IUPAC · Global·July each year · rotating host nation
IChOInternational Chemistry Olympiad
The world's most demanding chemistry competition. IChO problems span all branches of chemistry at undergraduate depth — physical, inorganic, organic, analytical — often requiring university-level reasoning in a 5-hour exam. Our simulators cover the most tested theoretical topics.
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Theoretical Exam
5–6 multi-part problems · ~5 hours
Problems span all chemistry domains
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Practical Exam
3–4 lab tasks · ~5 hours
Synthesis, analysis, and identification
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Preparatory Problems
~30 advance problems released ~6 months before
Official host-country prep set
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Selection
4 students per country · via USNCO camp
July each year, rotating host nation
Simulators by IChO Domain
All simulators match topics from IChO preparatory problems and past theoretical exams
Physical Chemistry
Heaviest theoretical weight
Atomic & Quantum Chemistry
Spectroscopy, atomic structure, quantum numbers
Coordination & Inorganic Chemistry
Crystal field theory, d-block, spectroscopy
Organic Chemistry
Reaction mechanisms, stereochemistry, synthesis
Analytical & Equilibrium Chemistry
Titrations, buffers, solubility, Ksp
Nuclear & Radiochemistry
Decay chains, half-life, binding energy
Past Papers & Problem Archive
In Development📐IChO Preparatory Problems
Official prep problem sets from IChO 2001–2025 with detailed model solutions and marking schemes
Q3 2025 📄Theoretical Exam Archive
Full theoretical exam papers and official solutions from past IChO editions (2001–2025)
Q3 2025 🧮IChO-Format Problem Viewer
Multi-part problem interface with sub-question navigation, formula rendering, and solution reveal
Q4 2025 🗂️Preparatory Problem Topic Index
Browse IChO prep problems filtered by topic: thermodynamics, coordination, organic, kinetics, etc.
Q4 2025 Why IChO Prep is Different
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No Curriculum Boundary
IChO problems routinely require first-year university chemistry. Thermodynamic cycles, crystal field theory, advanced spectroscopy, and organometallic reactions are all fair game.
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Heavy Calculation Load
Expect multi-step quantitative problems involving equilibrium constants, electrochemical potentials, partition functions, and Born-Haber cycles in a single question.
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Practical Lab Skills
The practical exam tests synthesis, titration, spectroscopic analysis, and kinetic measurements — all under strict time constraints with real reagents.
Start With the Hardest Topics
No account needed. Every simulator is free.