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 pair of symbols below show different isotopes of the same element?

(A) 3918A and 3919R
(B) 6027X and 5928Y
(C) 126L and 146L
(D) 3717X and 3717X
(E) 32E and 31G
Chemistry

Which of the following isotopes has the greatest number of neutrons?

(A) 35Cl
(B) 31P
(C) 40Ar
(D) 41Ca
(E) 14C
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 7

A solution of which compound gives a violet flame test?

(A) LiBr
(B) NaCl
(C) KNO3
(D) B(OH)3
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

Which units could be used to express the amount of energy absorbed or released during a chemical reaction?

(A) Degree and gram
(B) Torr and mmHg
(C) Gram and liter
(D) Calorie and joule
(E) Meter and cm3
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

2019 U.S. National Chemistry Olympiad Local Section Exam Question 17

A portion of the phase diagram of uranium hexafluoride (UF6) is shown below.

Which statements are correct?

I.  UF6 sublimes at atmospheric pressure.
II. At 80 ºC and 1.5 atm, only UF6(g) is present at equilibrium.
(A) I only
(B) II only
(C) Both I and II
(D) Neither I nor II
Chemistry

Which substance can be decomposed chemically?

(A) Ammonia
(B) Iron
(C) Neon
(D) Hydrogen
(E) Fluorine