Why bromoethane are insoluble

Because only two layers form, two of the three substances are mutually soluble. we know that water and bromoethane are insoluble-they form two layers. From the reading, we know that hexane, a hydrocarbon, is insoluble in water. Thus, one layer is water and the other is a solution of hexane and bromoethane. If volumes are nearly additive, the hexane-containing layer will be the one with larger volume.