Select which one is polar

Question

I am having trouble finding out which one of these three are or is polar.

 

Select the chlorofluorocarbon(s) (CFCs) that is/are polar.

 

1. Freon-C318 (C4F8, cyclic structure)

 

2. Freon-122 (C2HCL3F2)

 

3. Freon-111 (C2Cl5F)

Answer 1

You need to draw the structures for each molecule and see if the halogens are "pulling" electrons in opposite directions (thus cancelling each other's effects) or there's any asymmetric pull, which would cause the molecule to be polar.