Question

Among the following, the molecule with the highest dipole moment is 

(a) CH₃Cl 

(b) CH₂Cl₂ 

(c) CHCl₂ 

(d) CCl₄

Answer 1

The correct option (a) CH₃Cl

Explanation:

The dipole moment of a polar molecule depends upon its geometry. A symmetrical molecule is non-polar even though it contain polar bonds. Methane molecule (CH₄) has zero value of dipole moment due to its symmetric structure. We know that the bond dipole moment of C-H bond of C-Cl bond reinforce one another. 

In CHCI₃, the resultant of C-H and C-Cl dipoles oppose the resultant of two C-Cl dipoles while in CH₂Cl₂, the resultant of C-H dipoles adds to resultant of two C-Cl. In case CH₃Cl, the resultant of two C-H dipole adds to the resultant of two C-Cl. In case CH₃CI, the resultant of two C-H dipoles add to the resultant of C- H and C- Cl dipoles. Thus, dipole moment of CH₃CI is highest among the given compounds. The molecule (CCl₄) again becomes symmetrical and dipole moment reduces to zero.