Question

Chcl3 and ch3cl whose dipole moment is more and why

Answer 1

CH3Cl has larger dipole moment than CH3F because dipole moment is based on the product of distance and charge, and not just charge alone. Fluorine is more electronegative than chlorine, but, the carbon-fluorine bond is also much shorter than the carbon-chlorine bond: 139 pm vs 178 pm. 

Answer 2

Chlorine is more electronegative than Hydrogen so therefore

CH3Cl has more dipole moment

This is due to in CH3Cl chlorine is EWG and it is in one direction and no other group present for cancelling/decreasing its dipole moment