It is difficult to predict marks for Jee advanced because the paper pattern and total marks in not consistent. It changes every year.

In terms of rank in 2017,  the closing rank in IIT BHU for Chemical Engineering is 5900 for general category.

For your information the cutoff varies for all branches and reserved categories.

For OBC the last rank is 2318

For SC the last rank is 1345

For ST the last rank is 756

Good Luck.