Dr.R K Choudhary, the author of this book, received his B.Sc. Hons & M.Sc. degrees in Chemistry from Bhagalpur University, Bhagalpur, and PhD degree in Science from L N Mithila University, Darbhanga. He has teaching experience of over 26 years in Universities and 24 years in nationally acclaimed JEE (Advanced) coaching institutes. He has successfully guided some research scholars at the doctoral level and has published research papers in Chemical journals of repute. His contributions in all these fields have made him a familiar name in the country. This book is a direct manifestation of his long experiences in teaching and research. The author is pleased to wish all the best to all such students for their bright future.