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

Which principal energy level has exactly four subshells?

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

Which gas under a high temperature and a low pressure behaves most like an ideal gas?

(A) He
(B) O2
(C) NH3
(D) CO2
(E) Ne
Chemistry

2019 U.S. National Chemistry Olympiad Local Section Exam Question 15

In which are the ionic solids ranked in order of increasing melting point?

(A) KBr < NaCl < NaF < MgO
(B) NaF < NaCl < MgO < KBr
(C) KBr < NaCl < MgO < NaF
(D) MgO < NaF < KBr < NaCl
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 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 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 1

Which hydrocarbon is 84.1% carbon by mass?

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