Hello Aspirant, the cutoffs change from year to year, the qualifying marks for chemistry in IIT-JAM is  27 marks. The closing rank would be around 320. You can check the cutoffs and have a clarity whether you are eligible or not at the official website http://jam.iitkgp.ac.in/jam2019/jam2019/doc/JAM-2019-Round1_Cutoff.pdf .

The initial round and final round cutoff's are almost similar.

Hope this helps.

Thank you.