Question 1

If the relative mass of a hydrogen atom is 1/4 that of a helium atom, how many hydrogen atoms would you need to equal the mass of four helium atoms?

Accepted Answer

A) 16 
B) 4 
C) 1/4 
D) 25 
E) 6.022 × 1023 
A) 16 
B) 4 
C) 1/4 
D) 25 
E) 6.022 × 1023

Question 2

Which of the following reaction energies is the most endothermic?

Accepted Answer

A) 540 kJ/mole 
B) -540 kJ/mole 
C) 125 kj/mole 
D) -125 kJ/mole 
E) not enough information given 
A) 540 kJ/mole 
B) -540 kJ/mole 
C) 125 kj/mole 
D) -125 kJ/mole 
E) not enough information given

Question 3

If it takes 200 golf balls to equal the mass of four bowling balls, what is the relative mass of bowling balls to golf balls?

Accepted Answer

A) 1/50 
B) 1/20 
C) 20 times 
D) 100 times 
E) 6.022 × 1023  
A) 1/50 
B) 1/20 
C) 20 times 
D) 100 times 
E) 6.022 × 1023

Question 4

What is the main difficulty in trying to eliminate chlorinated fluorocarbons from the atmosphere?

Accepted Answer

A) They are very stable and take a long time to decompose completely. 
B) They are too light and blow away. 
C) They do not absorb ultraviolet radiation. 
D) all of the above 
E) only a and b 
A) They are very stable and take a long time to decompose completely. 
B) They are too light and blow away. 
C) They do not absorb ultraviolet radiation. 
D) all of the above 
E) only a and b

Question 5

Given the following generic chemical reaction, which is the reactant? X → Y

Accepted Answer

A) Y is the reactant. 
B) X is the reactant. 
C) → is the reactant. 
D) Both X and Y are the products. 
E) Both X and Y are the reactants. 
A) Y is the reactant. 
B) X is the reactant. 
C) → is the reactant. 
D) Both X and Y are the products. 
E) Both X and Y are the reactants.

Question 6

If the following graphs are for the same reaction, which one is most likely the one with an added catalyst?

Accepted Answer

A) a 
B) b 
C) c 
D) d 
E) All have had catalyst added. 
A) a 
B) b 
C) c 
D) d 
E) All have had catalyst added.

Question 7

Which of the following reaction energies is the least exothermic (but still an exothermic reaction)?

Accepted Answer

A) 540 kJ/mole 
B) -540 kJ/mole 
C) 125 kJ/mole 
D) -125 kJ/mole 
E) not enough information given 
A) 540 kJ/mole 
B) -540 kJ/mole 
C) 125 kJ/mole 
D) -125 kJ/mole 
E) not enough information given

Question 8

Why does a glowing splint of wood burn only slowly in air, but rapidly in a burst of flames when placed in pure oxygen?

Accepted Answer

A) There is a greater number of collisions between the wood and oxygen molecules. 
B) Oxygen is a flammable gas. 
C) Pure oxygen is able to absorb carbon dioxide at a faster rate. 
D) A glowing wood splint is actually extinguished within pure oxygen because there's no room for the smoke to expand. 
A) There is a greater number of collisions between the wood and oxygen molecules. 
B) Oxygen is a flammable gas. 
C) Pure oxygen is able to absorb carbon dioxide at a faster rate. 
D) A glowing wood splint is actually extinguished within pure oxygen because there's no room for the smoke to expand.

Question 9

How many diatomic molecules are represented in the illustration above?

Accepted Answer

A) 1 
B) 2 
C) 3 
D) 4 
A) 1 
B) 2 
C) 3 
D) 4

Question 10

What is wrong with the following depiction of a chemical reaction?

Accepted Answer

A) These boxes contain only molecules but no atoms. 
B) One box contains more molecules than the other. 
C) One box contains more atoms than the other. 
D) All of the above. 
A) These boxes contain only molecules but no atoms. 
B) One box contains more molecules than the other. 
C) One box contains more atoms than the other. 
D) All of the above.

Question 11

How many molecules of aspirin (formula mass aspirin = 180.0 amu)are there in a 0.250-gram sample?

Accepted Answer

A) 6.02 × 1023 
B) 8.36 × 1020 
C) 1.51× 1023 
D) More information is needed. 
A) 6.02 × 1023 
B) 8.36 × 1020 
C) 1.51× 1023 
D) More information is needed.

Question 12

For the above energy profiles, which reaction has the highest activation energy?

Accepted Answer

A) a 
B) b 
C) c 
D) d 
E) All have the same activation energy. 
A) a 
B) b 
C) c 
D) d 
E) All have the same activation energy.

Question 13

Why is heat often added to chemical reactions performed in the laboratory?

Accepted Answer

A) to allow a greater number of reactants to pass over the activation energy 
B) to increase the rate at which reactant collide 
C) to compensate for the natural tendency of energy to disperse 
D) all of the above 
A) to allow a greater number of reactants to pass over the activation energy 
B) to increase the rate at which reactant collide 
C) to compensate for the natural tendency of energy to disperse 
D) all of the above

Question 14

What role does entropy play in chemical reactions?

Accepted Answer

A) The entropy determines how much product will actually be produced. 
B) The entropy change determines whether the reaction will be exothermic or endothermic. 
C) The entropy change determines whether the reaction will occur spontaneously or not. 
D) The entropy change determines whether or not the chemical reaction is favorable. 
A) The entropy determines how much product will actually be produced. 
B) The entropy change determines whether the reaction will be exothermic or endothermic. 
C) The entropy change determines whether the reaction will occur spontaneously or not. 
D) The entropy change determines whether or not the chemical reaction is favorable.

Question 15

According to the following balanced chemical equation, if you want to generate two moles of H2O , how many molecules of O2 do you need? 2 H2 + O2 → 2 H2O

Accepted Answer

A) 1 
B) 2 
C) 1/2 
D) 4 
E) 6.022 × 1023 
A) 1 
B) 2 
C) 1/2 
D) 4 
E) 6.022 × 1023

Question 16

Balance the following equation. ____ NO → ____ N2O + _____ NO2

Accepted Answer

A) 3, 1, 1 
B) 3, 0, 0 
C) 4, 4, 8 
D) 1, 2, 4 
E) 6, 2, 1 
A) 3, 1, 1 
B) 3, 0, 0 
C) 4, 4, 8 
D) 1, 2, 4 
E) 6, 2, 1

Question 17

Which equation best describes the reaction represented in the illustration above?

Accepted Answer

A) 2 AB2 + 2 DCB3 + B2 → 2 DBA4 + 2 CA2 
B) 2 AB2 + 2 CDA3 + B2 → 2 C2A4 + 2 DBA 
C) 2 AB2 + 2 CDA3 + A2 → 2 DBA4 + 2 CA2 
D) 2 BA2 + 2 CDA3 + A2 → 2 DBA4 + 2 CA2 
A) 2 AB2 + 2 DCB3 + B2 → 2 DBA4 + 2 CA2 
B) 2 AB2 + 2 CDA3 + B2 → 2 C2A4 + 2 DBA 
C) 2 AB2 + 2 CDA3 + A2 → 2 DBA4 + 2 CA2 
D) 2 BA2 + 2 CDA3 + A2 → 2 DBA4 + 2 CA2

Question 18

What is the activation energy?

Accepted Answer

A) the minimum amount of energy to break the bonds in reactants 
B) the amount of energy required to activate a phase change 
C) the energy difference between the reactants and the products 
D) the amount of energy required to separate reactants from the products 
E) the hill 
A) the minimum amount of energy to break the bonds in reactants 
B) the amount of energy required to activate a phase change 
C) the energy difference between the reactants and the products 
D) the amount of energy required to separate reactants from the products 
E) the hill

Exam 17: How Chemicals React

If the relative mass of a hydrogen atom is 1/4 that of a helium atom, how many hydrogen atoms would you need to equal the mass of four helium atoms?

Which of the following reaction energies is the most endothermic?

If it takes 200 golf balls to equal the mass of four bowling balls, what is the relative mass of bowling balls to golf balls?

What is the main difficulty in trying to eliminate chlorinated fluorocarbons from the atmosphere?

Given the following generic chemical reaction, which is the reactant? X → Y

If the following graphs are for the same reaction, which one is most likely the one with an added catalyst?

Which of the following reaction energies is the least exothermic (but still an exothermic reaction)?

Why does a glowing splint of wood burn only slowly in air, but rapidly in a burst of flames when placed in pure oxygen?

How many diatomic molecules are represented in the illustration above?

What is wrong with the following depiction of a chemical reaction?

How many molecules of aspirin (formula mass aspirin = 180.0 amu)are there in a 0.250-gram sample?

For the above energy profiles, which reaction has the highest activation energy?

Why is heat often added to chemical reactions performed in the laboratory?

What role does entropy play in chemical reactions?

According to the following balanced chemical equation, if you want to generate two moles of H2O , how many molecules of O2 do you need? 2 H2 + O2 → 2 H2O

Balance the following equation. ____ NO → ____ N2O + _____ NO2

Which equation best describes the reaction represented in the illustration above?

What is the activation energy?

Patterns of Motion and Equilibrium

Newtons Laws of Motion

Momentum and Energy

Gravity, Projectiles, and Satellites

Fluid Mechanics

Thermal Energy and Thermodynamics

Heat Transfer and Change of Phase

Static and Current Electricity

Magnetism and Electromagnetic Induction

Waves and Sound

Light

Atoms and the Periodic Table

The Atomic Nucleus and Radioactivity

Elements of Chemistry

How Atoms Bond and Molecules Attract

Mixtures

Two Classes of Chemical Reactions

Organic Compounds

Rocks and Minerals

Plate Tectonics and Earths Interior

Shaping Earths Surface

Geologic Timereading the Rock Record

The Oceans, Atmosphere, and Climatic Effects

Driving Forces of Weather

The Solar System

Stars and Galaxies

The Structure of Space and Time

Prologue: the Nature of Science

Filters

According to the following balanced chemical equation, if you want to generate two moles of H₂O , how many molecules of O₂ do you need? 2 H₂ + O₂ → 2 H₂O

Balance the following equation. NO → N₂O + _ NO₂