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Decoding of Chemistry Olympiad

Decoding of Chemistry OlympiadDecoding of Chemistry OlympiadDecoding of Chemistry Olympiad

Decoding of Chemistry Olympiad

Decoding of Chemistry OlympiadDecoding of Chemistry OlympiadDecoding of Chemistry Olympiad
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    • Home
    • About
    • USNCO
      • General Overview
      • FAQs
      • Learning Objectives
      • DCC
      • Annotated Solutions
      • Misconception
      • Laboratory
      • Study Camp
    • Classes
      • Introduction
      • Registration
      • Placement
      • Testimony
      • National Preps
      • Open Classes
      • Lecture Notes
    • Resources
      • Textbooks
      • IChO
      • CChO
      • Mendeleev
      • VChO
      • WUCT&BCT
      • Other Sites
    • Consultation
      • Newsletters
      • Email
      • Discord
      • WeChat 微信
  • Home
  • About
  • USNCO
    • General Overview
    • FAQs
    • Learning Objectives
    • DCC
    • Annotated Solutions
    • Misconception
    • Laboratory
    • Study Camp
  • Classes
    • Introduction
    • Registration
    • Placement
    • Testimony
    • National Preps
    • Open Classes
    • Lecture Notes
  • Resources
    • Textbooks
    • IChO
    • CChO
    • Mendeleev
    • VChO
    • WUCT&BCT
    • Other Sites
  • Consultation
    • Newsletters
    • Email
    • Discord
    • WeChat 微信
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)

Check our work here

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

IChO Problems by Year (1968-2013) - Downloads

VolumI(1to20)IChO (pdf)

Download

VolumII(21to40)IChO (pdf)

Download

VolumIII(41to45)IChO (pdf)

Download

IChO Problems by Subject (1972-2017) - Downloads

Analytical_Chemistry (pdf)

Download

Inorganic_Chemistry (pdf)

Download

Organic_Chemistry (pdf)

Download

Physical_Chemistry (pdf)

Download

Practical_Problems (pdf)

Download

Copyright © 2018-2025 Decoding of Chemistry Olympiad - All Rights Reserved.

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Interested in Chemistry Olympiad Classes for 25–26?

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  1. Self-Study + Diagnostic
    Study Honors or AP Chemistry on your own, then take Dr. Chen’s diagnostic tests to determine fall placement. Recommended textbooks
  2. Summer Class with Dr. Chen
    Take an intensive AP Chemistry+ or Organic Chemistry Class this summer with Dr. Chen to prepare for Level 2, 3, or 4 Olympiad training in the fall.
  3. Start Now – Self-Paced
    Prefer to begin right away? Purchase recordings and materials for Level 2, 3, or 4 from 2024-25 and start learning at your own pace!

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