Question

which of the following molecule(s) is (are) polar? CO2, CH4, CBr4, or CHBr3

Answer 1

The following molecules are symmetrical, so the dipole moments on the bonds cancel out:\[CO_2(linear)\quad CH_4(tetrahedral) \quad CBr_4(tetrahedral)\]
The remaining molecule would have a symmetrical electronic geometry, except that the bonds are not all the same:\[CHBr_3(tetrahedral)\]Since the dipole moments on the bonds do not cancel out, the molecule has a net dipole moment. In other words, it is polar.

Note that water is not linear and it is polar! This is very important. (It has a bent molecular structure, and a version of a tetrahedral electronic structure.)

Answer 2

ok again let me help you understand this. CO2, CH4, CBr4, or CHBr3
first co2 has the same molecule pulling in the same opposite direction so the net dipole cancels
second ch4,cbr4 is nonpolar because you have the 4 molecules canceling the net dipole of eachother, and because ch3br has a strong br pulling in one direction you get a net dipole so there fore its polar