Hey,
Hello all (which appears to be primarily Raza on this particular forum) 
It is weird why CS
Admissions forum is so dull.
It depends on how many schools you are applying to. You have a decent profile and you can get into a top 20 school even a top 10 if you execute your application well. I would not recommend
LOR from a Chemistry professor unless that particular course/project invloved computing then it would be a big plus. If you give GRE subject and getting around 80 percentile, It will strengthen your case for a top 10 school.
Good luck