Question

Gaseous mixtures __________. can only contain isolated atoms can only contain molecules are all heterogeneous are all homogeneous must contain both isolated atoms and molecules

Answer 1

Hello there,
Gaseous mixtures may or may not contain only molecules or only atoms. They need not contain either, isolated atoms and isolated molecules.
For example:
1) He + Ne no molecules
(sorry only 1 could come up to my mind)
Thus the answer is homogeneous 

Hope this helps :))

~Top

Answer 2

All are homogeneous


Good luck! (: