The eligibility for engineering in NIT is as follows candidate must have a pass marks in 12th exam from any recognised educational board. Along with it you must also have good score in JEE MAINS so that your name might come on the merit list of the NITs. Also you won't be given admission just on the basis of 12th marks. And if you plan t o join any other engineering college they will see you PCM marks too and then give you admission.

So since you failed in chemistry I am afraid to say that you chances of getting admissions are very less

Thank you