It really depends on what your individual preferences are. In chem the labs will loosely follow lecture, so it really wouldn't put you at a disadvantage to take the lab immediately afterwards.
I've done both, and they are each nice for different reasons and each has their drawbacks. I liked taking lab immediately right after lecture as I was able to focus on the subject all at one time instead of breaking it up throughout the week -- I also felt like I had more free time this way even though it's kind of psychological.
On the other hand, assuming you don't have separate exam dates from lecture, there will be times when you'll have lab immediately right after a test. This puts extra pressure on you because you then have to study for the test AND get your pre-lab work done, while if you had lab at a different time you wouldn't have as much to prepare for in the same amount of time.
So if you're not sure, I would generally recommend taking lab on a different day from lecture if you're just starting college and you're not sure what works well for you yet.