[biostu]

The pre-exponential factor for the reaction

H2 + I2 = 2HI

Is 10^11 L mol^-1 s^-1, and the activation energy is 165 kJ mol^-1 in the range 300 to 500°C.  If the collision diameter is 320 pm, what value of the pre-exponential factor is expected from collision theory at 600 K, and what is the value of the steric factor p?

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Thoughts:

I know the Arrhenius equation and the rate constant formula for a bimolecular gas phase reaction, as predicted by collision theory:

http://en.wikipedia.org/wiki/Collision_theory

I also know k = 2d^2 N sqrt(piRT / M), where N is avogadro's number.

I have been at this problem for hours and can't seem to make any progress.  I am not sure what to use for M (should I use only the mass of I2 since its so much bigger than hydrogen?) Once I solve for k, how can I solve for both Z and p without having either to plug into the equation? Are these even the correct formulas for this problem? I'm pretty sure the activation energy remains 165 kJ/mol, but this is as far as I've gotten.

Unfortunately, this is a new chapter and I was absent the day we went over collision theory.

I know the pre-exponential factor answer is 4.87 x 10^11 L/mol/s and the steric factor is .21.

Any help would be much appreciated.  Thank you.