# United States National Chemistry Olympiad

The United States National Chemistry Olympiad (or USNCO) is a contest held by the American Chemical Society (ACS) used to select the four-student team that represents the United States at the International Chemistry Olympiad (IChO).
Each local ACS section selects 10 students (or more for larger ACS sections) to take the USNCO National Exam. To qualify for the national exam, students must first take the local exam. Approximately 10,000 U.S. students sit for the local exam each year. More than 1000 students qualify to take the National Exam annually.

## Exam format

The National Exam consists of three parts.

### Multiple choice

The first part consists of 60 multiple-choice questions. Each question has four answer choices, A, B, C, and D. The questions are loosely grouped into 10 sets of 6 items; each set corresponds to a different chemistry topic. Typically, the topics are, in order, descriptive chemistry/laboratory techniques, stoichiometry, gases/liquids/solids, thermodynamics, kinetics, equilibrium, electrochemistry, electronic structure/periodic trends, bonding theories, and organic chemistry. There is no penalty for guessing; a student's score is equal to the number of questions answered correctly. One and a half hours (90 minutes) are allotted for this first part.

### Free response

The second part contains 8 free response questions. Complete written explanations and calculations are required for full credit on a question, and partial credit is awarded. More thorough knowledge of basic theories is required, and often there are questions on less-emphasized portions of normal high school chemistry curricula, such as organic chemistry and coordination chemistry. One hour and 45 minutes (105 minutes) are allowed for this section. The topics of each question in the recent part II’s of USNCO usually follows the following format:
Q1: Stoichiometry
Q2: Equilibrium
Q3. Assorted (typically either thermodynamics, electrochemistry, or kinetics)
Q4. Assorted (typically either thermodynamics, electrochemistry, or kinetics)
Q5. Prediction of chemical reaction products. Includes acid-base reactions as well as redox reactions. Part F is usually on radioisotope decay.
Q6. Assorted (could be any topic that is not anywhere else)
Q7. Bonding
Q8. Organic Chemistry

### Lab practical

Beginning in 1994, the lab practical was added to the National Exam. It contains two tasks to be performed by each student with only the specified materials, and students are expected to describe their procedures and organize their findings. Past tasks have included chromatography, titration and qualitative analysis, and 90 minutes are allotted to complete the two experiments.

## USNCO Study Camp and other recognition

The top 20 scorers on the USNCO National Exam are invited to participate in the two-week USNCO Study Camp at the University of Maryland, College Park in College Park, Maryland. At the camp, the students are tested (both free response and lab testing), and the top four students are selected to comprise the U.S. IChO team. Two alternates are also selected, although no alternate has ever actually been called up for duty.
In addition, the top 50 students are recognized as achieving "High Honors" or "t50", and the next 100 students earn the "Honors" or "t150" designation.

## Preparation for USNCO
### Local Exam:

To perform well in the local exams, students are expected to have a decent understanding on common AP Chemistry topics, such as equilibrium, stoichiometry, or electrochemistry. A superficial understanding of descriptive chemistry (e.g. common ion colors or laboratory practices) and organic chemistry is also extremely useful.

### National Exam:

Part I: This part of the exam consists of 60, shorter, multiple choice questions. However, deeper understanding of AP Chemistry material and a general understanding of organic chemistry is critical to performing well on this part of the national level exam. Basic material science knowledge, such as unit cells or density calculations may also be asked. Occasionally, simple biology questions may also be asked in the organic chemistry section (Q55 - Q60).
Part II: This part of the exam consists of 8 questions that are more challenging than part I. Extensive understandings of chemistry topics are required to perform well on this part. Students should focus on any weak areas, especially with conceptuals.
Part III: This part of the exam consists of a lab block, where two objectives are presented to students to investigate, by designing a lab and performing it. Students may sharpen their lab skills prior by performing labs with their class.

### Test-taking Tips:

- Oftentimes, students finish the 60 questions on the Local Exam with time to spare. Thus, it is wise to skip over any challenging questions and return to them later on the local exam.
- There is no penalty to incorrect answers, so it is to the students' advantage to answer every question.
- On Part II of the national-level exam, answers from a subsection of a question may or may not be information required in the next subsection of a question. I.e. even if one may have skipped part a of the question, they may be able to answer part c of the same question.
- Lab investigations are oftentimes common AP chemistry experiments, such as acid-base titrations. It is thus possible to answer part III with minimal lab preparation.

### General Preparation :

The American Chemical Society provides problems and some solutions from past years at both local and national levels for all portions of the tests. It may be found here.
USNCO quizzes, a fan-created website not affiliated with the American Chemical Society provides questions from part I one at a time. Problems are grouped into specific categories. Due to the nature of this format, it allows for a less time-consuming way to practice alternative to the longer 60 question test.
Online forums such as the Chemistry Olympiads Discord community commonly have solutions to USNCO questions that the ACS doesn't provide a solution for.
Valuable equations such as integrated rate laws are not included on the given reference sheet. In fact, only three equations are provided! It is up to the student to memorize the remaining equations, such as Raoult's law or the Ideal gas law. However, many constants such as Faraday constant are provided.

## Scope of the test as compared to the IChO

The purpose of the USNCO is to stimulate all young people to achieve excellence in chemistry. Therefore, the focus of the exam is not necessarily to select the top twenty students, and instead to present a wide selection of basic questions. Therefore, the scope of the USNCO is different than the scope of what would be expected at the training camp or IChO.