The average pre-reqs include 2 semesters of inorganic chemistry, 2 semesters of organic chemistry, 1 semester of biochemistry, 2 semesters of biology, 2 semesters of physics, 2 semesters of English, 1 semester of statistics, and at least 2 semesters of social sciences. Prepare to take 2-3 of these classes per semester. These classes are difficult but not impossible. Plan on studying 15-20 hours a week for these classes alone, in addition to your elective classes (depending on your major and university, you will take 4 to 5 classes per semester). Some courses will require more, some less. Personally, I found statistics easier (so I only put about 2 hours a week into it), but I found organic chemistry harder (so I put 8-10 hours a week into it).