Cuban National Chemistry Contest 2017
This contribution compiles the problems, solutions and results of the Cuban chemistry olympiad for high school students celebrated nationwide in 2017. The Cuban National Chemistry Contest (CNQ, Concurso Nacional de Química, official name in Spanish) is a yearly competition intended to stimulate high school students the study chemical sciences during their bachelor's. It is sponsored by the Cuban Ministry of Education (MINED, official acronym in Spanish). Tenth-, eleventh- and twelfth-graders (15-17 years old, on average) are welcome to participate. This event is preceded by the Municipal Contest at each high school and the Provincial Contest in every province of Cuba. Winners of the latter are invited to participate in the national event. This Cuban chemistry olympiad takes place at the Vocational High School for Exact Sciences (IPVCE, official acronym in Spanish) in every province. It is organized as a two-day event in February or March every year. During the competition, the students try to solve two sets of theoretical or theoretical-practical problems elaborated by previous olympics and mentors. The qualification of the exams is performed in Havana by a tribunal integrated by selected teachers from all over the country. The highest scores are priced with gold, silver and bronze medals. Top winners can choose any career in science and the university they like the most to continue their studies with no need for additional requisites. In addition, they are part of the national pre-selection and are invited to Havana for a short training period. After a final selection round, the national team for the international chemistry olympiads is formed. As a particularity of the 2017 national contest, the Faculty of Chemistry of the University of Havana designed the problems. In the current edition, there were two theoretical problem sets. The first-day exam was intended for all grades (common problem set) and had four problems. Problem 1 had a multiple-choice format and was about general chemical knowledge. Problem 2 analyzed the kinetic data of a nucleophilic bimolecular substitution. In Problem 3, the student had to find the composition of an inorganic mixture through stoichiometry calculations. The second-day exam consisted of an individual problem set for each grade. Tenth-graders explored the combustion of ribose in Problem 4, the reactions of sodium compounds in Problem 5, the Born-Haber cycle of sodium chloride in Problem 6 and identified a non-metal and its oxygenated compounds in Problem 7. Eleventh-graders found the hydrate form of sodium sulfate in Problem 8, calculated the acidity of rain in Problem 9 and explored chlorine production in Problem 10. Twelve-graders derivatized carboxylic acids in Problem 11, found the stereochemistry of epoxide and diol formation in Problem 12 and calculated the solubility product of electrolytes in Problem 13. Herein, the problem sets are provided in the official Spanish version and English translation.