Question

4. (20) Polarizability and dielectric constant Benzene at 20 °C has an electronic polarizability Qo = 47 x 10.3 x 10-30 m", a density Pm = 880 kg/m", and a molecular mass of 78.1 g/mol. Benzene does not have a per- manent dipole moment. Chloroform ( CHCl3 ) at 20°C has an electronic polarizability Oto = 471 X 8.2 x 10-30 m', a density Pm = 1480 kg/mº, and a molecular mass of 119.4 g/mol. Chloroform has a dipole moment po = 1.06 D. Note: Jackson uses the notation /mol = a and Yol = 00. (a) Calculate the dielectric constant of benzene at 20 °C and compare with the ex- perimental value of K = 2.3. (b) Do you expect a for benzene to depend on temperature? If so, what determines the temperature dependence? (c) Repeat part (a) for chloroform and compare with the experimental value of k= 4.8. (d) Discuss the temperature dependence of K for chloroform.

Answer 1

1. Dielectric constant = Permitivity of material/ permitivity of the vaccum

The permitivity of the vaccume is 8.5 x 10^(-12) F/m and permitivity of benzene = 4 pi x 10.3 x 10^(-30)

Dielectric constant of benzene = 1.53 x 10^(-17)