In ${\mathrm{CH}}_3{\mathrm{CCl}}_3\text{ (I), }{\mathrm{CHCl}}_3\text{ (II) and }{\mathrm{CH}}_3\mathrm{Cl}\text{ (III) }$ ln the normal tetrahedral bond angle is maintained. Also given cos ${70.5}^{\circ }=\frac{1}{3}$Therefore dipole moments of the given compounds are: (given due to -I effect of Cl, the bond moment of H-C bond directed towards the H in ${\mathrm{CHCI}}_3$ )