Chapter 17 How Chemicals React
17.1 Chemical Equations
1) Steel wool wetted with vinegar is stuffed into a narrow mouth round glass bottle. A rubber
balloon is then sealed over the mouth of the bottle. After several hours, the balloon inflates into
the bottle in an inverted manner. What happened?
A) Vinegar fumes are diamagnetic and as they accumulate above the liquid the steel wool is
attracted thus inflating the balloon into the mouth of the bottle in an inverted manner.
B) The caustic vinegar fumes get past the steel wool and deteriorate the balloon, which begins to
sag into the bottle and inflate it in an inverted manner.
C) The vinegar reacts with the steel wool by absorbing oxygen within the bottle thus decreasing
the pressure. The greater outside pressure causes the balloon to inflate in an inverted manner.
D) False! The balloon inflates above the mouth of the bottle because the reaction between the
vinegar and steel wool produces a gas which is forced upward because of increased pressure
inside the sealed bottle.
Answer: C
2) Steel wool wetted with vinegar is sealed within a balloon inflated with air. After several hours,
what happens to the volume of the balloon?
A) The balloon inflates.
B) The balloon deflates.
C) The balloon dissolves.
D) Nothing because the vinegar is acting on the steel wool, not upon the balloon.
Answer: B
3) A friend argues that if mass were really conserved he would never need to refill his gas tank.
What explanation do you offer your friend?
A) The atoms (mass) of gasoline are converted into energy by the engine according to E=m .
B) The Law of Conservation of Mass does not apply to reactions involving combustion or
explosion of matter.
C) The atoms (mass) of gasoline are converted into exhaust fumes.
D) The oil companies make gasoline in a way that it gets used up so that we are always required
to replenish it.
Answer: C
4) What is wrong with the following depiction of a chemical reaction?
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.
Answer: C
5) What is a chemical reaction?
A) when one or more new compounds are formed by rearranging atoms
B) when a new element is formed by rearranging nucleons
C) when two solids mix together to form a heterogeneous mixture
D) when two liquids mix to form a homogeneous mixture
E) when a liquid undergoes a phase change and produces a solid
Answer: A
6) What is a chemical equation?
A) It is a shorthand notation for illustrating a chemical reaction.
B) It is the sum of the masses of the products and reactants.
C) It is the chemical combination of equal numbers of reactants and products.
D) It is a picture of the atoms undergoing a chemical equalization.
E) It is any type of reaction that takes place at the equator.
Answer: A
7) Given the following generic chemical reaction, which is the product?
X→Y
A) Y is the product.
B) X is the product.
C) → is the product.
D) Both X and Y are the products.
E) Both X and Y are the reactants.
Answer: A
8) Given the following generic chemical reaction, which is the reactant?
X→Y
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.
Answer: B
9) For the following balanced reaction, which of the following is a solid?
2 Na(l) + Cl2(g) → 2 NaCl(s)
A) Na
B) 2 Na
C) Cl2
D) Cl
E) NaCl
Answer: E
10) For the following balanced reaction, which of the following is a gas?
2 Na(l) + Cl2(g) → 2 NaCl(s)
A) Na
B) 2 Na
C) Cl2
D) Cl
E) NaCl
Answer: C
11) For the following balanced equation, which has the highest coefficient?
4 H2 + 2 C → 2 CH4
A) H2
B) C
C) CH4
D) H4
E) none of the above
Answer: A
12) Balance the following chemical equation.
____ N2 + ____ H2 → ____ NH3
A) 1, 3, 2
B) 1, 2, 3
C) 3, 2, 1
D) 2, 6, 4
E) 1/2, 3/2, 1
Answer: A
13) Balance the following equation.
____ NO → ____ N2O + _____ NO2
A) 3, 1, 1
B) 3, 0, 0
C) 4, 4, 8
D) 1, 2, 4
E) 6, 2, 1
Answer: A
14) Which of the following is a correctly balanced equation?
A) P4 + 6 H2 → 4 PH3
B) 1 P4 + 6 H2 → 4 PH3
C) 0 P4 + 6 H2 → 4 PH3
D) 2 P4 + 12 H2 → 8 PH3
E) P4 + 3 H2 → PH3
Answer: A
15) Balance these equations.
____ H2 (g) + ____ N2 (g) → ____ NH3 (g)
A) 2, 2, 3
B) 2, 2, 5
C) 3, 3, 2
D) 3, 1, 2
Answer: D
16) What coefficients balance the following equation?
____ P4 (s) + ____ H2 (g) → ____ PH3 (g)
A) 4, 2, 3
B) 1, 6, 4
C) 1, 4, 4
D) 2, 10, 8
Answer: B
17) What coefficient is needed in front of the O2 molecule to balance the following equation?
2 C4H10 (g) + _____ O2 (g) → 8CO2 (g) + 10 H2O (l)
A) 8
B) 13
C) 5
D) 1
Answer: B
18) Which equations are balanced?
a) Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g)
b) 3Al (s) + 3 Br2 (l) → Al2Br3 (s)
c) 2HgO (s) → 2 Hg (l) + O2 (g)
A) Only equation "c" is balanced.
B) Equations "a" and "c" are balanced.
C) Equations "b" and "c" are balanced.
D) All of them are balanced.
Answer: B
19) How many diatomic molecules are represented in the illustration above?
A) 1
B) 2
C) 3
D) 4
Answer: B
20) Which equation best describes the reaction represented in the illustration above?
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
Answer: D
21) The reactants shown schematically below represent iron oxide, Fe2O3 and carbon monoxide,
CO. Which of the following is the correct full balanced chemical equation for what is depicted?
A) Fe2O3+ 3 CO → 2 Fe + 3 CO2
B) Fe2O3+ 3 CO → 3 FeO + 2 C
C) Fe2O3 + 3 CO → 3 FeO2 + 2 C
D) Fe2O3+ 3 CO → 2 Fe + 3 C2O
Answer: A
17.2 Counting Atoms and Molecules By Mass
1) Why is it important for a chemist to know the relative masses of atoms?
A) There are not that many different kinds of atoms and so it's important to know how they relate
to one another.
B) It provides information about how many atoms two samples have relative to each other
C) It provides an indication of how the different atoms will interact
D) Because the mass of an atom is directly related to its chemical properties.
Answer: B
2) 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?
A) 1/50
B) 1/20
C) 20 times
D) 100 times
E) 6.022 × 10
23
Answer: A
3) If the relative mass of a pingpong ball is 1/20 that of a golf ball, how many golf balls would
you need to equal the mass of 200 pingpong balls?
A) 10
B) 200
C) 100
D) 20
E) 6.022 × 10
23
Answer: A
4) If it takes three golf balls to equal the mass of one tennis ball, what mass of tennis balls do you
need to equal the number of golf balls in one kilogram of golf balls?
A) 1/3 of a kg
B) 30 kg
C) 1 kg
D) 3 kg
E) 6 kg
Answer: A
5) If it takes three carbon atoms to equal the mass of one chlorine atom, what weight of chlorine
do you need to equal the number of atoms in one kilogram of carbon?
A) 1/3 of a kg
B) 30 kg
C) 1 kg
D) 3 kg
E) 6 kg
Answer: A
6) If the relative mass of a pingpong ball is 1/20 that of a golf ball, how many pingpong balls
would you need to equal the mass of two golf balls?
A) 40
B) 20
C) 24
D) 100
E) 6.022 × 10
23
Answer: A
7) How many oxygen molecules are needed to make 10 carbon dioxide molecules according to
the following balanced chemical equation?
2 CO + O2 → 2 CO2
A) 5
B) 1
C) 4
D) 10
E) 2
Answer: A
8) What is the formula mass of sulfur dioxide, SO2?
A) about 16 amu
B) about 32 amu
C) about 60 amu
D) about 64 amu
Answer: D
9) If the relative mass of a hydrogen atom is 1/4 that of a helium atom, how many helium atoms
would you need to equal the mass of 200 hydrogen atoms?
A) 50
B) 200
C) 800
D) 4
E) 100
Answer: A
10) 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?
A) 16
B) 4
C) 1/4
D) 25
E) 6.022 × 10
23
Answer: A
11) What are the formula masses of water, H2O; propene, C3H6; and 2-propanol, C3H8O?
A) water: 18 amu; propene: 40 amu; 2-propanol: 58 amu
B) water: 18 amu; propene: 42 amu; 2-propanol: 62 amu
C) water: 18 amu; propene: 42 amu; 2-propanol: 60 amu
D) water: 18 amu; propene: 44 amu; 2-propanol: 64 amu
Answer: C
12) If it takes 20 beryllium atoms to equal the mass of two krypton atoms, what is the relative
mass of beryllium compared to krypton?
A) 1/10
B) 1/20
C) 40 times
D) 100 times
E) 10 times
Answer: A
13) Is it possible to have a macroscopic sample of oxygen that has a mass of 14 atomic mass
units?
A) Yes, but it would need to be made of oxygen atoms that each had less than the normal number
of neutrons.
B) No, this is less than than the mass of a single oxygen atom.
C) Yes, but it would have the same density as nitrogen.
D) No, because oxygen is a gas at room temperature.
Answer: B
14) Which is greater: 1.01 amu of hydrogen or 1.01 grams of hydrogen?
A) 1.01 amu of hydrogen is greater than 1.01 grams of hydrogen.
B) 1.01 grams of hydrogen is greater than 1.01 amu of hydrogen
C) 1.01 grams of hydrogen and 1.01 amu of hydrogen have the same mass.
D) Not enough information information is provided.
Answer: B
15) You are given two samples of elements, and each sample has a mass of 10 grams. If the
number of atoms in each of these samples is the same, what must be true of the two elements?
A) The density of the two elements are the same.
B) The elements are likely be located in the same position in the periodic table.
C) Their spectral patterns will likely be identical.
D) all of the above
Answer: D
16) How does formula mass differ from atomic mass?
A) They represent the same thing.
B) The formula mass of a substance is the sum of the atomic masses of the elements is its
chemical formula. The atomic mass is the mass of a single atom.
C) The atomic mass of a substance is the sum of the formula masses of the elements is its
chemical formula. The atomic mass is the mass of a single atom.
D) The formula mass is the mass of the chemical formula and the atomic mass is the mass of the
molecule.
Answer: B
17) What is the formula mass of a molecule of CO2?
A) 44 amu
B) 56 amu
C) 58.9 amu
D) 118 amu
E) none of the above
Answer: A
18) What is the formula mass of a molecule of C6H12O6?
A) 180 amu
B) 24 amu
C) 29 amu
D) 168 amu
E) none of the above
Answer: A
19) The relative mass of carbon is 3/8 that of an oxygen molecule. How many grams of carbon
are needed to have the same number of particles as found in 32 grams of oxygen molecules?
A) 12 g
B) 32 g
C) 3 g
D) 8 g
E) 3/8 g
Answer: A
20) How many grams of water can be formed from the reaction between 10 grams of oxygen and
1 gram of hydrogen?
A) 11 grams of water are formed since mass must be conserved.
B) 10 grams of water are formed since you can't get a greater mass of water produced than
oxygen reacting.
C) 9 grams of water are formed because oxygen and hydrogen react in an 8:1 ratio.
D) No water is formed because there is insufficient hydrogen to react with the oxygen.
Answer: C
21) How many grams of water can be produced by the combination of 8 grams of oxygen and 8
grams of hydrogen?
A) 16 grams
B) 10 grams
C) 9 grams
D) 8 grams
Answer: C
22) How many grams of water can be produced from the combination of 25.0 grams of hydrogen
and 225 grams of oxygen?
A) 250 grams
B) 225 grams
C) 200 grams
D) 25 grams
Answer: B
23) How is Avogadro's number related to the numbers on the periodic table?
A) The atomic mass listed is the mass of Avogadro's number's worth of atoms.
B) The masses are all divisible by Avogadro's number, which gives you the weight of one mole.
C) The periodic table tells you the mass of one atom. From that, and Avogadro's number you
know the number of moles.
D) The periodic table only gives us atomic numbers, not atomic mass.
E) The mass listed is Avogadro's number.
Answer: A
24) What is the mass of one mole of H2?
A) 2 g
B) 1 g
C) 20 g
23
D) 6.022 × 10 g
E) none of the above
Answer: A
25) Which of the following has the greatest number of particles?
A) 1 mole of Na
B) 22.990 g of Na
C) 1 mole of Be
D) 9.012 g of Be
E) All are the same.
Answer: E
26) Which of the following has the greatest mass?
A) 1 mole of Pb
B) 1 mole of H2
C) 1 mole of Be
D) 1 mole of Na
E) All have the same mass.
Answer: A
27) According to the following balanced chemical equation, if you want to generate two moles of
H2O, how many moles of O2 do you need?
2 H2 + O2 → 2 H2O
A) 1
B) 2
C) 1/2
D) 4
E) 6.022 × 10
23
Answer: A
28) 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
A) 1
B) 2
C) 1/2
D) 4
E) 6.022 × 10
23
Answer: E
29) According to the following balanced chemical equation, if you want to generate two moles of
H2O how many grams of O2 do you need?
2 H2 + O2 → 2 H2O
A) 32
B) 16
C) 8
D) 4
E) 6.022 × 10
23
Answer: A
30) What is the number of moles of H2O produced if you combust one mole of CH4 according to
the following balanced equation?
CH4 + 2 O2 → CO2 + 2 H2O
A) 2 moles
B) 4 moles
C) 6 moles
D) 8 moles
E) 1 mole
Answer: A
31) What is the number of moles of H2O produced if you combust 0.5 mole of CH4 according to
the following balanced equation?
CH4 + 2 O2 → CO2 + 2 H2O
A) 2 moles
B) 4 moles
C) 6 moles
D) 8 moles
E) 1 mole
Answer: E
32) What is the number of grams of CO2 produced if you combust 0.50 mole of CH4 according
to the following balanced equation?
CH4 + 2 O2 → CO2 + 2 H2O
A) 22 g
B) 10 g
C) 44 g
D) 32 g
E) 1 g
Answer: A
33) What is the number of molecules of O2 consumed if you combust one mole of CH4 according
to the following balanced equation?
CH4 + 2 O2 → CO2 + 2 H2O
A) 1 molecule
B) 2 molecules
23
C) 6.022 × 10 molecules
24
D) 1.204 × 0 molecules
E) 1 g of molecules
Answer: D
34) Which has the greatest number of molecules?
A) 28 g of nitrogen, N2
B) 32 g of oxygen, O2
C) 32 g of methane, C H4
D) 38 g of fluorine, F2
Answer: C
35) Which has the greatest number of atoms?
A) 28 g of nitrogen, N2
B) 32 g of oxygen, O2
C) 16 g of methane, C H2
D) 38 g of fluorine, F2
Answer: C
36) Two amu equals how many grams?
A) 2 grams
B) 1.661 × 10
-24
grams
-24
C) 3.322 × 10
D) 1.204 × 10
-22
grams
grams
Answer: C
37) What is the mass of an oxygen atom, O, in atomic mass units?
A) 12 amu
B) 16 amu
C) 18 amu
D) 32 amu
Answer: B
38) What is the mass of a water molecule, H2O, in atomic mass units?
A) 2 amu
B) 3 amu
C) 16 amu
D) 18 amu
Answer: D
39) What is the mass of an oxygen atom, O, in grams?
A) 16 grams
24
B) 1.661 × 10- grams
C) 2.66 × 10
-23
grams
D) none of the above
Answer: C
40) What is the mass of a water molecule, H2O, in grams?
A) 18 grams
B) 1.661 × 10
-24
grams
C) 2.99 × 10-23 grams
D) none of the above
Answer: C
41) How many grams of gallium are there in a 145 gram sample of gallium arenside, GaAs?
A) 74.9 g
B) 69.7 g
C) 145 g
23
D) 6.02 × 10 g
Answer: B
42) A 1.00 carat pure diamond has a mass of 0.20 grams. How many carbon atoms are there
within this diamond?
23
A) 6.0 × 10 carbon atoms
22
B) 2.0 × 10 carbon atoms
22
C) 1.0 × 10 carbon atoms
22
D) 6.0 × 10 carbon atoms
Answer: C
43) How many molecules of aspirin (formula mass aspirin = 180.0 amu) are there in a 0.250gram sample?
A) 6.02 × 10
23
B) 8.36 × 10
20
23
C) 1.51× 10
D) More information is needed.
Answer: B
44) Small samples of oxygen gas needed in the laboratory can be generated by any number of
simple chemical reactions, such as
2 KCl O3 (s) → 2 KCl (s) + 3 O2 (g)
What mass of oxygen (in grams) is produced when 122.6 g of KCl O3 (formula mass = 122.6
amu) takes part in this reaction?
A) 32.00 grams
B) 48.00 grams
C) 96.00 grams
D) More information is needed.
Answer: B
45) How many grams of water, H2O, and propene, C3H6, can be formed from the reaction of 6.0
g of 2-propanol, C3H8O?
C3H8O → C3H6 + H2O
2-Propanol Propene Water
A) 6.0 grams of propene, 0.0 grams of water
B) 1.8 grams of propene, 4.2 grams of water
C) 0.0 grams of propene, 6.0 grams of water
D) 4.2 grams of propene, 1.8 grams of water
Answer: D
46) How many moles of water, H2O, are produced from the reaction of 16 grams methane, CH4,
with an unlimited supply of oxygen, O2. How many grams of H2O is this?
CH4 + 2 O2 → CO2 + 2 H2O
A) 0.889 mole, which is 16 grams
B) 2.0 moles of water, which is 32 grams
C) 2.0 moles of water, which is 36 grams
D) 1.0 mole of water, which is 18 grams
Answer: C
17.3 Reaction Rates
1) What is a reaction rate?
A) It is the speed at which reactants are consumed or product is formed.
B) It is the balanced chemical formula that relates the number of product molecules to reactant
molecules.
C) It is the ratio of the masses of products and reactants.
D) It is the ratio of the molecular masses of the elements in a given compound.
E) none of the above
Answer: A
2) Why might increasing the concentration of a set of reactants increase the rate of reaction?
A) You have increased the chances that any two reactant molecules will collide and react.
B) You have increased the ratio of reactants to products.
C) The concentration of reactants is unrelated to the rate of reaction.
D) The rate of reaction depends only on the mass of the atoms and therefore increases as you
increase the mass of the reactants.
E) none of the above
Answer: A
3) Why might increasing the temperature alter the rate of a chemical reaction?
A) The molecules will have a higher kinetic energy and bump into one another harder.
B) The molecules are less reactive at higher temperatures.
C) The molecules will more likely combine with other atoms at high temperature to save space.
D) The density decreases as a function of temperature and this leads to an increase in volume
which drops the rate of reaction.
E) none of the above
Answer: A
4) What is the activation energy?
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
Answer: A
R = reactants P = products
5) For the above energy profiles, which reaction has the highest activation energy?
A) a
B) b
C) c
D) d
E) All have the same activation energy.
Answer: D
6) For the above energy profiles, which reaction has the lowest activation energy?
A) a
B) b
C) c
D) d
E) All have the same activation energy.
Answer: B
7) A refrigerator delays the spoilage of food by
A) killing microorganisms.
B) slowing down the rate of chemical reactions within microorganisms.
C) expanding the water found within microorganisms.
D) diminishing the supply of oxygen to microorganisms.
Answer: B
8) The yeast in bread dough feeds on sugar to produce carbon dioxide. Why does the dough rise
faster in a warmer area?
A) There is a greater number of effective collisions among reacting molecules.
B) Atmospheric pressure decreases with increasing temperature.
C) The yeast tends to "wake up" with warmer temperatures, which is why baker's yeast is best
stored in the refrigerator.
D) The rate of evaporation increases with increasing temperature.
Answer: A
9) Why does a glowing splint of wood burn only slowly in air, but rapidly in a burst of flames
when placed in pure oxygen?
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.
Answer: A
10) Why is heat often added to chemical reactions performed in the laboratory?
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
Answer: D
11) An Alka-Seltzer antacid tablet bubbles vigorously when placed in water but only slowly
when placed in an alcoholic beverage of the same temperature containing a 50:50 mix of alcohol
and water. Propose a probable explanation involving the relationship between the speed of a
reaction and molecular collisions.
A) The alcohol absorbs the carbon dioxide bubbles before they escape the liquid phase.
B) Alcohol molecules are more massive than water molecules, hence they move slower and their
collisions are not as forceful.
C) The tablet reacts with water but not the alcohol.
D) In a 50:50 mix there are fewer water molecules for the antacid molecules to collide with.
Answer: D
12) What can you deduce about the activation energy of a reaction that takes billions of years to
go to completion? How about a reaction that takes only fractions of a second?
A) The activation energy of both these reactions must be very low.
B) The activation energy of both these reactions must be very high.
C) The slow reaction must have a high activation energy while the fast reaction must have a low
activation energy.
D) The slow reaction must have a low activation energy while the fast reaction must have a high
activation energy.
Answer: C
13) Is the synthesis of ozone, O3, from oxygen, O2, an example of an exothermic or endothermic
reaction?
A) exothermic because ultraviolet light is emitted during its formation
B) endothermic because ultraviolet light is emitted during its formation
C) exothermic because ultraviolet light is absorbed during its formation
D) endothermic because ultraviolet light is absorbed during its formation
Answer: D
17.4 Catalysts
1) How does a catalyst increase the rate of a reaction?
A) It lowers the activation energy.
B) It is neither created nor consumed in a reaction.
C) It has nothing to do with the rate of reaction.
D) It increases the energy difference between the reactants and products.
E) It raises the activation energy of the reactants, which makes the reaction proceed faster.
Answer: A
2) If the following graphs are for the same reaction, which one is most likely the one with an
added catalyst?
A) a
B) b
C) c
D) d
E) All have had catalyst added.
Answer: B
3) Which of the following statements about catalysts is NOT true?
A) A catalyst alters the rate of a chemical reaction.
B) A catalyst can be consumed in a reaction as long as it is regenerated.
C) A catalyst can be used to speed up slow reactions.
D) A catalyst does not change the energy of the reactants or the products.
E) All of the above are true.
Answer: E
4) Some reactions are more sluggish than others. To speed up these reactions and save energy
a(n) ________ is sometimes added.
A) catalyst
B) activator
C) heat source
D) exotherm
E) reaction profile
Answer: A
5) The ________ is what needs to be overcome in a reaction so that it can proceed to the
products.
A) activation energy
B) catalyst
C) entropy
D) thermodynamics
E) bond energy
Answer: A
6) Which of the following statements about ozone is true?
A) Ozone in the stratosphere is beneficial.
B) Ozone in the troposphere is a pollutant.
C) Ozone is generated from photochemical reactions of hydrocarbons.
D) none of the above
E) both A and B
Answer: E
7) Which of the following statements accurately describes the action of ozone?
A) It absorbs UV radiation and undergoes fragmentation.
B) It reflects UV radiation back into space.
C) It reflects heat back into space.
D) It emits UV radiation when excited by sunlight.
E) none of the above
Answer: A
8) Why do the natural reactions involving ozone not lead to depletion of the ozone layer?
A) Ozone continually rises from the troposphere.
B) Ozone is too diffuse.
C) Ozone breaks into fragments that can reassemble into more ozone.
D) UV radiation generates more ozone.
E) C and D
Answer: E
9) What is the environmentally unfriendly component of chlorinated fluorocarbons that
ultimately damages ozone?
A) chlorine atoms
B) fluorine atoms
C) carbon atoms
D) molecular fragments of carbon and fluorine
E) all of the above
Answer: A
10) What is the main difficulty in trying to eliminate chlorinated fluorocarbons from the
atmosphere?
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
Answer: A
11) The chlorinated fluorocarbons molecules are acting as a(n) ________ by converting
hundreds of thousands of molecules before they are inactivated.
A) catalyst
B) aerosol
C) active site
D) acid
E) base
Answer: A
12) Since some of the compounds that are destroying ozone are found in nature normally, how is
it possible to tell that the reactive molecules destroying the ozone are due to our actions?
A) They are accompanied by compounds that are only man-made.
B) The compounds only increased in the past few years.
C) The isotope distribution is unique to man-made elements.
D) The chemical composition is different than natural compounds.
E) all of the above
Answer: A
13) How is ozone produced in the upper atmosphere?
A) It forms by reaction of oxygen molecules with UV light.
B) It forms by nuclear decomposition of oxygen.
C) It diffuses from the lower atmosphere.
D) It forms by the reaction of nitric dioxide and oxygen.
E) all of the above
Answer: A
14) Why is there a drastic reduction in ozone in the spring?
A) There is a sudden increase in Cl atoms in the spring.
B) It is warmer in the spring.
C) There are more chlorofluorocarbons in the spring.
D) all of the above
E) only A and B
Answer: A
15) The portion of the atmosphere that filters out 95 percent of the incident UV radiation is the
________.
A) ozone layer
B) stratosphere
C) troposphere
D) aerosol layer
E) particulates
Answer: A
16) A catalytic converter increases the amount of carbon dioxide emitted by an automobile. Is
this good news or bad news?
A) bad news because carbon dioxide contributes to global warming
B) good news because plants thrive on carbon dioxide
C) bad news because the carbon dioxide contributes to acid rain
D) good news because it means more noxious chemicals are not being emitted
Answer: D
17) Carefully examine the following reaction sequence for the catalytic formation of ozone, O 3,
from molecular oxygen, O2. Which chemical compound is behaving as the catalyst?
O2 + 2 NO → 2 N O2
2 N O2 → 2 NO + 2 O
2 O + 2 O2 → 2 O3
A) Nitrogen monoxide, NO
B) Nitrogen dioxide, N O2
C) Oxygen, O2
D) Atomic oxygen, O
Answer: A
18) Many people hear about atmospheric ozone depletion and wonder why we don't simply
replace that which has been destroyed. Knowing about CFCs and how catalysts work, explain
how this would not be a lasting solution.
A) The amount of energy required to create and transport sufficient ozone to the stratosphere
would be cost prohibitive.
B) Governments would be too slow to respond as they argued about who should shoulder the
burden of undertaking such an endeavor.
C) Any ozone we placed into the stratosphere would be destroyed by the same catalytic action
that destroys naturally occurring stratospheric ozone.
D) all of the above
Answer: D
17.5 Energy and Chemical Reactions
1) What is an exothermic reaction?
A) It is a reaction that requires heat as a reactant.
B) It is a reaction where the products have more energy than the reactants.
C) It is a reaction where there is a net adsorption of energy from a reaction.
D) all of the above
E) none of the above
Answer: E
2) What is an endothermic reaction?
A) It is a reaction that requires heat as a reactant.
B) It is a reaction where the products have more energy than the reactants.
C) It is a reaction where there is a net adsorption of energy from a reaction.
D) all of the above
E) none of the above
Answer: D
3) If it takes energy to break bonds and you gain energy in the formation of bonds, how can some
reactions be exothermic while others are endothermic?
A) It is the total amount of energy that matters. Sometimes some bonds are stronger than others
and so you gain or lose energy when you form them.
B) It is the total number of bonds that matters. Sometimes you create more bonds than you break
and since all bonds have same amount of energy you gain or lose energy depending on the
number of bonds.
C) Some reactants have more energetic bonds than others and they will always release energy.
D) Some products have more energy than others and they always require energy to be formed.
E) none of the above
Answer: A
4) Given the following energy profiles, which of the following reactions is endothermic?
R= reactants P = products
A) a
B) b
C) c
D) d
E) none of the above
Answer: D
R = reactants P = products
5) Given that the above energy profiles have the same scale, which of the reactions is the most
exothermic?
A) a
B) b
C) c
D) d
E) none of the above
Answer: A
6) Given that the above energy profiles have the same scale, which of the reactions would
require the most energy?
A) a
B) b
C) c
D) d
E) none of the above
Answer: D
7) How many bonds between nitrogen and hydrogen are formed if you react nitrogen with
hydrogen according to the following reaction?
N2 + 3H2 → 2 NH3
A) 6
B) 2
C) 3
D) 1
E) 8
Answer: A
8) How many moles of H2 bonds are broken if you react nitrogen with hydrogen according to the
following reaction?
N2 + 3H2 → 2 NH3
A) 6
B) 2
C) 3
D) 1
E) 8
Answer: C
9) Given that the bond energy of N2 is 946 kJ/mole, the bond energy of O2 is 498 kJ/mole and
the NO bond energy is 631 kJ/mole, how much energy is required to react 1 mole of nitrogen
molecules according to the following reaction?
N2 + O2 → 2 NO
A) 182 kJ
B) -182 kJ
C) 813 kJ
D) -813 kJ
E) 2075 kJ
Answer: A
10) Which of the following reaction energies is the least exothermic (but still an exothermic
reaction)?
A) 540 kJ/mole
B) -540 kJ/mole
C) 125 kJ/mole
D) -125 kJ/mole
E) not enough information given
Answer: D
11) Which of the following reaction energies is the most endothermic?
A) 540 kJ/mole
B) -540 kJ/mole
C) 125 kj/mole
D) -125 kJ/mole
E) not enough information given
Answer: A
12) Which is higher in an endothermic reaction: the potential energy of the reactants or the
potential energy of the products?
A) The potential energy of the products is higher than the potential energy of the reactants.
B) The potential energy of the reactants is higher than the potential energy of the products.
C) The potential energy of the reactants is the same as the potential energy of the products.
D) In the early stages of the reaction the potential energy of the reactants is higher. In the later
stages, the potential energy of the products is higher.
Answer: A
13) Bond energies increase in going from C-N (lowest) to C-O to C-F (highest). Explain this
trend based upon the atomic sizes of these atoms as deduced from their positions in the periodic
table.
A) In going from nitrogen to oxygen to fluorine the atoms get larger. This means a greater
nuclear charge, which translates into stronger chemical bonds.
B) In going from nitrogen to oxygen to fluorine the atoms get smaller. This means a greater
nuclear charge, which translates into stronger chemical bonds.
C) In going from nitrogen to oxygen to fluorine the atoms get larger. This means that the
bonding atoms are farther apart, which translates into a greater bond energy.
D) In going from nitrogen to oxygen to fluorine the atoms get smaller. This means that the
bonding atoms are closer together, which translates into a greater bond energy.
Answer: D
14) Are the chemical reactions that take place in a disposable battery exothermic or
endothermic? Is the reaction going on in a rechargeable battery while it is recharging exothermic
or endothermic?
A) An operating disposable battery is driven by endothermic reaction, while a recharging
rechargeable battery is also driven by endothermic reactions.
B) An operating disposable battery is driven by exothermic reaction, while a recharging
rechargeable battery is driven by endothermic reactions.
C) An operating disposable battery is driven by endothermic reaction, while a recharging
rechargeable battery is driven by exothermic reactions.
D) An operating disposable battery is driven by exothermic reaction, while a recharging
rechargeable battery is also driven by exothermic reactions.
Answer: B
15) Use the bond energies below to determine whether the following reaction is exothermic or
endothermic:
H2 + Cl2 → 2 HCl
H-H (bond energy: 436 kJ/mol)
Cl-Cl (bond energy: 243 kJ/mol)
H-Cl (bond energy: 431 kJ/mol)
A) Exothermic with more than 50 kJ of energy released.
B) Endothermic with more than 50 kJ of energy absorbed.
C) Exothermic with less than 50 kJ of energy released.
D) Endothermic with less than 50 kJ of energy absorbed.
Answer: A
16) How much energy, in kilojoules, is released or absorbed from the reaction of one mole of
nitrogen, N2, with three moles of molecular hydrogen, H2, to form two moles of ammonia, NH3?
H-N (bond energy: 389 kJ/mol)
H-H (bond energy: 436 kJ/mol)
N N (bond energy: 946 kJ/mol)
A) +899 kJ/mol absorbed
B) -993 kJ/mol released
C) +80 kJ/mol absorbed
D) -80 kj/mol released
Answer: D
17.6 Chemical Reactions Are Driven By Entropy
1) Which of the following statements best describes the concept of entropy?
A) Energy has a tendency to disperse.
B) Energy is neither created nor destroyed.
C) The entropy of the universe is constantly decreasing.
D) The energy released in a chemical reaction is the same as the difference in the energy of the
bonds broken and formed.
E) Energy has a tendency to remain in one place.
Answer: A
2) What role does entropy play in chemical reactions?
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.
Answer: D
3) Why does iodine, I2 (s), spontaneously sublime at room temperature?
A) The contact of iodine, I2 (s), with the water vapor in the air causes the sublimation process.
B) Iodine, I2 (s), pulls O2 from the air as it self-oxidizes under sublimation to I2 (g).
C) There is an increase in entropy as solid iodine, I2 (s), sublimes into iodine vapor, I2 (g),
because in the gaseous phase energy is more readily dispersed.
D) The reaction of I2 (s) subliming to I2 (g) is highly exothermic and therefore proceeds
spontaneously.
Answer: C
4) Wild plants readily grow "all by themselves" yet the molecules of the growing plant have less
entropy than the materials used to make the plant. How is it possible for a there to be this
decrease in entropy for a process that occurs all by itself?
A) A decrease in entropy does not necessarily mean that a reaction if favored to proceed on its
own. It happens in this instance but not in others.
B) There is no decrease in entropy when wild plants grow. All growing plants tend to display an
increase in entropy.
C) Wild plants don't grow "all by themselves." When we consider the entire system, including
the sun, we find an overall increase in entropy.
D) Life on Earth "arises on its own." It does not depend on entropy processes.
Answer: C
Test Bank for Conceptual Physical Science
Paul Hewitt, John Suchocki, Leslie Hewitt
9780321752932, 9780134060491
