IChO Problems and Solutions
First held in 1968 in Czechoslovakia, between three countries: four theory tasks, no experiment and no medals. It now runs a theoretical and a practical exam, and every host publishes a preparatory problem booklet months in advance.
2026
Uzbekistan
2025
United Arab Emirates
1 Isocaryophyllene, clovene, and humulene not published 2 Rapamycin - A molecular glue not published 3 Lanterns and the Burj Khalifa not published 4 The life of tennis balls not published 5 Solar-powered multi-stage flash desalination not published 6 Solar energy conversion by CO2 reduction not published 7 Dubai crude oil not published 8 Carbon monoxide: deadly poison or promising therapeutic agent? not published 9 Enzymes and cofactors not published 10 A complex problem not published 11 Exploring the AminOasis not published 12 Rf you ready to spot the answers? not published
2024
Saudi Arabia
1 Ammonia not published 2 Electronic nose not published 3 Tyrosinase not published 4 Potassium not published 5 Unknown not published 6 Penicillin not published 7 Sabic not published 8 Safflower not published 9 Porphyrin complexes not published 10 Indicators not published 11 Titration on a balance not published
2023
Switzerland
1 Molecular Imaging not published 2 Electrochemical CO2 Reduction not published 3 Artificial Photosynthesis not published 4 Fluorinated and Hypervalent Compounds not published 5 Hydrodesulfurization not published 6 Direct Conversion of Methane to Methanol not published 7 Enzyme Kinetics not published 8 Nazarov Reaction not published 9 Electrolysis in Organic Synthesis not published 10 Switzerland - The Country of Pharmaceuticals not published 11 Organic Synthesis: Bleach, a Chameleonic Reagent not published 12 Titration Tango not published 13 Beauty in Simplicity not published
2022
China
1 Rapid and Visual Nucleic Acid Testing for COVID-19 not published 2 Chromium in Ancient and Modern Times not published 3 Capture and Transformation of Carbon Dioxide not published 4 A New Journey for Ancient Sulfur not published 5 Interconversion among Nitrogen Oxides not published 6 Enabling Phosphines not published 7 Organic Molecules in Life not published 8 Amazing Chiral Spiro Catalyst not published 9 Total Synthesis of Capitulactone not published
2021
Japan
1 Hydrogen at a Metal Surface not published 2 Isotope Time Capsule not published 3 Lambert-Beer Law? not published 4 The Redox Chemistry of Zinc not published 5 Mysterious Silicon not published 6 The Solid-State Chemistry of Transition Metals not published 7 Playing with Non-benzenoid Aromaticity not published 8 Dynamic Organic Molecules and Their Chirality not published 9 Likes and Dislikes of Capsule not published
2020
Turkey
1 Two Beauties of Turkey: the Van Cat and the Ankara Cat not published 2 A Tale of a Reactive Intermediate not published 3 (±)-Coerulescine not published 4 Symmetry Does Matter! not published 5 Konya, Carrot, Beta-Carotene, Vitamin-A, Immune System, Vision not published 6 Thermodynamics through an Interstellar Journey not published 7 Phthalocyanines not published 8 Boron Compounds and Hydrogen Storage not published 9 Quantification of Heavy Metal Ions not published
2019
France
1 Infinite well and butadiene not published 2 Hydrogen production by water-splitting not published 3 About silver chloride not published 4 From black powder to the discovery of iodine not published 5 Complexes for the formation of nanomachines not published 6 Characterization of a block-copolymer not published 7 Ring motion in a [2]catenane not published 8 Identification and synthesis of inositols not published 9 Synthesis of levobupivacaine not published 10 Greening the oxidation of nitrobenzaldehyde not published 11 The iron age of wine not published 12 Wine for keeping not published
2018
Slovakia & Czech Republic
1 DNA not published 2 Repatriation of remains in the middle ages not published 3 Emerging electro-mobility not published 4 Column chromatography of radioactive copper not published 5 Bohemian garnet not published 6 Let’s go mushrooming not published 7 Cidofovir not published 8 Caryophyllene not published 9 Haloform reaction with bleach not published 10 A glowing clock reaction not published 11 Mineral water identification not published
2017
Thailand
1 Production of propene using heterogeneous catalysts not published 2 Kinetic isotope effect (KIE) and zero-point vibrational energy (ZPE) not published 3 Thermodynamics of chemical reactions not published 4 Electrochemistry not published 5 Phosphate and silicate in soil not published 6 Iron not published 7 Chemical Structure Puzzles not published 8 Silica Surface not published 9 Into the Unknown not published 10 Total Synthesis of Alkaloids not published 11 Twist & Chirality not published 12 Acid-base indicator and its application for pH measurement not published 13 Calcium iodate not published 14 Elaborating Carbon Framework not published
2016
Georgia
1 Problem 1 not published 2 Problem 2 not published 3 Problem 3 not published 4 Problem 4 not published 5 Problem 5 not published 6 Problem 6 not published 7 Problem 7 not published 8 Problem 8 not published 10 Determination of fluoride and chloride content in mineral water not published 11 Identifying flavors and fragrances not published
2015
Azerbaijan
1 New and well-forgotten old refrigerants not published 2 Coupling of chemical reactions not published 3 Two binding centers – competition or cooperation? not published 4 From one yellow powder to another: A simple inorganic riddle not published 5 Indispensable glucose not published 6 Bread is the stuff of life not published 7 Not by bread alone not published 8 Oil for Life and Life after Oil not published 9 Tuning bromination selectivity by catalysis not published 10 Analysis of the solution of a chromium – vanadium alloy not published 11 Kinetic determination of Diclofenac (DCF) not published
