Question

Some of the physical properties of H₂O and D₂O areas

follows:

Property	H2O	D2O
Density at 20oC(g/mL)	0.997	1.108
Boilingpoint (oC)	100.00	101.41
Meltingpoint(oC)	0.00	3.79
$\mathbf{∆}{{\mathit{H}}^{\mathbf{o}}}_{\mathbf{v}\mathbf{a}\mathbf{p}}\mathbf{(}\mathbf{k}\mathbf{J}\mathbf{/}\mathbf{m}\mathbf{o}\mathbf{l}\mathbf{)}$	40.7	41.61
$\mathbf{∆}{{\mathbf{H}}^{\mathbf{o}}}_{\mathbf{f}\mathbf{u}\mathbf{n}}\mathbf{(}\mathbf{kJ}\mathbf{/}\mathbf{mol}\mathbf{)}$	6.01	6.3

Account for the differences. (Note: D is a symbol often used for 2H, the deuterium isotope of hydrogen.)

Short answer

Density at 20⁰C(g/ml):

Density is higher in heavy water than in water because deuterium is heavy and has more molecular mass than water due to the presence of added neutrons.

Melting point:

D₂O shows a higher melting point than H₂O because of hydrogen bonding, known as the strongest intermolecular force. That's why D₂O needs more energy to break the bonds.

Boiling point:

D₂O shows a higher boiling point than H₂O because of the presence of hydrogen bonding, known as the strongest intermolecular force. That's why D₂O needs more energy to break the bonds

Enthalpy of vaporization

The enthalpy of vaporization mainly depends upon the intermolecular forces between the molecules. Of these two molecules, heavy water has a stronger intermolecular force than water.

Enthalpy of fusion

The enthalpy of fusion mainly depends upon the intermolecular forces between the molecules. In these two molecules, heavy water has a stronger intermolecular force than water.

Step-by-step solution

Water

As we all know, water is the lifeline of all living organisms on earth.

It is an inorganic, tasteless, and odorless substance essential for living organisms.

It is made up of 2 hydrogen atoms and one oxygen atom.

Water has a broader structure.

Heavy water

Deuterium is very much the same as normal hydrogen but contains an extra neutron, and heavy water is made up of two deuteriums and one oxygen.It is this extra neutron that adds to the weight of the atom, which makes it heavier.

Heavy water has a tetrahedral shape. It has a higher freezing point also.

Intermolecular force

Intramolecular forces are well-known forces that work between the molecules as they hold atoms of the molecule together within a molecule.Intermolecular forces exist between molecules of any compound, such as water molecules.

Explanation

Density at 20^oC (g/ml)

Density is higher in heavy water than in water because deuterium is heavy and has more molecular mass than water due to added neutrons.

Melting point:

D₂O shows a higher melting point than H₂O because of hydrogen bonding, known as the strongest intermolecular force. That's why D₂O needs more energy to break the bonds.

Boiling point:

D₂O shows a higher boiling point than H2O because of the presence of hydrogen bonding, known as the strongest intermolecular force. That's why D₂O needs more energy to break the bonds

Enthalpy of vaporization

The enthalpy of vaporization mainly depends upon the intermolecular forces between the molecules. In these two molecules, heavy has a stronger intermolecular force than water.

Enthalpy of fusion

The enthalpy of fusion mainly depends upon the intermolecular forces between the molecules. In these two molecules, heavy water has a stronger intermolecular force than water.