Hi Aparna,
M.Sc Chemistry comprises of 4 semesters that means it is a two years course. Through M.Sc Chemistry you may specialize in a number of fields like Polymer Sciences, Analytical Chemistry, Bio Analytical Chemistry, Material Sciences,  etc
Eligibility : Candidate must possess a B.Sc degree with Chemistry as a subject and most of the college also have a 50% minimum aggregate condition also.
Most of the colleges make admissions to their M.Sc programs with the score of JAM.
If you want to know about any particular college admission then you may let me know.
Hope it helps :)