Chemistry

2019 U.S. National Chemistry Olympiad Local Section Exam Question 8

Addition of 1 M HBr to 0.1 M solutions of which compound results in evolution of a colorless gas?

(A) NaHSO3
(B) NaHSO4
(C) Ce(NH4)2(NO3)6
(D) KBrO3
Chemistry

2019 U.S. National Chemistry Olympiad Local Section Exam Question 1

Which hydrocarbon is 84.1% carbon by mass?

(A) CH4
(B) C2H6
(C) C4H10
(D) C8H18
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 19

The specific heat capacity of iron is 0.461 J g–1 K–1 and that of titanium is 0.544 J g–1 K–1 . A sample consisting of a mixture of 10.0 g Fe and 10.0 g Ti at 100.0 ºC loses 200. J of heat to the environment. What is the final temperature of the sample?

(A) 89.9 ºC
(B) 80.1 ºC
(C) 60.2 ºC
(D) 39.8 ºC
Chemistry

Which statement is incorrect regarding energy?

(A) Energy can be given off in a reaction.
(B) Energy can be gained in a reaction.
(C) Energy cannot be created or destroyed.
(D) Energy can take various forms.
(E) Energy has mass and takes up space.
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

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

2019 U.S. National Chemistry Olympiad Local Section Exam Question 5

Which of the following combinations will produce a 0.4 M NaCl solution?

(A) Mixing 500 mL of 0.4 M NaOH with 500 mL of 0.4 M HCl
(B) Mixing 300 mL of 1.2 M NaOH with 600 mL of 0.6 M HCl
(C) Mixing 500 mL of 0.4 M NaCl solution with 500 mL water
(D) Diluting 400 mL of 0.6 M NaCl with water to a final volume of 1.0 L
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 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