Linear free energy relationships

[Horza2002]

Hi, can someone explain to me. or provide some good information on how a linear free energy relationship relates to a mechanism.

 

I have found one example where:

[CoX(NH3)5]2+ + H2O <--> [Co(NH3)5(OH2)] + X

 

If log (equi constant on the x axis) and log ( forward rate constant) on y-axis, the graph has a gradient of 1. It then goes onto say that this implies a dissociative mechanism....I just dont see how that applies