If your school has an option to take electives for a pass or fail grade then a pass will likely just be ignored. It says nothing about how you did in the course. You could have gotten a 65 or a 99 and the admissions committee would not know. They will assume you took the course for a Pass because you want to explore something new and exciting or had a lot on your plate that semester. Nobody cares.

The one exception is your premedical requirements. You should not be taking these courses for Pass/Fail grades. Medical schools want to see how you scored in this course. Opting to take organic chemistry for a pass grade will simply tell the committee you were afraid you would get a bad grade and therefore took this notoriously difficult course pass/fail.