Richard Langley holds a Ph.D. in inorganic chemistry from the University of Nebraska-Lincoln. He has taught chemistry at the university level for nearly 40 years. He is the author of 500 Physical Chemistry Questions and coauthor of 1,001 Practice Problems for Chemistry for Dummies, Chemistry for the Utterly Confused, Biochemistry for Dummies, 5 Steps to a 5 AP Chemistry, and Must Know High School Chemistry, among other works. He has been a grader for the AP Chemistry Exam for many years.