Grad school isn't a decision you should take lightly. You can think you want to go, apply, get accepted, and defer a year--I wish I had done that, honestly. You can go anywhere you want if you have the right combination of test scores, GPA and recommendations. Honestly, I think the recommendations go the farthest. If you know a certain school you want to go to, find a professor you've had who went there or did a post-doc there--it will help. The first couple of years of any PhD program worth its salt will be utter misery. Too much work. They want to weed people out by attrition. Then it gets better with your research, and it can be a lot of fun if you like what you're doing. I got into Berkeley with a GPA that's lower than that, so you'll be fine unless your test scores are horrible. Competition varies by school. If you go for one of the top 10 in chemistry, i.e., Berkeley, Harvard, U of Illinois-Urbana-Champaign, U of Wisconsin-Madison, CalTech, Stanford, Princeton, MIT, etc., competition will be more selective. If you want to go to a state school, you'll get in for sure. Whatever you do, don't get your PhD in chemistry at the same place you did your undergrad--it looks bad on your resume for whatever reason.
My biggest piece of advice is to take a look at the area you want to live in. Make sure the town and the people in the department are nice, because they will be your support network when you're in grad school. I should have considered that more before I came out here. I hate the town of Berkeley, and it was exceedingly difficult my first two years out here. The only thing that saved me was the comradarie of the grad students here. This town (and the state, really) is the worst place I could have chosen to live, but the school is excellent and the students are great, so it will hopefully be worth it in the long run. I would also choose a school that has a good Physical Chemistry program (check out Chemical and Engineering News at your library for the yearly report on grad schools--I think it's in the spring; we might even have a thread about it at the forums here), choose a professor and a project you're interested in, and make sure you like this person well enough to work for them for 5 years. Your advisor will make a tremendous difference in your life in grad school.