Statement I is true. Because of closer proximity
(1,2-positions) of
−OH and
−NO2 groups, o-nitrophenol shows intramolecular hydrogen bonding.
So, o-nitrophenol exists in monomeric state and becomes steam volatile.
Statement II is false, because, due to the presence of intramolecular hydrogen bonding, boiling point and melting point of o-nitrophenol will be lower.
Note p-nitrophenol is the positional isomer of o-nitrophenol.
p-nitrophenol shows intermolecular hydrogen bonding and so, it has higher boiling point, melting point and water solubility.