Hey Gayathri.

For admission in the course of MSc Chemistry through IIT JAM the eligibility criteria laid down for admission, requires you to study Chemistry for three years/six semesters in your Bachelors degree amd also study Mathematics as a subject in Class 12th. Hence you need to have studied Chemistry in your Class 12th. You can use the link below to see the eligibility criteria for various courses under IIT JAM.

https://www.google.com/amp/s/university.careers360.com/articles/jam-eligibility-criteria/amp

Best of luck