it won't be a problem if you can handle that many hours of lab. If you're also taking physics lab (or any other lab), I'd try to separate the ochem labs into different quarters if possible. I just think you might be putting too much into lab hours and it might affect how you do in classes cuz of the time you're spending in lab and not studying. But if that's not a prob, it should be ok cuz you don't really need the first lab to do well in the second lab -- the techniques are easy to pick up.