Chemical Engineering or Architecture??  

If you think you have an eye for arts and architecture then go.. Architecture is not solely for having the ability to draw. You have to be creative in masses not just blocks.

I'm an Architecture graduate, and I say its fun to study architecture. You become aware of history and culture. You'll understand why layout is planned. And you'll understand how such structure stand. Its a combination of science and art.

What I also like in this career, once you become licensed Architect you can be part of the history. Since the building you design stand a long long long time...

Well, go to this link in the videos section you will find videos that will help you.
This is an architectural site.
So, it will help you better than any comments as architecture is to feel, see and listen and not to read.
So see the videos that will clear all your doubts as they cleared mine.
I am happy I am really able to help you as there was no one to help me when I needed help.
Also, take don't take admission in NIT, patna. You can take admission in any other NIT. Put SPA as your first choice.

Architecture is a good option if you are passionate about it. Architecture is both an art and science. If you enjoy designing, computations, history, buildings, and theories their is a good chance you will enjoy this profession.

i dont know about the Indian school system, but as far i know,

i think Chemical Engineering is more tecnical that Architecture. In Architecture you have to think about a project (house, office) and drawing it, and the Chemical Engineering you have to discover new substances or fabric new ones to a lot of things.
My guess is, go to the course that you think you are more capable, not the one who give more points or something like that, because when you reach to the job market in the real society, the type of your course and your skills are more important than the points you have taking during the course.

good luck to you, aromalram !