Chapter 18 Two Classes of Chemical Reactions
18.1 Acids Donate Protons and Bases Accept Them
1) How do you make a proton out of a hydrogen atom?
A) remove an electron from a hydrogen atom
B) remove a proton from a helium nucleus
C) let the hydrogen atoms undergo fusion
D) let the hydrogen atoms combine to form a hydrogen molecule and eject an electron
E) let the hydrogen atoms combine to form a hydrogen molecule and eject a proton
Answer: A
2) Which of the following compounds would least likely act as an acid?
A) SO4
-2
B) HSO4
-1
C) H2SO4
D) NH3
E) CH3CO2H
Answer: A
3) What is an acid?
A) Anything that donates hydrogen ions.
B) Anything that accepts hydrogen atoms.
C) Anything that donates hydrogen atoms.
D) Anything that dissolves metal.
E) Anything that donates hydronium ions.
Answer: A
4) What is a base?
A) Anything that accepts a hydrogen ion.
B) Anything that accepts a hydroxide ion.
C) Anything that donates a hydroxide ion.
D) Anything that can be used to clean drains.
E) Anything with a bitter taste.
Answer: A
5) What best describes what happens when an acid such as HCl is mixed with water?
A) The proton chemically bonded to the chlorine is transferred to a water molecule and forms a
chloride ion and a hydronium ion.
B) A proton from the chlorine nucleus is ejected and captured by a water molecule to form a
negatively charged HCl and a new hydronium ion.
C) A hydroxide ion from the water is transferred to the HCl molecule to form a proton and
hydronium ion.
D) HCl is not an acid.
E) none of the above
Answer: A
6) According to the following reaction, which molecule is acting as an acid?
+
H2O + H2SO4 → H3O + HSO4A) H2SO4
B) H2O
+
C) H3O
D) HSO4E) none of the above
Answer: A
7) According to the following reaction, which molecule is acting as a base?
+
H2O + H2SO4 → H3O + HSO4A) H2SO4
B) H2O
+
C) H3O
D) HSO4E) none of the above
Answer: B
8) According to the following reaction, which molecule is acting as an acid?
+
H3O + HSO4- → H2O + H2SO4
A) H2SO4
B) H2O
+
C) H3O
D) HSO4E) none of the above
Answer: C
9) According to the following reaction, which molecule is acting as a base?
+
H3O + HSO4- → H2O + H2SO4
A) H2SO4
B) H2O
+
C) H3O
D) HSO4E) none of the above
Answer: D
10) According to the following reaction, which molecule is acting as a base?
-
H2O + NH3 → OH + NH4+
A) H2O
B) NH3
C) OH
-
D) NH4+
E) none of the above
Answer: B
11) According to the following reaction, which molecule is acting as an acid?
-
H2O + NH3 → OH + NH4+
A) H2O
B) NH3
C) OH-
D) NH4+
E) none of the above
Answer: A
12) According to the following reaction, which molecule is acting as an acid?
+
OH- + NH4 → H2O + NH3
A) H2O
B) NH3
C) OHD) NH4
+
E) none of the above
Answer: D
13) According to the following reaction, which molecule is acting as a base?
+
OH- + NH4 → H2O + NH3
A) H2O
B) NH3
C) OHD) NH4+
E) none of the above
Answer: C
14) In the reaction below, what does the symbol ⇌ mean?
A) It means that the forward and backward reactions are happening at the same time.
B) It means that the reaction cannot decide which way to go.
C) It means that the forward reaction does not progress.
D) It means that the backward reaction happens as fast as the forward reaction and so the proton
is not transferred at all.
E) none of the above
Answer: A
15) For the following reaction, identify whether the compound in bold is behaving as an acid or a
base.
+
H3PO4 + H2O ⇌ H2PO4- + H3O
A) acid
B) base
C) neither
D) both
E) none of the above
Answer: A
16) For the following reaction, identify whether the compound in bold is behaving as an acid or a
base.
+
H3PO4 + H2O ⇌ H2PO4- + H3O
A) acid
B) base
C) neither
D) both
E) none of the above
Answer: B
17) For the following reaction, identify whether the compound in bold is behaving as an acid or a
base.
+
H3PO4 + H2O ⇌ H2PO4- + H3O
A) acid
B) base
C) neither
D) both
E) none of the above
Answer: B
18) For the following reaction, identify whether the compound in bold is behaving as an acid or a
base.
+
H3PO4 + H2O ⇌ H2PO4- + H3O
A) acid
B) base
C) neither
D) both
E) none of the above
Answer: A
19) For the following acid-base reaction, identify which salt is formed.
HCl + NaOH ⇌ ???? + H2O
A) NaCl
B) H3OCl
C) NaOH2
D) NaOH2Cl
E) none of the above
Answer: A
20) For the following acid-base reaction, identify what compound is formed in the space marked.
HCl + KOH ⇌ ???? + H2O
A) KCl
B) H3OCl
C) KOH2
D) KOH2Cl
E) none of the above
Answer: A
21) For the following acid-base reaction, identify what is formed in the space marked.
HF + KOH ⇌ ???? + H2O
A) KF
B) H3OF
C) KOH2
D) KOH2F
E) none of the above
Answer: A
22) For the following acid-base reaction, identify what compound is formed in the space marked.
HNO3 + KOH ⇌ ???? + H2O
A) KNO3
B) H3ONO3
C) KOH2
D) KOH2NO3
E) none of the above
Answer: A
23) For the following acid-base reaction, identify what is formed in the space marked.
H2SO4 + KOH ⇌ KHSO4 + ???
A) K2SO4
B) H3OSO4
C) H2O
D) KOH2SO4
E) none of the above
Answer: C
24) Which of the following statements is not true about a neutralization reaction?
A) Water is always formed in a neutralization reaction.
B) One molecule of acid neutralizes one molecule of base.
C) A neutralization is the reaction of a hydroxide ion with a proton.
D) All of the above are true.
E) None of the above are true.
Answer: E
25) Suggest why people once washed their hands with ashes.
A) The ashes act as a base and reacts with skin oils to produce solutions of soap.
B) The ashes act as an acid and reacts with the skin oils to produce soap.
C) The oils on the skin act as a base and reacts with the ashes to produce soap.
D) After being burnt in the fire, the acids and bases of the log are neutralized, making it a gentle
material to use on the hands.
Answer: A
26) What is the relationship between the hydroxide ion and a water molecule?
A) A hydroxide ion is a water molecule plus a proton.
B) A hydroxide ion and a water molecule are the same things.
C) A hydroxide ion is a water molecule minus a hydrogen nucleus.
D) A hydroxide ion is a water molecule plus two extra electrons.
Answer: C
27) An acid and a base react to form a salt, which consists of positive and negative ions. Which
forms the positive ions: the acid or the base? Which forms the negative ions?
A) The acid forms the positive ion, the base forms the negative ion.
B) The acid forms the negative ion, the base forms the positive ion.
C) Because different substances can act as an acid or a base, it depends on the substance you
begin with.
D) all of the above
Answer: B
28) Water is formed from the reaction of an acid and a base. Why is it not classified as a salt?
A) Not all acid base reactions produce a salt, as in the case with the formation of water.
B) The attraction between the two ions in water molecules are too strong.
C) By definition, a salt must be able to dissolve in water, so water itself cannot be called a salt.
D) A salt is an ionic compound, whereas water is a covalent compound.
Answer: D
29) Identify the acid or base behavior of each substance in these reactions:
H3O+ + Cl- ⇌ H2O + HCl
+
-
+
-
+
-
A) H3O acts as an acid, Cl acts as a base, H2O acts an acid, HCl acts as a base.
B) H3O acts as an base, Cl acts as a acid, H2O acts an acid, HCl acts as a base.
C) H3O acts as an acid, Cl acts as a base, H2O acts an base, HCl acts as a acid.
+
D) H3O acts as an base,
acts as a acid, H2O acts an base, HCl acts as an acid.
Answer: C
30) Identify the acid or base behavior of each substance in these reactions:
-
A) HS O4- acts as an acid, H2O acts as a base, OH acts as an acid, H2S O4 acts as a base.
-
B) HS O4- acts as an base, H2O acts as a acid, OH acts as an acid, H2S O4 acts as a base.
-
C) HS O4- acts as an acid, H2O acts as a base, OH acts as an base, H2S O4 acts as a acid.
-
D) HS O4- acts as an base, H2O acts as a acid, OH acts as an base, H2S O4acts as a acid.
Answer: D
31) What happens to the corrosive properties of an acid and a base after they neutralize each
other? Why?
A) The corrosive properties are neutralized because the acid and base no longer exist.
B) The corrosive properties are unaffected because salt is a corrosive agent.
C) The corrosive properties are doubled because the acid and base are combined in the salt.
D) The corrosive properties remain the same when the salt is mixed into water.
Answer: A
32) The main component of bleach is sodium hypochlorite, NaOCl, which consists of sodium
ions, Na⁺, and hypochlorite ions, -OCl What products are formed when this compound is reacted
with the hydrochloric acid, HCl, of toilet bowl cleaner?
A) The products are NaCl, O2, and HClO2.
B) The products are NaOH, H2O, and Cl2
C) The products are NaCl and HOCl.
D) The products are NaOH, O2, and Cl2
Answer: C
18.2 Relative Strengths of Acids and Bases
1) Which of the following statements about strong or weak acids is true?
A) A weak acid and a strong acid at the same concentration are equally corrosive.
B) A weak acid readily forms ions when dissolved in water.
C) A strong acid will never react with a strong base.
D) A weak acid will react with a strong base.
Answer: D
2) Which of the following statements about strong or weak bases is true?
A) A weak base completely separates into ions in water.
B) A weak base will not react with a strong acid.
C) A strong base is always corrosive.
D) A strong base will readily accept protons from even weak acids.
Answer: D
3) What is the main characteristic of a strong acid?
A) It is completely dissociated in water.
B) It readily gives up its proton to a base.
C) It is corrosive.
D) It will damage your skin.
E) all of the above
Answer: E
4) What is the main characteristic of a strong base?
A) It is completely dissociated in water.
B) It readily accepts an acidic proton.
C) It is corrosive.
D) It will damage your skin.
E) all of the above
Answer: E
5) Which of the following statements about strong and weak acids is not true?
A) A weak acid is as corrosive as a strong acid.
B) A weak acid dissociates in water.
C) A strong acid will react with a strong base.
D) A weak acid will react with a strong base.
E) All of the above are untrue.
Answer: A
6) Which of the following statements about strong and weak bases is not true?
A) A weak base does not completely dissociate in water.
B) A weak base will not react with a strong acid.
C) A strong base can be extremely corrosive.
D) A strong base will readily accept protons from even weak acids.
E) All of the above are untrue.
Answer: B
7) Which of the above images would best describe a water solution of a weak acid (HA) the
best?
A) A
B) B
C) C
D) All of the above are weak acids.
E) None of the above are weak acids.
Answer: B
8) Which of the above images represents a solution of the strongest acid (HA)?
A) A
B) B
C) C
D) All of the above are strong acids.
E) None of the above are strong acids.
Answer: C
9) Arrange the following images of an aqueous base solution in order of increasing base strength:
A) A, B, C
B) B, C, A
C) C, B, A
D) A, C, B
E) All are equally strong.
Answer: A
10) Sodium hydroxide, NaOH, is a strong base, which means that it readily accepts hydrogen
ions. What products are formed when sodium hydroxide accepts a hydrogen ion from a water
molecule?
A) water and sodium hydroxide
B) sodium hydroxide and hydronium ions
C) sodium ions and hydronium ions
D) sodium ions and water
Answer: A
11) A weak acid is added to a concentrated solution of hydrochloric acid. Does the solution
become more or less acidic?
A) More acidic, since there are more hydronium ions being added to the solution.
B) Less acidic, since the solution becomes more dilute with a less concentrated solution of
hydronium ions being added to the solution.
C) No change in acidity, since the concentration of the hydrochloric acid is too high to be
changed by the weak solution.
D) Less acidic since the concentration of hydroxide ions will increase.
Answer: B
18.3 Acidic, Basic, and Neutral Solutions
1) Which of the following reactions illustrates an amphoteric compound?
+
A) 2 HF ⇌ H2F + FB) NaOH + HBr ⇌ NaBr + H2O
C) 2 H2 + O2 ⇌ 2 H2O
D) All are amphoteric.
E) none of the above
Answer: A
2) What do the brackets in the following equation represent?
+
-
[H3O ] × [OH ] = Kw
A) The brackets mean the molarity of the compound inside them.
B) The molecule inside does not react with the other molecules in brackets.
C) The molecule in brackets is undergoing hydrogen bonding with the other molecule in
brackets.
D) The first molecule in brackets is an acid and it reacts with the second molecule in brackets,
which is a base.
E) none of the above
Answer: A
+
-5
+
-8
3) What would the concentration of OH- be if the concentration of H3O was 1 × 10 M?
+
-
[H3O ] × [OH ] = Kw = 1 × 10
A) 1 × 10
B) 1 × 10
-14
-14
-5
9
C) 1 × 10
D) 1 × 10
E) 1 × 10
5
-9
Answer: E
-
4) What would the concentration of OH be if the concentration of H3O was 1 × 10 M?
+
-
[H3O ] × [OH ] = Kw = 1 × 10
-14
A) 1 × 10
B) 1 × 10
-14
-6
8
C) 1 × 10
D) 1 × 10
E) 1 × 10
6
-8
Answer: B
+
-11
5) What would the concentration of H3O be if the concentration of OH- was 1 × 10 M?
+
-
[H3O ] × [OH ] = Kw = 1 × 10
A) 1 × 10
-14
-3
3
B) 1 × 10
14
C) 1 × 10
D) 1 × 10
E) 1 × 10
12
-6
Answer: A
+
-
-1
6) What would the concentration of H3O be if the concentration of OH was 1 × 10 M?
+
[H3O ] × [OH-] = Kw = 1 × 10
A) 1 × 10
-3
B) 1 × 10
-2
C) 1 × 10
-4
D) 1 × 10
13
-14
E) none of the above
Answer: E
7) Qualitatively, what happens to the hydronium ion concentration if you increase the hydroxide
ion concentration?
+
A) The concentration of H3O stays the same but the ratio changes.
+
B) The concentration of H3O increases but the ratio stays the same.
+
C) The concentration of H3O increases to neutralize the excess hydroxide.
D) none of the above
Answer: D
8) Qualitatively, what happens to the hydroxide ion concentration if you decrease the hydronium
ion concentration?
-
-
+
A) The concentration of OH stays the same but the ratio OH /H3O changes.
-
B) The concentration of OH increases but the ratio stays the same.
-
C) The concentration of OH increases.
D) none of the above
Answer: C
9) Which of the following statements describes an acidic solution?
+
-
+
-
+
-
A) [H3O ] > [OH ]
B) [H3O ] [OH ]
B) [H3O ] [OH ]
B) [H3O ] < [OH ]
C) [H3O ] × [OH ] ≠ 1 × 10
+
-
+
-
D) [H3O ]/[OH ] = 1 × 10
E) [H3O ]/[OH ] = 1
Answer: E
-14
-14
12) Which of the above illustrations shows a basic aqueous solution?
A) A
B) B
C) C
D) All of the above are neutral solutions.
E) none of the above
Answer: A
13) Which of the above illustrations shows an acidic aqueous solution?
A) A
B) B
C) C
D) All of the above are neutral solutions.
E) none of the above
Answer: C
14) Which of the above illustrations shows a neutral aqueous solution?
A) A
B) B
C) C
D) All of the above are neutral solutions.
E) none of the above
Answer: B
15) As the hydronium ion concentration increases, the pH ________.
A) goes down
B) gets larger
C) starts to affect the OH- concentration
D) starts to alter the chemical properties of the water molecules
E) stays constant
Answer: A
16) If the pH of a solution is 10, what is the hydronium ion concentration?
A) 1 × 10
-10
M
10
B) 1 × 10 M
C) 10 M
D) -10 M
10
E) - 1 × 10 M
Answer: A
17) Which of the following solutions is the most acidic?
A) a solution with a pH = 14
B) a solution with a pH = 10
C) a solution with a pH = 7
D) a solution with a pH = 4
E) All of the solutions are basic.
Answer: D
18) Which of the following solutions is the most acidic?
A) a solution with a pH = 14
B) a solution with a pH = 12
C) a solution with a pH = 7
D) a solution with a pH = 13
E) All of the solutions are basic.
Answer: C
19) As the pH increases, the hydroxide ion concentration ________.
A) goes down
B) gets larger
+
C) starts to affect the H concentration
D) starts to decrease because it is reacting with the excess hydronium ions
E) stays constant
Answer: B
20) If the pH of a solution is 10, what is the hydroxide ion concentration?
-4
A) 1 × 10 M
B) 4 M
C) 14 M
D) -14 M
14
E) -1 × 10 M
Answer: A
21) If the pH of a solution was 7 and you were to increase the hydronium ion concentration
1000x, what would the pH be?
A) 4
B) 4 M
-4
C) 1 × 10 M
D) 7,000 M
E) 10
Answer: A
22) If the pH of a solution was 7 and you were to increase the hydroxide ion concentration 100x,
what would the pH be?
A) 9
B) 5 M
-5
C) 1 × 10 M
D) 700 M
E) 5
Answer: A
23) If you had a 1 M solution of a strong acid what would be its pH?
A) 0
B) 1
C) 7
D) 8
E) 13
Answer: A
24) If you had a 1 M solution of a weak acid what would be its pH?
A) 0
B) 6
C) 7
D) 8
E) 13
Answer: B
25) If you had a 1 M solution of a weak base what would be its pH?
A) 1
B) 6
C) 7
D) 8
E) 13
Answer: D
26) What does the value of Kw say about the extent to which water molecule react with
themselves?
A) Because the value of Kw is so small, the extent to which water ionizes is quite large.
B) Because the value of Kw is so small, the extent to which water ionizes is quite small.
C) Water molecules react with themselves at a constant rate, never increasing or decreasing.
D) When an acid is added to water, the value of Kw will decrease.
Answer: B
27) Why do we use the pH scale to indicate the acidity of a solution rather than simply stating
the concentration of hydronium ions?
A) It includes the concentration of hydronium and hydroxide ions.
B) It is used because the general public understands it.
C) It is more accurate to use the pH scale.
D) It is more convenient, since the concentration of hydronium ions is so small.
Answer: D
28) The amphoteric reaction between two water molecules is endothermic, which means that this
reaction requires the input of energy in order to proceed:
+
Energy + H2O + H2O → H3O + O H
-
The warmer the temperature of the water, the more thermal energy is available for this reaction,
and the more hydronium and hydroxide ions are formed. Based on this information, should the
value of Kw be expected to increase, decrease, or stay the same with increasing temperature?
A) The value of Kw will stay the same, since it is a constant.
B) The value of Kw will decrease, since there are more hydronium ions than hydroxide ions.
C) The value of Kw will increase since the rise in temperature allows for a higher concentration
of both ions.
D) The value of Kw will decrease since there are more hydroxide ions than hydronium ions.
Answer: C
29) Along with the pH scale, there is the pOH scale, which indicates the level of "basicity" in a
solution. Accordingly, pOH = -log[OH-]. What is the sum of the pH and the pOH of a solution
always equal to?
A) the negative of the product of the hydronium and hydroxide ions
B) the negative log of Kw, which is 14
C) The sum would equal 7, since that would be neutral for pH and pOH.
D) It is not constant because it depends on the acid/base solution in question.
Answer: B
30) When the hydronium ion concentration equals 1 mole per liter, what is the pH of the
solution? Is the solution acidic or basic?
A) pH = 0, this is an acidic solution.
B) pH = 1, this is an acidic solution.
C) pH = 10, this is a basic solution.
D) pH = 7, this is a neutral solution.
Answer: A
31) When the hydronium ion concentration equals 10 moles per liter, what is the pH of the
solution? Is the solution acidic or basic?
A) pH = 0, this is an acidic solution.
B) pH = 1, this is an acidic solution.
C) pH = -1, this is an acidic solution.
D) pH = 7, this is a neutral solution.
Answer: C
32) What would be the concentration of hydronium ions in a solution that had a pH = -3? Why
would such a solution be impossible to prepare?
+
A) Concentration of H3O = 3 M. It is impossible because it is hard to measure such a small
amount of hydronium ions accurately.
+
B) Concentration of H3O = 30 M. It is impossible because pH can not be negative.
+
30
C) Concentration of H3O = 10 M. It is impossible because any container used to hold the acid
would immediately corrode.
+
3
D) Concentration of H3O = 10 M. It is impossible because only so much acid can dissolve in
water before the solution becomes saturated.
Answer: D
33) What happens to the pH of an acidic solution as water is added?
A) The pH is not influenced by the addition of water.
B) The pH will decrease as the solution becomes more dilute.
C) The pH will increase as the solution becomes more dilute.
D) The pH will decrease since more hydronium ions are produced from the water.
Answer: C
34) What is the hydroxide ion concentration in an aqueous solution when the hydronium ion
concentration equals 1 × 10
-10
moles per liter?
A) The concentration of hydroxide ions is 1 × 10
-10
moles per liter.
-4
B) The concentration of hydroxide ions is 1 × 10 moles per liter.
-2
C) The concentration of hydroxide ions is 1 × 10 moles per liter.
-6
D) The concentration of hydroxide ions is 1 × 10 moles per liter.
Answer: B
35) When a hydronium ion concentration equals 1 × 10
solution? Is the solution acidic or basic?
A) The pH of this solution is 4, which is acidic.
B) The pH of this solution is 8, which is basic.
C) The pH of this solution is 6, which is acidic.
D) The pH of this solution is 10, which is basic.
-10
moles per liter, what is the pH of the
Answer: D
-4
36) When a hydronium ion concentration equals 1 × 10 moles per liter, what is the pH of the
solution? Is the solution acidic or basic?
A) The pH is of this solution is 4 and it is acidic.
B) The pH is of this solution is 8 and it is basic.
C) The pH is of this solution is 6 and it is acidic.
D) The pH is of this solution is 10 and it is basic.
Answer: A
37) What is the hydroxide ion concentration in an aqueous solution where the pH = 5?
A) The hydronium ion concentration equals 1 × 10
B) The hydronium ion concentration equals 1 × 10
C) The hydronium ion concentration equals 1 × 10
D) The hydronium ion concentration equals 1 ×10
-9
-7
-5
-3
Answer: C
18.4 Acidic Rain and Basic Oceans
1) What happens to the pH of soda water as it loses its carbonation?
A) It does not change since the carbonation has nothing to do with pH.
B) It decreases as it loses the carbon dioxide molecules which form the carbonic acid in the soda.
C) It increases as it loses the carbon dioxide molecules which form the carbonic acid in the soda.
D) It decreases as the soda becomes more concentrated through the loss of the carbon dioxide
gases.
Answer: C
2) Pour vinegar onto beach sand from the Caribbean and the result is a lot of froth and bubbles.
Pour vinegar onto beach sand from California, however, and nothing happens. Why?
A) Beaches in tropical climates generally have remnants of volcanic deposit not present in
California sand. These deposits contain soil with organic residue. Vinegar's acetic acid reacts
with organic matter.
B) The pH of the warm sands of tropical waters is well into the basic range, unlike the beach
sand in California. Therefore, the acidic vinegar reacts with Caribbean beach sand but not with
sand from California.
C) Beach sand from the Caribbean and many other tropical climates is made primarily of the
calcium carbonate remains of coral and shelled creatures. Vinegar is an acid and the calcium
carbonate is a base.
D) Caribbean beach sand contains deposits from the mouth of the Mississippi river which carries
with it a great deal of contamination from urban waste. These warm water contaminates react
with the acid in vinegar.
Answer: C
3) What would be the best explanation for the fact that most natural water has a pH of about 5.6?
A) Carbon dioxide reacts with water to form an acid.
B) Air contains acid rain particles.
C) Minerals that are dissolved in water are often acidic.
D) Many salts that dissolve in natural waters make the water basic.
E) none of the above
Answer: A
4) What is the source of acid rain?
A) Acid rain is from dissolved carbon dioxide.
B) All rain is acid rain because rain has a pH is less than 7.
C) Rain is normally basic, but depending on the weather it can get slightly acidic.
-7
D) All rain is acid rain because rain has a hydronium ion concentration greater than 10 M.
E) none of the above
Answer: E
5) Why might an area with a large amount of limestone (CaCO3) be less susceptible to acid rain?
A) The acid in the rain is neutralized by the natural base in the limestone.
B) The rain travels quickly through the porous limestone and therefore the rate of reaction is
slower.
C) Limestone is degraded by acid rain and therefore acid rain has the same damaging effects.
D) Only acid rain made from sulfur compounds reacts with the limestone.
E) none of the above
Answer: A
6) Why is carbon dioxide able to be stored more effectively in ocean water vs. fresh water?
A) The pH of the ocean is pretty high and so the carbon dioxide is trapped in a neutralization
reaction.
B) The oceans are large and so you can dissolve more CO2 in them.
C) Gases are more soluble in cold water than warm water and the oceans are colder than fresh
water lakes so you can dissolve more CO2 in them.
D) The pH of the ocean is very low and so the carbon dioxide is trapped as an acid because like
dissolves like.
E) none of the above
Answer: A
7) Why might a small piece of chalk made of calcium carbonate be useful for alleviating acid
indigestion?
A) Calcium carbonate is a base that reacts to neutralize any excess acids.
B) Calcium carbonate is able to absorb excess acid and carry it out of the system.
C) Calcium carbonate is able to add an extra lining to the stomach to protect it from the excess
acid.
D) Calcium carbonate is able to turn the acid into a gas which can relieve the build up of excess
acid.
Answer: A
8) How might you tell whether or not your toothpaste contained either calcium carbonate, CaC
O3, or baking soda, NaHCO3, without looking at the ingredients label?
A) if the toothpaste bubbles when heated
B) if the toothpaste bubbles when added to ammonia, such as window cleaner
C) if the toothpaste produces a salt (NaCl) when added to HCl
D) if the toothpaste bubbles when added to vinegar
Answer: D
9) Lakes lying in granite basins, such as those in the northeastern U.S., tend to become acidified
by acid rain more readily than lakes lying in limestone basins, such as those found in the
midwestern U.S. Why is this so?
A) The granite contains acidic minerals that dissolve in the rain water and are added to the lakes.
B) Since the acidified water cannot percolate through the granite, the acid in the lakes becomes
more concentrated.
C) The limestone, which is calcium carbonate, serves to neutralize the acid in the rain.
D) There is more acid rain in the northeast than in the midwestern regions of the U.S.
Answer: C
10) Cutting back on the pollutants that cause acid rain is one solution to the problem of acidified
lakes. Suggest another.
A) stop using NaCl to salt the roads in the winter
B) add a neutralizing substance such as limestone
C) add ammonium ions to the lakes
D) add chlorine and filter the water to remove any acidity in the lake
Answer: B
18.5 Losing and Gaining Electrons
1) What is oxidation?
A) the loss of electrons
B) the reaction with oxygen
C) the reduction of oxygen
D) the gaining of electrons
E) the addition of an electron to the valence shell
Answer: A
2) What is a reduction?
A) the gain of electrons
B) the reduction of the number of electrons
C) the loss of an electron from the valence shell
D) the reaction of oxygen with a reductant
E) the formation of red compounds in the presence of an oxidant
Answer: A
3) Which of the following statements is untrue about oxidation and reduction processes?
A) An oxidation can happen without a reduction.
B) It involves the exchange of electrons.
C) Often ions are generated or consumed.
D) Electrons are often involved in oxidation and reduction reactions.
E) All of the above are true.
Answer: A
4) Which of the following statements about oxidation and reduction reactions is true?
A) More than one electron can be transferred in an oxidation and reduction reaction.
B) In a half-reaction, only half of an electron is transferred.
C) Only neutral atoms are formed in oxidation and reduction reactions.
D) A half-reaction is only used for reduction reactions.
E) None of the above are true.
Answer: A
5) How many electrons are gained or lost in the following half-reaction?
+
Na → Na
A) 1 electron is lost
B) 1/2 electron is gained
C) 1/2 electron is lost
D) 1 electron is gained
E) 2 electrons are gained
Answer: A
6) How many electrons are gained or lost in the following half-reaction?
2 Na → 2 Na
+
A) 2 electrons are lost
B) 1/2 electron is gained
C) 1/2 electron is lost
D) 2 electrons are gained
E) 4 electrons are gained
Answer: A
7) How many electrons are gained or lost in the following half-reaction?
Cl2 → 2 Cl
-
A) 2 electrons are lost
B) 1/2 electron is gained
C) 1/2 electron is lost
D) 2 electrons are gained
E) 4 electrons are gained
Answer: D
8) How many electrons are gained or lost in the following half-reaction?
Zn → Zn
+2
A) 2 electrons are lost
B) 1/2 electron is gained
C) 1/2 electron is lost
D) 2 electrons are gained
E) 4 electrons are gained
Answer: A
9) Which of the half-reactions below would be complementary, balance the following halfreaction, and be chemically reasonable?
Br2 → 2 Br
-
A) 2 K → 2 K
+
+
B) K → K
+
C) K → K
+
D) 2 K → 2 K
E) K → K
+2
Answer: A
10) Which of the half-reactions below would be complementary and balance the following halfreaction?
+2
Zn → Zn
A) Cu → Cu
+2
+
B) K → K
C) 2 Cu → 2 Cu
+2
+
D) 2 K → 2 K
E) Cl2 → 2 Cl
-
Answer: A
11) Which of the following species is undergoing oxidation?
2 CuBr → 2Cu + Br2
A) Cu
B) CuBr
C) Cu
D) Br
+
-
E) Br2
Answer: D
12) Which of the following species is undergoing reduction?
2 CuBr → 2Cu + Br2
A) Cu
B) CuBr
C) Cu
D) Br
+
-
E) Br2
Answer: C
13) Which of the following species is the oxidizing agent?
2 CuBr → 2Cu + Br2
A) Cu
B) CuBr
C) Cu
D) Br
+
-
E) Br2
Answer: C
14) Which of the following species is the reducing agent?
2 CuBr → 2Cu + Br2
A) Cu
B) CuBr
C) Cu
D) Br
+
-
E) Br2
Answer: D
15) Which of the following materials is most likely to undergo oxidation?
A) Na
+
B) Na
C) Cl2
D) Cl
-
E) both A and B
Answer: A
16) Which of the following materials is most likely to act as an oxidizing agent?
A) Na
+
B) Na
C) Cl2
D) Cl
-
E) both A and B
Answer: C
17) Which of the following materials is most likely to undergo reduction?
A) Na
+
B) Na
C) Cl2
D) Cl
-
E) both A and B
Answer: C
18) Which of the following materials is most likely to act as a reducing agent?
A) Na
+
B) Na
C) Cl2
D) Cl
-
E) both A and B
Answer: A
19) What might the relationship be between an element's electronegativity and its ability to
behave as an oxidizing agent?
A) As the electronegativity goes up the ability of an element to act as an oxidant increases.
B) As the electronegativity goes up the ability of an element to act as an oxidant decreases.
C) As the electronegativity goes up the ability of an element to act as an oxidant stays the same.
D) As the electronegativity increases the element has a tendency to undergo oxidation.
E) none of the above
Answer: A
20) What element is oxidized in the following equation and what element is reduced?
2+
+
Sn + 2 Ag → Sn + 2 Ag
2+
A) The tin ion, Sn , is oxidized, while the silver, Ag, is reduced.
2+
B) The tin ion, Sn , is reduced, while the silver, Ag, is oxidized.
2+
C) Both the tin ion, Sn , and the silver, Ag, are reduced.
2+
D) Both the tin ion, Sn , and the silver, Ag, are oxidized.
Answer: B
21) What element is behaves as the oxidizing agent in the following equation and what element
behaves as the reducing agent?
2+
+
Sn + 2 Ag → Sn + 2 Ag
2+
A) The tin ion, Sn , is the oxidizing agent while silver, Ag, is the reducing agent.
2+
B) The tin ion, Sn , is the reducing agent while silver, Ag, is the oxidizing agent.
+
C) The tin, Sn, is the reducing agent while silver ion, Ag , is the oxidizing agent.
+
D) The tin, Sn, is the oxidizing agent while silver ion,Ag , is the reducing agent.
Answer: A
22) Hydrogen sulfide, H2S, burns in the presence of oxygen, O2, to produce water, H2O, and
sulfur dioxide, SO2. Through this reaction, is sulfur oxidized or reduced?
2 H2S + 3 O2 → 2 H2O + 2 SO2
A) Sulfur is reduced.
B) Sulfur is oxidized
C) Sulfur is both oxidized and reduced.
D) Sulfur is neither oxidized nor reduced.
Answer: B
23) For each of the following unbalanced equations, which is depicted: oxidation or reduction?
3+
a) Cr → Cr b) Sn → Sn(OH)4
2
A) a) oxidation; b) reduction
B) a) reduction; b) oxidation
C) a) reduction; b) reduction
D) a) oxidation; b) oxidation
Answer: D
24) In the above diagram, which atom is oxidized, the darker colored atom or the lighter colored
atom?
A) Both of the atoms are oxidized.
B) Neither of the atoms is oxidized.
C) Only the darker colored atom is oxidized.
D) Only the lighter colored atom is oxidized.
Answer: C
25) In the above diagram, which atom behaves as the oxidizing agent, the lighter colored atom or
the darker colored atom?
A) Both atoms behave as the oxidizing agent.
B) Neither of the atoms behave as the oxidizing agent.
C) The darker colored atom behaves as the oxidizing agent.
D) The lighter colored atom behaves as the oxidizing agent.
Answer: D
26) How does an atom's electronegativity relate to its ability to become oxidized?
A) The greater the electronegativity of an atom, the greater its ability to become oxidized.
B) The lower the electronegativity of an atom, the lower its ability to become oxidized.
C) The greater the electronegativity of an atom, the lower its ability to become oxidized.
D) Electronegativity does not effect the atom's ability to become oxidized.
Answer: C
27) The general chemical equation for photosynthesis is shown below. Through this reaction is
the carbon oxidized or reduced? How can you tell?
6 CO2 + 6 H2O → C6H12O6 + 6 O2
A) Oxidized, since carbon is in the +4 oxidation state in CO2 but in the +6 oxidation state in the
product, C6H12O6, glucose.
B) Reduced, since in carbon dioxide there are two oxygen atoms for every one carbon but within
the product, C6H12O6, (glucose), there is only one oxygen for every one carbon.
C) Neither, since carbon does not change its oxidation state and is neither oxidized nor reduced.
D) Both, since the carbon atoms within the glucose molecules display two different charge states.
Answer: B
28) The general chemical equation for photosynthesis is shown below. Through this reaction are
the oxygens of the water molecules, H2O, oxidized or reduced?
6 CO2 + 6 H2O → C6H12O6 + 6 O2
A) The oxygens of the water molecules are oxidized.
B) The oxygens of the water molecules are reduced.
C) The oxygens of some of these water molecules are oxidized while others are reduced.
D) The oxygens of the water molecules are neither oxidized nor reduced.
Answer: A
29) Chemical equations need to be balanced not only in terms of the number of atoms, but also
by the charge. In other words, just as there should be the same number of atoms before and after
the arrow of an equation, there should be the same charge. What set of coefficients is necessary
to balance the following chemical equation?
2+
____ Sn + ____ Ag → ____ Sn + ____ Ag
+
A) 1, 2, 1, 2
B) 1, 1, 1, 2
C) 1, 2, 2, 2
D) 1, 1, 2, 1
Answer: A
30) Chemical equations need to be balanced not only in terms of the number of atoms, but also
by the charge. In other words, just as there should be the same number of atoms before and after
the arrow of an equation, there should be the same charge. What set of coefficients is necessary
to balance the following chemical equation?
4+
+
3+
____ Ce + ____ Cl → ____ Ce + ____ Cl2
A) 1, 2, 1, 1
B) 2, 2, 2, 1
C) 1, 4, 1, 2
D) 3, 4, 3, 2
Answer: B
31) Which element is closer to the upper right corner of the periodic table, the one indicated by
the lighter colored atoms or the darker colored atoms?
A) the element indicated by the darker color
B) the element indicated by the lighter color
C) More information is needed in order to determine which element is closer to the upper right of
the periodic table.
D) Both the lighter and darker colored elements are likely found at the upper right corner of the
periodic table.
Answer: A
32) Clorox is a laundry bleaching agent used to remove stains from white clothes. Suggest why
the name begins with Clor- and ends with -ox.
A) Clor because it has chlorine, ox because it is as strong as an ox.
B) The active ingredient contains chlorine atoms, which behave as strong oxidizing agents.
C) Chlor because it has chlorine ions, ox because it is reduced.
D) Chlor because it has chlorine ions, ox because it uses oxygen.
Answer: B
33) When lightning strikes, nitrogen molecules, N2, and oxygen molecules, O2, in the air react to
-
form nitrates, NO3 , which come down in the rain to help fertilize the soil. Is this this an example
of oxidation or reduction?
A) The formation of nitrates is an example of oxidation.
B) The formation of nitrates is an example of reduction.
C) Both. The nitrogen is oxidized as it reacts with the oxygen while the oxygen is reduced.
D) Neither. Although the bonds of both the N2 and O2 molecules are broken to form the NO3-,
neither oxidation nor reduction occurs.
Answer: C
34) Glucose, C6H12O6, is a simple sugar that the body metabolizes into two molecules of pyruvic
acid, C3H4O3. Is the glucose oxidized or reduced as it transforms into pyruvic acid?
A) The glucose is oxidized.
B) The glucose is reduced.
C) Parts of the glucose molecule are oxidized while others are reduced.
D) Glucose is neither oxidized or reduced as it transforms into pyruvic acid.
Answer: A
35) Upon ingestion, grain alcohol, C2H6O, is metabolized into acetaldehyde, C2H4O, which is a
toxic substance causing headaches as well as joint pains typical of a "hangover." Is the grain
alcohol oxidized or reduced as it transforms into acetaldehyde?
A) The grain alcohol is reduced.
B) The grain alcohol is oxidized.
C) Some of the grain alcohol is oxidized and some is reduced to other products.
D) The grain alcohol is neither oxidized nor reduced.
Answer: B
18.6 Harnessing the Energy of Flowing Electrons
1) Which of the following statements about electrochemistry is not true?
A) It is the study of how electrical energy and chemical reactions are related.
B) It involves the use of a set of oxidation-reduction reactions to produce electrical current.
C) It involves the use of electrical current to produce an oxidation-reduction reaction.
D) It is the study of how electrons are transferred from one chemical compound to another.
E) All of the above are true.
Answer: E
2) The following set of redox reactions takes place when iron is dipped in a solution of copper
ions.
+2
Fe → Fe + 2e+2
Cu + 2e- → Cu
Which of the following describes what is happening on the surface of the iron?
A) The copper starts to plate out on iron.
B) The iron rusts in the water.
C) The iron starts to plate out on the copper.
D) The iron corrodes the copper.
E) none of the above
Answer: A
3) The following set of redox reactions takes place when iron is dipped into a solution of copper
ions.
+2
Fe → Fe + 2e+2
Cu + 2e- → Cu
Which of the following describes what is happening with the electrons in the solution?
A) The iron metal is releasing electrons and they are traveling to the copper ions.
B) The copper is releasing electrons and they are traveling to the iron ions.
C) The iron ions are gaining electrons from the copper metal.
D) The copper ions are releasing electrons and they are traveling to the iron metal.
E) none of the above
Answer: A
4) The following set of redox reactions takes place as shown.
If you had two containers filled with the ion solution described above with only a wire
connecting a piece of iron (in container A) and a piece of copper (in container B), describe what
happens.
A) A little bit of iron is converted into iron ions and a little bit of copper ion is converted into
copper metal.
B) All of the iron is transformed into iron ions and all of the copper is transformed into copper
ions.
C) All of the iron is transformed into iron ions and all of the copper ions are transformed into
copper metal.
D) All of the iron ions are transformed into iron metal and all of the copper is transformed into
copper ions.
E) All of the iron ions are transformed into iron metal and all of the copper is transformed into
copper metal.
Answer: A
5) The following set of redox reactions takes place as shown.
If you had two containers filled with the ion solution described above with only a wire
connecting a piece of iron (in container A) and a piece of copper (in container B), which way do
the electrons flow?
A) There is no continuous flow of electrons.
B) The electrons from from container A to container B.
C) The electrons flow from container B to container A.
D) The electrons flow back and forth between the two containers.
E) The electrons only move in the containers they originate in.
Answer: A
6) What is the purpose of a salt-bridge?
A) to allow ions to migrate between solutions
B) to allow people to cross over salt water
C) to allow electrons to migrate through solutions
D) to allow salt to form in the oxidation-reduction reactions
E) none of the above
Answer: A
7) The following set of redox reactions takes place as shown.
If you had two containers filled with the ion solution described above with a wire connecting a
piece of iron (in container A) and a piece of copper (in container B) and a salt-bridge connecting
the two containers, describe what happens.
A) A little bit of iron is converted into iron ions and a little bit of copper ion is converted into
copper metal.
B) All of the iron is transformed into iron ions and all of the copper is transformed into copper
ions.
C) All of the iron is transformed into iron ions and all of the copper ions are transformed into
copper metal.
D) All of the iron ions are transformed into iron metal and all of the copper is transformed into
copper ions.
E) All of the iron ions are transformed into iron metal and all of the copper is transformed into
copper metal.
Answer: C
8) The following set of redox reactions takes place as shown.
If you had two containers filled with the ion solution described above with a wire connecting a
piece of iron (in container A) and a piece of copper (in container B) and a salt-bridge connecting
the two containers, which way do the electrons flow?
A) There is no continuous flow of electrons.
B) The electrons flow from container A to container B.
C) The electrons flow from container B to container A.
D) The electrons flow back and forth between the two containers.
E) The electrons only move in the containers they originate in.
Answer: B
9) The following set of redox reactions takes place as shown.
If you had two containers filled with the ion solution described above with a wire connecting a
piece of iron (in container A) and a piece of copper (in container B) and a salt-bridge connecting
the two containers, which way do the positive ions in the salt-bridge flow?
A) There is no flow of positive ions in the salt-bridge
B) The positive ions flow from container A to container B.
C) The positive ions flow from container B to container A.
D) The positive ions flow back and forth between the two containers.
E) The ions only move in the containers they originate in.
Answer: B
10) Which of the following describes an electrode?
A) Any material that conducts electrons into a media where electrochemical reactions are taking
place.
B) Any material that conducts electrons out of a media where electrochemical reactions are
taking place.
C) Any material that conducts electrons.
D) Any material that is undergoing an oxidation-reduction reaction in a battery.
E) either A or B
Answer: E
11) Which of the following statements best describes a cathode?
A) the negatively charged electrode of a battery or electrochemical apparatus
B) the place where oxidation is taking place in a battery or electrochemical apparatus
C) the place from which electrons are flowing away from
D) all of the above
E) none of the above
Answer: E
12) Which of the following statements best describes an anode?
A) the negatively charged electrode of a battery or electrochemical apparatus
B) the place where oxidation is taking place in a battery or electrochemical apparatus
C) the place from which electrons are flowing away from
D) all of the above
E) none of the above
Answer: D
13) What is the purpose of the salt bridge in a voltaic cell?
A) to prevent any further migration of electrons through the wire
B) to allow for the build up of positively charged ions in one container and negatively charged
ions in the other container
2+
2+
C) to allow the Fe and the Cu to flow freely between the two containers
D) to allow for a balance of charge between the two chambers
Answer: D
2+
2+
14) In the oxidation-reduction reaction Mg(s) + Cu (aq) → 3 Mg (aq) + Cu(s), which atom or
ion is reduced? Which atom or ion is oxidized?
2+
A) The Cu ion is oxidized as it gains electrons from the copper metal, Cu. The magnesium
metal, Mg, is reduced as it loses electrons to form Mg
2+.
2+
2+
B) The Mg ion is reduced as it gains electrons from the copper metal, Cu. The Cu is oxidized
as it loses electrons to the Mg
2+.
2+
C) The Cu ion is reduced as it gains electrons to form copper metal, Cu. The magnesium metal,
Mg, is oxidized as it loses electrons to form Mg
2+.
D) Since Mg goes from a solid to an aqueous solution and Cu goes from an aqueous solution to a
solid, an oxidation-reduction reaction did not occur.
Answer: C
15) In a battery, the following two oxidation-reduction reactions are taking place:
+2
rxn A: Zn → Zn + 2e-
rxn B: 2 NH4+ + 2e- → 2 NH3 + H2
Which reaction is taking place at the anode?
A) rxn A
B) rxn B
C) Both reactions are happening at both the anode and cathode.
D) Both reactions are happening at the electrode.
E) The reaction takes place at the electrode, not the anode.
Answer: A
16) In a battery, the following two oxidation-reduction reactions are taking place:
+2
rxn A: Zn → Zn + 2e+
rxn B: 2 NH4 + 2e- → 2 NH3 + H2
Which reaction is taking place at the cathode?
A) rxn A
B) rxn B
C) Both reactions are happening at both the anode and cathode.
D) Both reactions are happening are happening at the electrode.
E) The reaction takes place at the electrode, not the cathode.
Answer: B
17) In a battery, the following two oxidation-reduction reactions are taking place:
rxn A: Zn + 2 OH- → ZnO + H2O + 2erxn B: 2 MnO2 + H2O + 2e- → Mn2O3 + 2 OHWhat is undergoing oxidation?
A) Zn
B) ZnO
C) MnO2
D) H2O
E) OH
-
Answer: A
18) In a battery, the following two oxidation-reduction reactions are taking place:
rxn A: Zn + 2 OH- → ZnO + H2O + 2erxn B: 2 MnO2 + H2O + 2e- → Mn2O3 + 2 OHWhat is undergoing reduction?
A) Zn
B) ZnO
C) MnO2
D) H2O
E) OH
-
Answer: C
19) In a battery, the following oxidation-reduction reaction is taking place:
Mn2O3 + ZnO → 2 MnO2 + Zn
What is undergoing reduction as written?
A) Zn
B) ZnO
C) MnO2
D) Mn2O3
E) none of the above
Answer: B
20) In a battery, the following oxidation-reduction reactions are taking place:
Mn2O3 + ZnO → 2 MnO2 + Zn
What is undergoing an oxidation as written?
A) Zn
B) ZnO
C) MnO2
D) Mn2O3
E) none of the above
Answer: D
21) In a battery, the following oxidation-reduction reactions are taking place:
Mn2O3 + ZnO → 2 MnO2 + Zn
What is being formed at the cathode?
A) Zn
B) ZnO
C) MnO2
D) Mn2O3
E) none of the above
Answer: A
22) In a battery, the following oxidation-reduction reactions are taking place:
Mn2O3 + ZnO → 2 MnO2 + Zn
What is being formed at the anode?
A) Zn
B) ZnO
C) MnO2
D) Mn2O3
E) none of the above
Answer: C
23) In a battery, if the following oxidation-reduction reactions takes place normally:
Mn2O3 + ZnO → 2 MnO2 + Zn
What reaction would be taking place if you were charging the battery?
A) 2 MnO2 + Zn → Mn2O3 + ZnO
B) ZnO → Zn
C) Mn2O3 → MnO2
D) all of the above
E) none of the above
Answer: A
24) Why might disposing of a lead-acid battery, nickel-cadmium battery or mercury battery in a
landfill be a bad thing?
A) Cadmium, mercury, and lead are all toxic metals and could leak out of the landfill.
B) Cadmium, mercury, and lead are all very reactive and generate highly unstable compounds.
C) Cadmium, mercury, and lead are all radioactive and release radiation.
D) all of the above
E) none of the above
Answer: A
25) Your car lights were left on while you were shopping, and now your car battery is dead. Has
the pH of the battery fluid increased or decreased?
A) The pH of the battery fluid has increased.
B) The pH of the battery fluid has decreased.
C) The pH of the battery fluid does not change.
D) Since the lights were left on and the battery is dead, the pH of the battery fluid must be zero.
Answer: A
26) Why does a battery that has thick zinc walls last longer than one that has thin zinc walls?
A) Thick zinc walls prevent the battery from over heating.
B) Thicker zinc walls prevent electrons from being lost into the surrounding environment.
C) Thicker zinc walls last longer at holding in the battery acid.
D) The zinc walls are transformed into zinc ions as the battery provides electricity.
Answer: D
27) What is the primary difference between a fuel cell and a battery?
A) Fuel cells do not run down because they can be refueled; batteries run down and need to be
recharged.
B) Batteries can be recharged, fuel cells cannot.
C) Batteries supply electricity; fuel cells supply heat.
D) Fuel cells oxidize to supply electricity, batteries reduce to supply electricity.
E) Fuel cells do not use metals as oxidants and reductants, batteries have a static reservoir of
oxidant and reductant.
Answer: A
28) In one type of fuel cell the following oxidation-reduction reactions are taking place:
2 H2 + O2 → 2 H2O
What is the fuel?
A) H2
B) O2
C) H2O
D) all of the above
E) none of the above
Answer: A
29) In one type of fuel cell, the following oxidation-reduction reactions are taking place:
2 H2 + O2 → 2 H2O
What is the oxidant?
A) H2
B) O2
C) H2O
D) all of the above
E) none of the above
Answer: B
30) What is one of the advantages of a fuel cell?
A) They can run for a very long time as long as you keep adding fuel.
B) They are more efficient than combustion.
C) They have lower emission of pollutants than combustion.
D) all of the above
E) only A and B
Answer: D
31) What is one of the drawbacks to using fuel cells?
A) The fuel of the fuel cells is hard to handle.
B) They are less efficient than combustion energy sources or batteries.
C) They are very big and bulky, which makes them hard to use in small devices.
D) There are no drawbacks.
E) only A and B
Answer: A
32) Why don't the electrodes of a fuel cell deteriorate the way the electrodes of a battery do?
A) As long as fuel is supplied, fuel cells don't run down, but car batteries die when the electronproducing chemicals are consumed.
B) Fuel cell electrodes are made of graphite, which does not deteriorate.
C) Fuel cell electrodes are self-replenishing thanks to the KOH-containing paste.
D) Fuel cell do not use electrodes, so there are none to deteriorate.
Answer: A
18.7 Electrolysis
1) How is electrolysis different from what is going on chemically inside a battery?
A) They are the same process, just reversed.
B) Electrolysis does not use electrons.
C) Electrolysis only uses electrons from a cathode.
D) You cannot make pure compounds with electrolysis.
E) You do not produce a chemical change in electrolysis.
Answer: A
2) For the following electrolysis reaction:
-2
2 AlOF3 + C → 2 Al + CO2 + FWhere would the aluminum form?
A) cathode
B) anode
C) in solution
D) Aluminum formation does not happen because electrons do not flow in above reaction.
E) none of the above
Answer: A
3) Why is recycling of aluminum better for the environment than electrolysis of bauxite (an
aluminum ore)?
A) It takes less energy to recycle aluminum.
B) Electrolysis releases harmful gases into the atmosphere.
C) The bauxite is extremely rare and there is very little aluminum in the world.
D) Electricity is extremely cheap and it is better to use cheap electricity.
E) none of the above
Answer: A
4) A major source of chlorine gas, Cl2, is from the electrolysis of brine, which is concentrated
salt water, NaCl (aq). Which of the following is the balanced chemical reaction for this
electrolysis reaction?
A) NaCl (aq) + H2O → NaOH (aq) + Cl2 (g) + H2 (g)
B) 2 NaCl (aq) + H2O → Na2O (aq) + 2 HCl (aq)
C) 2 NaCl (aq) + 2 H2O → 2 Na (s) + O2 (g) + 2 H2 (g) + Cl2 (g)
-
D) 2 NaCl (aq) + H2O → 2 NaH (aq) + Cl2O (aq)
Answer: A
5) A major source of chlorine gas, Cl2, is from the electrolysis of brine, which is concentrated
salt water, NaCl (aq). What is the sign of the electrode where the chlorine gas is formed? Is it
negative or positive?
A) Positive, since the chloride ions lose electrons to form chlorine molecules.
B) Negative, since the chlorine gas needs to deposit electrons to form chloride ions.
C) Neither, since chlorine gas is a neutral molecule, there is not electrode attraction.
D) Both, since the chloride ions from NaCl (aq) are attracted to the positive electrode to form
chlorine molecules while the produced chlorine gas molecules move to deposit electrons at the
negative electrode.
Answer: A
6) Sodium metal is
A) oxidized in the production of aluminum.
B) reduced in the production of aluminum.
C) both oxidized and reduced in the production of aluminum.
D) neither oxidized nor reduced in the production of aluminum.
Answer: A
7) Jewelry is often manufactured by electroplating an expensive metal such as gold over a
cheaper metal. A setup for this process can be sketched as follows:
What would happen if the battery connections were suddenly reversed?
A) The ring would continue to electroplate with gold.
B) Gold ions in solution would get reduced and settle to the bottom of the container.
C) Gold ions in solution would begin to electroplate onto the gold electrode.
D) All electrolysis would stop.
Answer: C
8) How might electrolysis be used to raise the hull of a sunken ship?
A) An electric current passed through the hull of the ship would produce electrolysis and the
gases trapped in the compartments of the vessel would push it upwards.
B) The electrolysis of the water beneath the hull of the ship would boil the water and create
upward pressure, thus buoying the ship upward.
C) The gaseous products of the electrolysis of water could be collected with large bags attached
to the hull of the ship. As the bags inflate with the gas they are buoyed upward pulling the ship
also upward.
D) Electrolysis could only be used to raise the hull of a ship if the ship were made of iron. If so,
the electrolysis of the iron metal might produce enough gas to lift the ship.
Answer: C
18.8 Corrosion and Combustion
1) Why is oxygen usually an oxidizing agent?
A) It is a very electronegative element.
B) It does not undergo reduction.
C) It likes to be oxidized.
D) It is very abundant and so it is easier to react than nitrogen.
E) all of the above
Answer: A
2) Rust has a tendency to form when iron in contact with water reacts according to the following
reaction:
4 Fe + 3 O2 → 2 Fe2O3
What is happening at the cathodic region?
A) Iron is being oxidized.
B) Oxygen is being oxidized.
C) Oxygen is being reduced
D) Iron is being reduced.
E) none of the above
Answer: C
3) Rust has a tendency to form when iron in contact with water reacts according to the following
reaction:
4 Fe + 3 O2 → 2 Fe2O3
What is happening at the anodic region?
A) Iron is being oxidized.
B) Oxygen is being oxidized.
C) Oxygen is being reduced.
D) Iron is being reduced.
E) none of the above
Answer: A
4) Aluminum metal undergoes the same basic corrosion process that iron does yet it does not
decompose as rapidly. Why?
A) The aluminum oxide does not flake off like rust and acts as a protective layer.
B) Aluminum is harder to oxidize than iron.
C) Aluminum is harder to reduce than iron.
D) The aluminum oxide product undergoes a reduction to produce aluminum metal.
E) The aluminum is galvanized, which prevents oxidation.
Answer: A
5) How does connecting a metal like iron with a wire to a metal that is easier to oxidize like zinc
help prevent corrosion of the iron?
A) The other metal is oxidized instead and the electrons travel to the iron, keeping it from
oxidizing.
B) The other metal absorbs the electrons from the iron, which keeps the iron from undergoing
oxidation.
C) The wire is acting as an oxidant and keeps the two metals from undergoing other chemical
reactions.
D) There is no salt-bridge, so there is no reaction between the two metals.
E) The other metal is oxidized and adsorbs all the oxidant, keeping it away from the iron.
Answer: A
6) How would connecting iron with a wire to a piece of metal like copper, which undergoes
reduction very easily, affect the rate at which the iron corrodes?
A) It would increase the rate of corrosion.
B) It would decrease the rate of corrosion.
C) The rate would stay the same.
D) Rates are only affected by temperature.
E) none of the above
Answer: A
2+
7) Why is the formation of iron hydroxide, Fe(OH)2, from Fe and OH- not considered an
oxidation-reduction reaction?
A) The iron is only oxidized and nothing is reduced.
B) The iron is only reduced, not oxidized.
2+
C) The Fe ion is not changed during this chemical reaction.
D) Iron can never be oxidized or reduced.
Answer: C
8) A chemical equation for the combustion of propane, C3H8, is shown below. Through this
reaction is the carbon oxidized or reduced?
C3H8 + 5O2 → 3 CO2 + 4 H2O
A) The carbon is oxidized.
B) The carbon is reduced.
C) Some of the carbons are oxidized while others are reduced.
D) The carbon is neither oxidized nor reduced.
Answer: A
9) The oxidation of iron to rust is a problem structural engineers need to be concerned about, but
the oxidation of aluminum to aluminum oxide is not so much of a problem. Why?
A) Since aluminum is so light and inexpensive, it is easily replaced when corroded.
B) Aluminum oxide is insoluble in water and thus forms a protective coating that prevents
continued oxidation of the aluminum.
C) Aluminum oxide is even stronger than aluminum.
D) The oxidation of aluminum is a very slow reaction, taking hundreds of years before any
structural changes are noticed.
Answer: B
10) How many electrons are transferred from iron atoms to oxygen atoms in the formation of two
molecules of iron hydroxide, Fe(OH)2?
A) 4 electrons
B) 8 electrons
C) 16 electrons
D) 12 electrons
Answer: A
11) Why are combustion reactions generally exothermic?
A) Hydrogen easily pulls electrons from the oxygen in water molecules and are reduced.
B) During combustion oxygen is oxidized, which gives off lots of energy.
C) Combustion involves the transfer of electrons to oxygen, which has an extremely high
tendency for gaining electrons.
D) It is highly exothermic because combustion involves an oxidation-reduction reaction between
a metallic material and oxygen.
Answer: C
12) Water is 88.88 percent oxygen by mass. Oxygen is exactly what a fire needs to grow brighter
and stronger. So why doesn't a fire grow brighter and stronger when water is added to it?
A) Oxygen in water is already "reduced" from the hydrogen atoms, so this oxygen atom no
longer has a great attraction for additional electrons.
B) The oxygen is chemically bound to hydrogen atoms.
C) Oxygen in water is completely different from oxygen O2, which is what is required for
combustion.
D) all of the above
Answer: D
13) Iron atoms have a greater tendency to oxidize than do copper atoms. Is this good news or bad
news for a home in which much of the plumbing consists of iron and copper pipes connected
together? Explain.
A) This is bad news, since the iron atoms will be reduced by the copper atoms.
B) This is not a problem, since the strength of the copper will make up for the weakness of the
iron.
C) It is bad news. The iron atoms will lose electrons to the copper atoms, which will pass those
electrons onto oxygen atoms that are in contact with the surface.
D) This is not a problem since any electrons lost will be replaced by copper electrons.
Answer: C
14) Copper atoms have a greater tendency to be reduced than iron atoms do. Was this good news
or bad news for the Statue of Liberty, whose copper exterior was originally held together by steel
rivets?
A) This was good news since the steel rivets prevented the copper from eroding.
B) Electrons will preferentially flow from the iron to the copper and then onto oxygen. Corrosion
is thus accelerated around the interface of these two metals.
C) This combination of metals have no effect on each other and that is why engineers chose to
use them together.
D) This combination of metals caused the copper to oxidize and turn green.
Answer: B
15) One of the products of combustion is water. Why doesn't this water extinguish the
combustion?
A) While areas of combustion are being extinguished, new areas are combusting.
B) Combustion only produces micro amounts of water.
C) The chemical combustion reaction is happening too fast for the water to have an effect on the
fire.
D) This water is in the gaseous phase and merely floats away from the fire.
Answer: D
16) Why is the air over an open flame always moist?
A) The hot flame vaporizes the water in the air above the flame.
B) One of the products of combustion is water vapor.
C) Warm air contains more humidity than cold air.
D) None of the above is true.
Answer: B
17) Upon combustion, about how many grams of water vapor are produced from every 16 grams
of methane, CH4?
CH4 + 2 O2 → CO2 + 2 H2O
A) 16 grams
B) 18 grams
C) 36 grams
D) 8 grams
Answer: C
Test Bank for Conceptual Physical Science
Paul Hewitt, John Suchocki, Leslie Hewitt
9780321752932, 9780134060491
