International Chemistry Olympiad

IChO 1969

Katowice, Poland · 4 theory problems with complete solutions

  1. Problem 1: Electrolysis of a potassium sulphate solution

    An amount of 20 g of potassium sulphate was dissolved in 150 cm³ of water. The solution was then electrolysed. After electrolysis, the content of potassium sulphate in the solution was 15 % by mass.

    Problem:

    What volumes of hydrogen and oxygen were obtained at a temperature of 20 °C and a pressure of 101 325 Pa?

    Official English text of the problem.

  2. Problem 2: Two potassium-nitrogen-oxygen compounds

    A compound A contains 38.67 % of potassium, 13.85 % of nitrogen, and 47.48 % of oxygen. On heating, it is converted to a compound B containing 45.85 % of potassium, 16.47 % of nitrogen, and 37.66 % of oxygen.

    Problem:

    2.1 What are the stoichiometric formulas of the compounds?

    2.2 Write the corresponding chemical equation.

    Official English text of the problem.

  3. Problem 3: Combustion analysis of a gaseous hydrocarbon

    A 10 cm³ sample of an unknown gaseous hydrocarbon was mixed with 70 cm³ of oxygen and the mixture was set on fire by means of an electric spark. When the reaction was over and water vapours were liquefied, the final volume of gases decreased to 65 cm³. This mixture then reacted with a potassium hydroxide solution and the volume of gases decreased to 45 cm³.

    Problem:

    What is the molecular formula of the unknown hydrocarbon if volumes of gases were measured at standard temperature and pressure (STP) conditions?

    Official English text of the problem.

  4. Problem 4: Products obtainable from calcium carbide and water

    Calcium carbide and water are the basic raw materials in the production of:

    a) ethanol

    b) acetic acid

    c) ethylene and polyethylene

    d) vinyl chloride

    e) benzene

    Problem:

    Give basic chemical equations for each reaction by which the above mentioned compounds can be obtained.

    Official English text of the problem.