Rate constant in "catalysis" example

[KaushikMitra]

Dear GWB Team,

I attended GWB workshop in 2020 where we were given the 'catalysis' code to simulate Mn(II) oxidation on Fe(OH)3. I had a few doubts regarding the same:

1. How did we get the rate constant = 20000 ? Was it from a paper or just a number chosen for showing the process?

2. Why did we not include activation energy? Is it combined in the above number?

3. Why was Fe(OH)3(ppd) used? Can other minerals be used? 

4. How did we get the surface area of Fe(OH)3?

5. Why MnO2 (aq) has the log k = 9?

Thank you!