Greetings cavalier2012,
A very interesting situation indeed. I am actually traveling the same path. I graduated in 2008 with a B.S. in Chemistry. I always figured I would go back to school for a Masters or PhD in the sciences, but after working in industry for a few years I found that business and management really interested me.
First off, make sure that you really want to get an MBA. Don't just do it because you don't like where you currently are with your Chemistry degree. Pursuing an MBA poses some significant costs. You really have to be sure it will pay off for you. If you're coming from a non-traditional background the pay off is much less certain than for a traditional MBA candidate.
It sounds like you have a vague idea of what you want to do:
"initially, I wanted to go to med school or pharmacy school, but now I've decided that I want to go to business school instead. Helping to manage companies and projects really fascinates me. I want to go into consulting after business school."
So what changed? Did you just sour on the idea of pharmacy school or did you get some management experience that made you want to pursue an MBA. Admissions people are going to be interested in this. If you're not getting real work experience and you're just kinda flip-flopping back and forth between what graduate degree you're gonna get, they will notice and it will probably hurt you.
If you really want to go into project management and/or consulting eventually, I would strongly urge you to try and seek out some type of work experience related to this BEFORE you get an MBA. Make sure that's actually what you want to do.
Further, it's sometimes hard for us science types to really understand that an MBA doesn't change you like a graduate program in Chemistry or Physics will. Grad programs in Science actually put you into the upper tier of the Scientist hierarchy. You learn lots of hard, applicable skills. I think, and someone correct me if I'm wrong, that an MBA is much more about soft skills and networking. If you come out of a program with an MBA degree and no work experience in the field you're trying to get into, I imagine you will find that there are some significant barriers to entry.
I really sympathize with your position because I was where you are about a year ago. I was frustrated with my job and I knew I wanted to go back to school but I didn't know for what. I had soured on grad school for science, and looked at a business degree but didn't know if it was right. What really helped me was seeking out scientists that had gone back for an MBA and were working. In talking to them I really got a feeling for what pursing an MBA would mean and where it would lead me. You should do the same, seek some people out and make sure it's a fit. And I'll stress the work experience thing one more time to drive the point home: try to get business/management experience at your job or find a job with such experience. Doing this will really help clarify whether or not business and management is right for you.
Once you've got some experience under your belt and you know an MBA degree is right for you, the admissions stuff will fall into place. You'll have an admissions story about why an MBA is right for you because you actually had to investigate it. Then just study hard for your GMAT and get a good score and write some really thoughtful essays and you should be good. Your GPA isn't the best but you have a bit of a cushion because you were in the sciences. But you can always take some courses or explain it away. Having the awesome GMAT score would really help you there as well.
I hope I haven't been too repetitive and have helped answer some of your questions. Feel free to ask more if you have any.