In 2005, the ACS Examinations Institute released an exam for first-term general chemistry in which items are intentionally paired with one conceptual and one traditional item. A second-term, paired-questions exam was released in 2007. This paper presents an empirical study of student performances on these two exams based on national samples of students who took the exams as part of a general chemistry course sequence. Psychometric data for student performances are presented in terms of classical difficulty and discrimination indexes, as well as item characteristic curves, as are more commonly used in item response theory. Having these data provided for all items on these two exams presents background information that researchers in chemistry education can use in studies in which these exams are part of the assessment paradigm that is used. Finally, because ACS Exams items may not be published, this manuscript presents examples of paired questions that can be used to describe the nature of the exam in subsequent publications that use these exams. (Contains 4 tables and 3 figures.)