The boiling point of p-nitrophenol is higher than that of o-nitrophenol because:
1
NO2 group at p-position behaves in a different way from that at o-position
2
Intramolecular hydrogen bonding exists in p-nitrophenol
3
There is intermolecular hydrogen bonding in p-nitrophenol
4
p-nitrophenol has a higher molecular weight than o-nitrophenol