2018 Competition


2018 Individual Round Solution

Corrections

  • In part (c) of question 1, "that acetic solution" refers to the 0.300M solution in part (b).
  • In part (e) of question 5, given an appropriate explanation, both "endothermic" and "exothermic" are valid answers. However, since the question specifically states an answer must be based on the information in the question(see "Given this information"), only a complete answer that argues that the reaction is endothermic can receive full credit. A complete answer that argues that the reaction is exothermic can only receive up to 1 point of credit. This point of credit is given because, in the lab setting, the reaction is initially endothermic but becomes exothermic over time.
  • In part (b) of question 3, given a complete explanation, an argument that Al and/or Mn protect Fe and slow corrosion is awarded 2 points. A complete argument that Cu speeds up corrosion and Al slows corrosion is awarded 3 points. An argument that the metals increase the voltage difference between those different metals is also awarded 3 points.

2018 Chemistry of Cooking Solution

Corrections

  • In part iii of question 3(d), the balanced equation given C18H15 as the formula of the hydrocarbon should be the following:
    4C18H15 + 87O2 → 30H2O + 72CO2.