Understand the exam format

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Local Exams Format

Multiple Choice

110 min | 60 multiple-choice questions
Covers broad chemistry topics

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National Exams Format

Part I: Problem Solving

90 min | 60 multiple-choice questions
Covers broad chemistry topics

Part II: Problem Solving

105 min | 8 written questions
Covers chemical theories and models

Part III: Lab Practical

90 min | 2 laboratory practicals
Involves problem solving in the laboratory

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Multiple Choice Topics

Multiple choice USNCO (both local and national) exams cover the following topics:

 1 – 6  Stoichiometry/Solutions
 7 – 12  Descriptive/Laboratory
 13 – 18  States of Matter
 19 – 24  Thermodynamics
 25 – 30  Kinetics
 31 – 36  Equilibrium
 37 – 42  Oxidation - Reduction
 43 – 48  Atomic Structure/Periodicity
 49 – 54  Bonding/Molecular Structure
 55 – 60  Organic/Biochemistry

Number of Nominees

More than 1,000 students sit for the three-part National Exam each April. Coordinators nominate students for the National Exam based on the results of the Local Competitions. Each Local Section can nominate only a certain number of students determined by the number of its ACS members. No more than two students from any given school can compete in the National Exam.

See the allowed numbers of nominees below or downoad a PDF of the allotment of nominees by ACS Local Section.

ACS Members USNCO Nominees
1–1000 10
1001-1350 11
1351-1700 12
1701-2050 13
2051-2400 14
2401-2750 15
2751-3100 16
3101-3450 17
3451-3800 18
3801-4150 19
ACS Members USNCO Nominees
4151-4500 20
4501-4850 21
4851-5200 22
5201-5550 23
5551-5900 24
5901-6250 25
6251-6600 26
6601-6950 27
6951-7300 28
7301-7650 29
Students during the Chemistry Olympiad laboratory work
Students during the Chemistry Olympiad laboratory work


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.


The 20 top-scoring students are invited to attend a study camp to compete for a spot in the U.S. team. Based on the score of their overall performance, some students are recognized with High Honors and Honors and receive a certificate from the USNCO national office. Approximately 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.

Learn about the exam format and how to prepare for exams.