Question

does FeCl3 disassociate in water? if so why?

Answer 1

I cant wrap my head around why in a FeCl3+KI reaction, FeCl3 doesnt affect the rate reaction (determined empirically)

Answer 2

FeCl3 is very soluble (from wikipedia 74.4 g/100 mL in water at zero degrees). It will dissociate because it's energetically favourable.

Answer 3

maybe in the reaction FeCl3 is not involved in the rate-determining step, or, maybe it's concentration, in the conditions you used, is so high that it can be disregarded because it's effectively constant.