Software to predict equilibrium products in the ideal gas phase

I'm interested in software packages that can answer the following kind of question:


* If I mix 30mol% $N\_2$ and 70mol% $H\_2$ together at 2 bar and 2000C, what is the equilibrium composition after all reactions have reached equilibrium. Assume all reactants and products are ideal gases.


This is a relatively straightforward calculation. All that is required is knowledge of standard Gibbs Free Energies of formation and specific heat capacities for each species which may be formed. Of course, the challenge is guessing *which* species may be formed - here an obvious candidate is $NH\_3$, but it is certainly possible that the formation of other species could lead to a lower value of the Gibbs Free Energy. A software package with a large database of standard Gibbs Free Energies and ideal gas heat capacities would be very useful here - you could simply select to search over all chemicals which you suspect may be formed, or instead you could minimise the Gibbs Free energy over 'all substances in the database' (at least those composed of the available chemical elements - $N$ and $H$ in this case.) 


Does anyone know of any software packages (open source or otherwise) which could do these calculations?


