Question

Melting point, enthalpy of vapourisation and viscosity data of $H_{2}O$and $D_{2}O$ is given below:

	$H_{2}O$	$D_{2}O$
Melting point / K	373.0	374.4
Enthalpy of vapourisation at (373 K)/ kJ $mo{l}^{-1}$	40.66	41.61
Viscosity/centipoise	0.8903	1.107

On the basis of this data explain in which of these liquids intermolecular forces are stronger?

Answer 1

• Melting points depends on the energy required to overcome intermolecular forces, holding them in lattice. So, the molecule having higher melting point would have stronger intermolecular forces.
• The molecule having higher heat of vapourisation will have stronger intermolecular forces in it’s liquid state. Thus, it will take higher energy to change from liquid to vapour state.
• The molecule having higher viscosity would have higher intermolecular forces too.

From melting point, enthalpy of vaporization and viscoity data of $H_{2}O$ and $D_{2}O$, we can conclude that $D_{2}O$ has stronger intermolecular forces as compared to $H_{2}O$ because their values are higher for $D_{2}O$as compared to those $H_{2}O$.