Chemistry

At which temperature does a water sample have the highest average kinetic energy?

(A) 0 degrees Celsius
(B) 100 degrees Celsius
(C) 0 K
(D) 100 K
(E) 273 K
Chemistry

Which type of change is different from the other four?

(A) Baking a potato
(B) Rusting of an iron nail
(C) Burning a piece of paper
(D) Melting an ice cube
(E) Ignition of propane
Chemistry

An ideal gas at STP occupies 22.4 liters. If the pressure on the gas is increased to 1000 torr and the temperature of the gas is reduced to 250 K, what can be said about the gas?

(A) The number of moles of the gas has changed.
(B) The volume of the gas has increased.
(C) The volume of the gas has decreased.
(D) The pressure and the temperature have an inversely proportional relationship.
(E) None of the above.
Chemistry

Which sample demonstrates particles arranged in a regular geometric pattern?

(A) CO2(g)
(B) CO2(s)
(C) CO2(l)
(D) CO2(aq)
(E) None of the above
Chemistry

2019 U.S. National Chemistry Olympiad Local Section Exam Question 24

The Ksp of BaSO4 at 298 K is 1.1 × 10–10. What is ∆ at 298 K for the following reaction?

(A)  –57 kJ mol–1
(B)  –25 kJ mol–1
(C) 25 kJ mol–1
(D) 57 kJ mol–1
Chemistry

2019 U.S. National Chemistry Olympiad Local Section Exam Question 13

Which gas at 600 K has the same effusion rate as methane (CH4) at 150 K?

(A) He
(B) O2
(C) SO2
(D) N2O4
Chemistry

Which electron conguration demonstrates an atom in the excited state?

(A) 1s22s1
(B) 1s22s22p4
(C) 1s22s2
(D) 1s22s22p63s2
(E) 1s22s23s1
Chemistry

2019 U.S. National Chemistry Olympiad Local Section Exam Question 9

Which solid is least soluble in water at 298 K?

(A) CaF2
(B) AgF
(C) Ba(OH)2
(D) CoSO4
Chemistry

2019 U.S. National Chemistry Olympiad Local Section Exam Question 6

Which solute, when dissolved in 1 kg H2O, will give the solution with the highest boiling point?

(A) 50 g ethylene glycol, HOCH2CH2OH
(B) 50 g hydroxyacetic acid, HOCH2COOH
(C) 50 g glycerol, HOCH2CHOHCH2OH
(D) 50 g glyoxal, HCOCHO
Chemistry

2019 U.S. National Chemistry Olympiad Local Section Exam Question 11

The concentration of sulfate ion in a solution is measured by precipitating the sulfate as BaSO4, filtering the precipitate on ashless filter paper, and heating the filter paper and precipitate in a tared crucible with a Bunsen burner. Which error will result in a sulfate concentration that is higher than the actual concentration?

(A) The empty crucible contains a few drops of water when it is tared.
(B) A glass fiber filter is used instead of ashless filter paper.
(C) Some fine precipitate is not captured by the filter.
(D) Some of the sulfate-containing solution spills before the BaCl2 solution is added.