M.Sc

You can get the right answer from some students who are pursuing this course. Generally, Bombay and Kanpur are the best ones since they give their students equal opportunities for placements. M.Sc in Chemistry students sit for placements with B.Tech Chemical. So, you do get a lot of options but competition is stiff. But these vary from IIT to IIT.
So, the student at this position can answer this question better.
I would advise you to do M.Sc from Delhi University as in IITs, there are no specialisation courses.
No IIT offers placement after M.Sc (chemistry) but yes if you are interested in doing Ph.D, you can choose any IIT (Mumbai, Delhi or Madras).

Here, I have mentioned some IITs accepting JAM scores and their eligibility criteria. Form. Sc. Candidate must have Bachelors degree (Geology) and any two subjects among Chemistry, Mathematics, and Biological Science Physics. Also, the candidate must have passed 12th with Math as a mandatory subject. Form. Sc. In IITB Candidate must have passed graduation with both Mathematics and Physics for two years and at least one out of these two for three years. Form. Sc. Biotechnology in IITB and IITR Candidates must have done graduation degree in any of these (Science, Agriculture, Pharmacy, Veterinary, Engineering, and Medicine) branches. Form. Sc. Chemistry in IITG, IITK, IITB, IITD, IITM, and IITR Candidate must have done a graduate degree in chemistry and also candidate must have passed 12thwith mathematics. Form. Sc. Mathematics in IITB, IITD, IITK, and IITM Candidate must have done graduation with Math as a subject for minimum two years or four semesters. Form. Sc. Physics in IITB, IITD, IITG, IITK, IITM and IITR) or Joint. Sc. /Ph.D. (Physics) in IITK Candidate must have done graduation with Physics for minimum two years/ four semesters and also must have done graduation with math for at least one year or two semesters. Form. Sc. Or Ph.D. in Geophysics at IITK Candidate must have done graduation with any two subjects from Physics, Mathematics and Geology minimum 3 years and 6 semesters. Form. Score Ph.D. (Dual Degree) in IITB Candidate must be a graduate in any one of these subjects Physics, Chemistry and Math for minimum two years and four semester.