How many isomers of dichloroethylene have a zero dipole moment?

There are three isomers of dichloroethylene, they are 1,1 dichloroethylene, cis 1, 2 - dichloroethylene and trans 1, 2 - dichloroethylene. Trans 1, 2 - dichloroethylene is non-polar and has a zero dipole moment while the other two isomers are polar.

There are three dichloroethylen isomers: 1,1, dichloroethylene; 1,2 cis dichloroethylene and 1,2 trans dichloroethyelene.

1,1 dichlorothylene have two Cl - C dipoles on the same side of the molecule and they do not cancel each other, so this isomer has a net dipole moment.

1,2 cis dichloroethylene has two Cl - C dipoles on the same plane so they do not cancel each other, and this isomer also has a net dipole moment.

1,2 trans dichloroethylene has two Cl - C dipoles on different planes and they cancel each other. So this isomer has a zero dipole moment.

The answer is that one isomer of dichloroethylene has a zero dipole moment.