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 substance can be decomposed chemically?

(A) Ammonia
(B) Iron
(C) Neon
(D) Hydrogen
(E) Fluorine
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 atom is not paired with its correction and ionic charge?

(A) Rb / Rb1-
(B) Mg / Mg2+
(C) F / F1-
(D) Li / Li1+
(E) Br / Br1-
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 7

A solution of which compound gives a violet flame test?

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

An atom has eight electrons in a 3d subshell. How many orbitals in this subshell have an unpaired electron?

(A) 1
(B) 2
(C) 3
(D) 4
(E) 5
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 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

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