^Of course MIT's OCW isn't designed for AP exams (why would it be anyway?). Also, it is definitely possible to get a 5 by just watching OCW lectures...might be a little harder, but it's possible.
Thing is, 5.111 is a little more advanced than AP Chem (taking it this semester btw), so there are several topics that don't appear on the AP test. There are a few (but not many) topics that are in AP Chem but not in 5.111. You can definitely watch the 5.111 videos, but you may want to supplement with an AP Chemistry workbook.