Which one of the following has the highest dipole moment?
(i) `CH_(2)Cl_(2) , (ii) CHCl_(3) , (iii) C Cl_(4)`

Explanation

The three dimensional structures of the trhee compounds along with the direction of dipol moment in each of their bonds are given below:

`C Cl_(4)` being symmetrical has zero dipole moment. In `CHCl_(3)`, the resultant of two C-Cl dipoles is opposed by the resultant of C-H and C-Cl bonds. since the latter resultant is expected to be smaller than the former, therefore, `CHCl_(3)` has a finite dipole (1.03D) moment.
In `CH_(2)Cl_(2)`, the resultant of two C-Cl dipolemoments is reinforced by resultant of two C-H dipoles, therefore, `CH_(3)Cl_(2)(1.62D)` has a dipole moment higher than that of `CHCl_(3)`. thus, `CH_(2)Cl_(2)` has the highest dipole moment.