Can someone show me how to do this?

Question

Below 800 K, dimerization of C2F4 to cyclo-C4F8 follows 2nd order kinetics with k = 10^11.07 exp (-107 kj/mol/RT) cm^3 mol^-1 sec^-1. The molecular diameter of C2F4 is 5.12 A. Calculate k by collision theory and determine steric factor at 725 K.
Please show me how to do this!!!

Answer 1

sorry. no idea!!

Answer 2

You are missing a couple of things here which would allow you to do this problem. (You need to get the activation energy of the reaction AND the reaction cross-section.)

Firstly, you need to calculate the collistion frequency, Z. To do this you can use the following relationship:

Z = Na*B* SQRT(8*kb*T/Pi*uab)

Z = Collision Frequency
Na= Avogadro's number
B = Reaction Cross Section
kb= boltzmann constant
T = Temperature
uab = reduced mass of reactants

Based on the information you placed in your question, it would be helpful to get obtain the reaction cross section AND calculate the reduced mass of the reactants. (Since this is junior or senior level question, I assume you remember how to calculate the reduced mass of reactancts.)

Once you have this, you can NOW use the "Z" value you calculated as an input for the equation below:

k(T) = Z *(p)*Exp(-Ea/RT)

You have the rate constant already. If you were able to calculate the Z, you have that also. What you are being asked to calculate is p, the steric factor. In this case, you need to know what the activation energy is for the reaction.

In all, once you get the activation energy, Ea, and the reaction cross section, you should be able to do this problem. (I hope those values were given to you.)

Let us know how it works out for you and pay attention to your units.