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 4

First-generation automobile airbags were inflated by the decomposition of sodium azide (M = 65.02):

What mass of sodium azide would be required to inflate a 16.0 L airbag to a pressure of 1.20 atm at 17 ºC?

(A) 34.9 g
(B) 52.4 g
(C) 78.6 g
(D) 157 g
Chemistry

2019 U.S. National Chemistry Olympiad Local Section Exam Question 2

Lithium hydrogen carbonate, LiHCO3, decomposes when heated to form Li2O, CO2, and H2O.
How many moles of H2O are formed when 0.50 mol LiHCO3 decomposes?

(A) 0.25 mol
(B) 0.50 mol
(C) 0.75 mol
(D) 1.0 mol
Chemistry

Which of the following is not a conclusion Rutherford made from his experiment with alpha particles being shot at a thin sheet of gold foil?

(A) An atom has a very small, compact nucleus.
(B) An atom is mainly empty space.
(C) An atom’s mass is concentrated in the nucleus.
(D) An atom has a very dense nucleus.
(E) An atom has a negatively charged nucleus.
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

Which is inconsistent with the Kinetic Molecular Theory?

(A) Gas molecules have forces of attraction for each other.
(B) Gas molecules move in a random, straight-line motion.
(C) Gas molecules have a negligible volume compared to the volume they occupy.
(D) Collisions between gas molecules lead to a transfer of energy that is conserved.
(E) All of the above statements are correct.
Chemistry

2019 U.S. National Chemistry Olympiad Local Section Exam Question 22

For a constant-pressure process, what is the difference between the internal energy change (∆U) and the enthalpy change (∆H)?

(A) Heat
(B) Work
(C) Entropy
(D) Gibbs free energy
Chemistry

What is the mass of an object that has a density of 13 g/mL and a volume of 10 mL?

(A) 1.3 g/mL
(B) 0.77 g/mL
(C) 1.3 g/L
(D) 130 g
(E) 130 g/L
Chemistry

A liquid will boil when

(A) its freezing point is equal to its melting point
(B) a salt has been added to the liquid
(C) its vapor pressure is equal to the melting point
(D) it is heated to a temperature that is below the boiling point
(E) its vapor pressure is equal to the surrounding pressure
Chemistry

A solid, liquid, and gas can exist together at the

(A) sublimation point
(B) triple point
(C) boiling point
(D) freezing point
(E) melting point