Which of the following are chiral? (Consider configuration only; rings are treated as planar and time-averaged.)

Cis isomers of 1,2- and 1,3-disubstituted rings with identical substituents have a mirror plane through the ring (meso, achiral). The trans isomers have no mirror plane or inversion centre, so trans-1,2-dibromocyclopentane and trans-1,3-dichlorocyclopentane are each chiral and exist as enantiomeric pairs.