Hi Soumya !
You can go for either one of them depending on your interest as chemical engineering & computer science both are best streams but personally i would suggest you to go for computer science with BITs Pilani as C.S comes before Chemical in order of preference.
Please feel free to post as many doubts on our disucssion forum as you can. If you find any question difficult to understand - post it here and we will get you the answer and detailed solution very quickly. We are all IITians and here to help you in your IIT JEE preparation.
All the best.
Manisha Sharma
