ChemPrep is an optional preparatory OWL course for students prior to starting GenChem.

http://www.chem.umass.edu/chemprep/chemprep.htm

It is optional, and provided as a way for you to be better prepared for the course.  You are still eligible for GenChem, even if you did not chose to take advantage of this opportunity.  ChemPrep does not directly figure into your course grade in Chem 111.