Hello,

You have not mentioned the state it is confusing as there is St.Xavier's college in Kolkata as well as in Mumbai.But the admission in B.Sc Chemistry (hons) is based on merit in 10+2 with atleast 60%.There is no separate exam conducted.You need to fill the online application form and the cut off list will be prepared after the declaration of 10+2 results.If you have scored minimum cut off marks then you need to go for certificate verification and you will be informed about the allotment of seat.

You can click the link below for other detailed information

St. Xavier's  College, Kolkata (https://www.sxccal.edu/admissions/sxcadmission2019/ug9102/default.htm)

St.Xavier's College, Mumbai (http://xaviers.edu/main/index.php/admissions-and-courses)