In one form, the natural log of the "pre-exponential factor" A provides an intercept of the graph formed by plotting the natural log of k against 1 over T, producing a straight line with gradient given by the negative of the activation energy divided by the gas constant.  
The existence of the "pre-exponential factor" in this equation results from the fact that the collision rate is only weakly dependant on temperature, allowing one to treat as a constant its product with the steric factor.  In one form, the natural log of the "pre-exponential factor" A provides an intercept of the graph formed by plotting the natural log of k against 1 over T, producing a straight line with gradient given by the negative of the activation energy divided by the gas constant.  FTP, what is this equation concerning the rate constant, developed by the winner of the Nobel Prize for Chemistry in 1903?
The existence of the "pre-exponential factor" in this equation results from the fact that the collision rate is only weakly dependant on temperature, allowing one to treat as a constant its product with the steric factor.  
Arrhenius equation