You will be asked reasons for previous B-1 application and now an F-1. Tell them you wanted to visit the US before deciding on a school but since B-1 visa got rejected, you are now directly going for an F-1 and hoping for the best. There is no need to change consulates, and be truthful on your DS form - always.
Dr. Sandeep Shankar, Colorado Heights University, Denver, CO 80223, USA. www.chu.edu; Email: firstname.lastname@example.org