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 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

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
Chemistry

Which of the following is not a physical property?

(A) Color
(B) Phase
(C) Odor
(D) Boiling point
(E) Reactivity with oxygen
Chemistry

Which gas is expected to have the highestrate of effusion?

(A) O2
(B) F2
(C) H2O
(D) He
(E) CH2
Chemistry

2019 U.S. National Chemistry Olympiad Local Section Exam Question 16

A two-dimensional slice through the lattice of a crystalline solid containing two different elements X and Y is shown schematically and to scale below. What type of solid is it?

(A) A metallic alloy such as FeCr
(B) A molecular solid such as IBr
(C) An ionic compound such as LiCl
(D) A network covalent solid such as SiC
Chemistry

Which sample represents a homogeneous mixture?

(A) CH3OH(l)
(B) CH3OH(aq)
(C) CH3OH(g)
(D) CH3OH(s)
(E) None of the above
Chemistry

2019 U.S. National Chemistry Olympiad Local Section Exam Question 20

Which sample has the greatest entropy at a given temperature?

(A) 2 mol HBr(s)
(B) 2 mol HBr(l)
(C) 2 mol HBr(g)
(D)  1 mol H2(g) + 1 mol Br2(l)
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 book is lifted off of the floor and placed on a table that is one meter above the floor. The book has

(A) Degree and gram
(B) gained sound energy
(C) gained potential energy
(D) gained kinetic energy
(E) lost nuclear energy