^ Apparently as of this fall they’re redoing requirements for CHE 2A, so not everyone will have to take the placement exam.
Source: http://chemistry.ucdavis.edu/undergraduate/chemistry_placement_exam.html
Still, it wouldn’t hurt to take it. You have a couple more days, so I’d recommend getting it out of the way if you’re going to do it so you don’t need to worry about it later.
And frankly, many/most people go into orientation clueless. They’ll get you up to speed.