Has ccl4 a dipole moment

Which of the following molecules has a dipole moment? CCl4, H2S, CO2, BCl3, Cl2

Just because of the symmetry we know that # H_2S # is the only one of these molecules that has a dipole moment.

In the case of # Cl_2 # If the 2 atoms are identical, no polarization of the bond is possible and the dipole moment is zero.

In any other case except # H_2S #, the polarization of the charge associated with each bond is exactly canceled by the other bonds, resulting in no net dipole moment.

For # CO_2 # every CO bond is polarized (with oxygen taking a partial negative charge and carbon taking a positive charge). However, # CO_2 # is a linear molecule, so the two CO bonds are polarized in the same and opposite directions and exactly equalize each other. Therefore, # CO_2 # has no dipole moment.

For # H_2S # the bonds are both polarized, but # H_2S # is a bent molecule, not linear, so the polarizations do not cancel, and # H_2S # has a net dipole moment.

For # BCl_3 # the geometry is an equilateral triangle of Cl atoms with the boron atom in the center of the triangle. The polarization of the 3 B-Cl bonds is canceled out exactly # BCl_3 # has no dipole moment.

Similarly, the 4-C-Cl bonds in CCl4 are oriented to point to the vertices of a regular tetrahedron, and they cancel each other out exactly so that CCl4 has no dipole moment.