Answer:
Aqueous (water) layer
Step-by-step explanation:
If water and hexane are mixed, the to liquids separate into two immiscible layers; an organic layer and an aqueous layer.
The organic layer will remain at the top, while the aqueous layer will remain below.
Ions can mostly be found in the aqueous layer, hence the aqueous (water) layer will have a higher concentration of the I3^- ion.