Greater the value of electronegativity, higher the dipole moment. So, CHF3 is expected to have greater dipole moment. But, due to extreme smaller size of fluorine, the dipole moment of CHCl3 outerweighs that of CHF3. And for the others, it’s all about electronegativity.
In the second order:
Even though F is more electronegative, CH3Cl has greater dipole moment because the bond length in this case is far longer than that in the case of CH3F since F is highly electronegative and it attracts the electron pair very strongly. Dipole moment is not just about charge, it is the product of charge and the bond length.
Electronegativity is the determining factor for the others.
Ch3f Dipole Moment
The order of electronegativity for halogens is F > Cl > Br > I……….therefore order of dipole moment in given compounds will be …….CHF3 > CHCl3 > CHBr3 > CHI3……and ……..CH3F > CH3Cl > CH3Br > CH3I……….
As the polar nature of CH-X bond is expected to increase with increase in the electronegativity difference between carbon and halogen atom. & we know electronegativites of the halogens are: F 4.0 Cl 3.5 Br 2.8 I 2.5 Hence the order of bond dipole moment here is CHF3> CHCl3>CHBr3>CHI3 Hope you have got it..(: