Question

due to which chemical reaction is taj mahal getting yellow?

Answer 1

actually the marble of taj mahal contains calcium carbonate. And some harmful acids like sulphuric acid present in rain is responsible for corroding it.

Answer 2

it is due to many industries surrounded to it, especially Mathura oil refinery which is releasing many toxic gases like sulphur....and other reason is due to acid rain which is making it in yellow colour(fading)......

hope it helps you.... :)