Question

why boiling and melting point of D2O is more than H2O???

Answer 1

So the boiling point of D2O is higher than H2O not because of the London forces, but because of the difference in electronegativity between the hydrogen and the water, creating an electrostatic attraction. ... Stronger hydrogen bond = stronger intermolecular forces = greater boiling point.

D2O have a higher boiling point then H2O because of the hydrogen bonding. Hydrogen bonds in deuterium oxide are slightly stronger than H2O . It is therefore, D20 requires more energy to excite the bonding electrons from the ground level to the dissociation point and a higher boiling point is observed.