Hello
Working on the IChO 2025 PP together with Dr. Chen?
Dr. Chen and his students are working on the IChO 2025 Preparatory Problems, if you are interested, please check out our unofficial solution linked below and let us know if you have any questions (chen@dcho.us)
International Chemistry Olympiad
IChO "Official"
Past Problem by Subjects
IChO "Official"
everything about IChO you need to know, including the history, the results, etc.
Past Problems
Past Problem by Subjects
IChO "Official"
The collection of past problems from 1968-2013 is available in three parts
Past Problem by Subjects
Past Problem by Subjects
Past Problem by Subjects
from the Italian national chemistry olympiad website
IChO 2025, United Arab Emirates
IChO 2025, United Arab Emirates
IChO 2025, United Arab Emirates
- prep problems, solution (in progress, by Dr. Chen and his students)
- theoretical problems, solution
- difficulty index:
- fun index:
IChO 2024, Saudi Arabia
IChO 2025, United Arab Emirates
IChO 2025, United Arab Emirates
- prep problems, solution (unofficial)
- theoretical problems, solution
- difficulty index:
- fun index:
IChO 2023, Switzerland
IChO 2022, China (virtual)
IChO 2022, China (virtual)
- prep problems, solution
- theoretical problems, solution
- difficulty index: 3/5
- fun index: 4/5
IChO 2022, China (virtual)
IChO 2022, China (virtual)
IChO 2022, China (virtual)
- prep problems, solution
- theoretical problems, solution
- difficulty index: 3/5
- fun index: 3/5
IChO 2021, Japan (virtual)
IChO 2020, Turkey (virtual)
IChO 2020, Turkey (virtual)
- prep problems, solution
- theoretical problems, solution
- difficulty index: 4/5
- fun index: 5/5
IChO 2020, Turkey (virtual)
IChO 2020, Turkey (virtual)
IChO 2020, Turkey (virtual)
- prep problems, solution
- theoretical problems, solution
- difficulty index: 3/5
- fun index: 4/5
IChO 2019, France
IChO 2020, Turkey (virtual)
IChO 2018, Czech & Slovakia
- prep problems, solution
- theoretical problems, solution
- difficulty index: 3/5
- fun index: 5/5
IChO 2018, Czech & Slovakia
IChO 2018, Czech & Slovakia
IChO 2018, Czech & Slovakia
- prep problems, solution
- theoretical problems, solution
- difficulty index: 3/5
- fun index: 5/5
IChO 2017, Thailand
IChO 2018, Czech & Slovakia
IChO 2017, Thailand
- prep problems, solution
- theoretical problems, solution
- difficulty index: 3/5
- fun index: 3/5
- website was down!
IChO 2016, Georgia
IChO 2018, Czech & Slovakia
IChO 2017, Thailand
- prep problems, solution
- theoretical problems, solution
- difficulty index: 5/5
- fun index: 4/5
- website not fully working!
IChO 2015, Azerbaijan
IChO 2015, Azerbaijan
IChO 2015, Azerbaijan
- prep problems, solution
- theoretical problems, solution
- difficulty index: 5/5
- fun index: 4/5
IChO 2014, Vietnam
IChO 2015, Azerbaijan
IChO 2015, Azerbaijan
- prep problems, solution
- theoretical problems, solution
- difficulty index: 3/5
- fun index: 3/5
- website not working!
IChO 2013, Russia
IChO 2015, Azerbaijan
IChO 2012, United States
- prep problems, solution
- theoretical problems, solution
- difficulty index: 5/5
- fun index: 4/5
- website not working!
IChO 2012, United States
IChO 2012, United States
IChO 2012, United States
- prep problems, solution
- theoretical problems, solution
- difficulty index: 3/5
- fun index: 4/5
IChO 2011, Turkey
IChO 2012, United States
IChO 2011, Turkey
- prep problems, solution
- theoretical problems, solution
- difficulty index: 3/5
- fun index: 4/5
- website was gone!
IChO 2010, Japan
IChO 2012, United States
IChO 2011, Turkey
- prep problems, solution
- theoretical problems, solution
- difficulty index: 3/5
- fun index: 4/5
Preparing for USNCO 2026?
Choose the path that fits you best:
1. Take Live Lessons with Dr. Chen – weekly class from late Aug to early Apr
- Taking AP Chemistry in the fall --> Level 2
- Completed AP Chemistry --> Level 3
- Aiming for Winning National --> Level 4
- Not sure which Level? --> take the diagnostic test
2. Prefer to begin right away? – Self-paced
Purchase recordings and class materials for Level 2, 3, or 4 and Summer Organic Chemistry in 2024-25 and start learning at your own pace!