It gives me immense pleasure to express my sincere thanks to the teachers as well as the student-community for widely accepting the fourth edition of this book. Their suggestions and comments have prompted me to bring out this revised edition. The fifth edition has been revised and updated keeping in view the latest requirements of the course/syllabi prescribed by Kurukshetra University, Kurukshetra w.e.f 2015–16 and by way of including the previous years question papers. On the suggestions of teachers, some corrections and alterations have also been incorporated. My sincere thanks are due to Dr. A.Pal professor of chemistry, Kurukshetra University, Kurukshetra, Dr. Sanjeev Arora, Associate professor of chemistry, Kurukshetra university, Kurukshetra, Dr. V.K Syal, former professor of chemistry, Himachal Pardesh University, Shimla, now professor of chemistry, KIIT college of Engineering Maruti Kung, Gurgaon, Dr. K.S. Sinha, former professor of chemistry, Magadh University, Bodh-Gaya (Bihar), Dr. Ram Kishore Manchiryal, Deptt. of civil engineering (Middle east college, Muscat, Oman), Dr. Arvind Devangan, professor of Civil Engg., Haryana College of technology and Management, Kaithal and Sh. Amit Kumar Ambasta, a Research Scholar, deptt. of physics, ISM (now known as IIT) Dhanbad for their valuable suggestions for the improvement of the book. I am also very much thankful to my collegeous Prof. (Dr.) Amit Vashistha and Dr. Parveen Kumar Gupta, deptt. of chemistry, Haryana College of Technology and Management, Kaithal for helpful discussion.