<span>Use the Arrhenius equation. Use p1 and p2 and T1 and T2 and solve for Ea (actgivation energy) in Joules, then plug that back into the Arrhenius equation and either p1 or p2 to calculate p at 25C.</span>
Depending if you were going up, you would be seeing an increase in relative ionization energies in a particular group on the periodic table, and vice versa, if you go down the group, an decrease in the relative ionization energies.
To determine the velocity of an object, you need to know the displacement and the change in time.
v = displacement / change in time
An ambient pressure of 1 atm