Chapter 10, Problem 10B.2ST

Interpretation Introduction

Interpretation:

The molar energy required to reverse the orientation of the dipole moment of the water molecule if the lithium ion and a water molecule is separated by $\text{300}\text{nm}$ has to be given.

Concept introduction:

Polar molecules are the molecules having a positive and negative end and so there will be a charge separation.

A polar molecule is a molecule where the polar bonds are asymmetrically arranged (the dipoles do not cancel)

A nonpolar molecule is a molecule with no polar bonds or a molecule where the polar bonds are symmetrically arranged.

In polar molecule the charge separation occurred with respect to the difference in electronegativity of atoms in the molecule.

Calculation of the energy of interaction of a point charge and a dipole:

$\begin{array}{c}\text{V}\left(\text{r}\right)\text{=}-\frac{{\mu }_1{\text{Q}}_{\text{2}}}{{\text{4πεr}}^2}\\ \\ {\text{μ}}_{\text{1}}\text{-}\text{Dipole}\text{moment}\\ {\text{Q}}_{\text{2}}\text{-}\text{Charge}\\ \text{r-}\text{Separation}\\ \text{ε}\text{-}\text{Permittivity}\text{of medium}\\ \end{array}$

  $\begin{array}{l}\text{ε}\text{=}{\text{ε}}_{\text{r}}{\text{ε}}_{\text{0}}\\ \\ {\text{ε}}_{\text{r}}\text{-}\text{Relative}\text{permittivity}\\ {\text{ε}}_{\text{0}}\text{-}\text{Vacuum}\text{permittivity}\\ \end{array}$