Answer::
Lower rate of reaction
Step-by-step explanation:
Lower concentration of reactant in an experiment is indicative of fewer ions or atoms present, which means a slower rate of reaction. In a titration reaction for instance, the end point would take longer to be substantiated, thereby increasing volume of titres. This is further backed up by collision theory which states that more particles in a system improves combinations of molecules.
This however may not be the case if the iodine in question is catalyst, in which case the change in concentration has no effect whatsoever on the reaction rte.
I hope this explanation fits the brief.