National Chemistry Olympiad Exam

More than 1,000 students sit for the 3-part National Exam each April. Coordinators nominate students for the National Exam based on the results of the Local Competitions. No more than two students from any given school can compete in the National Exam. The 20 top-scoring students are invited to attend a study camp to compete for a spot in the U.S. team.

National Exams are often hosted by ACS Local Sections at local universities and colleges. ACS Local Sections recognize USNCO National Exam nominees with certificates, monetary prizes, plaques, or other gifts. Many Local Sections honor the students, their teachers, parents and volunteers at award banquets, luncheons and dinners.

National Examination

The three-part, 4 hour and 45 minutes exam consists of the following (may be administered in any order):

Students during the Chemistry Olympiad laboratory exam
Part I Part II Part III
  • Multiple Choice
  • 90-minutes
  • 60 multiple choice questions
  • Covers broad chemistry topics
  • Problem Solving
  • 105 minutes
  • 8 written questions
  • Covers chemical theories and models
  • Lab Practical
  • 90 minutes
  • 2 laboratory practicals
  • Involves problem solving in the laboratory

How to Prepare

Students can use the past National Exams as guidance to help them study for the tests. Past IChO Exams can also be used in preparation, as each year's study camp curriculum is based on preparatory problems posted by the host country.


ACS calculates the average number of correctly answered questions by topic area. Based on this average, each student's score in a particular topic is compared to the overall average and rated as: Below Average, Average, Above Average, or Outstanding Performance.

Only student scores for Part I (multiple-choice) are sent to the Local Section coordinators to be distributed to students.


Based on the score of their overall performance, the top 150 students are recognized as high Honors and Honors and receive a certificate from the USNCO national office. The top 50 students are recognized as High Honors and the next 100 as Honors. The list of High Honor and Honor students is published on the USNCO website.