N2O difference in electronegativity

It has zero dipole moment. Two N atoms in nitrogen molecule have zero electronegativity difference. The bond pairs of electrons are equally distributed between two N atoms.

(Missing in the question):
-NH4Cl, ammonium chloride soluble in water, insoluble in Hexane.
-C10H8, naphthalene insoluble in water, soluble in Hexane.
-C2H5OH, ethanol soluble in water, soluble in Hexane. 
-CO(NH2)2, urea soluble in water, insoluble in Hexane.
While Hexane is anon polar solvent and water is a polar solvent,
So your answer is C10H8 naphthalene
C10H8(as a non-polar ) so it forms a layer in the water (which is a polar solvent) and at Hexane (which is a non-polar solvent)so C10H8 will dissolve in it.