodynamic data
available at

7) Michael J. Zehe (Michael.J.Zehe (- at -)

A convenient source of up-to-date thermodynamic data in an easily-used form is
the program PFC, at PFC allows the user to get
accurate data for over 2000 species contained in the NASA Glenn, (formerly NASA
Lewis),database documented in NASA TP-2002-211556 and at
http://www>>. This database has been maintained and
documented for almost 50 years by Ms. Bonnie Mcbride et al at NASA Glenn in
support of the NASA chemical equilibrium program CEA.

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Michael J. Zehe
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