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The Molecules of Cells
Multiple Choice Questions
1. If an element has an atomic number of 12, how many electrons are in its outermost shell?
A. 1
B. 10
C. 8
D. 2
E. 12
Two electrons fill the innermost shell and eight fill the next, leaving two for the outermost
shell.
Bloom’s Level: 3. Apply
Learning Outcome: 02.01.01 Describe how protons, neutrons, and electrons relate to atomic
structure.
Section: 02.01
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-2
2. If an element has an atomic number of 15, then
A. the atomic mass must also be 15.
B. the atom has 15 electrons.
C. there are 7 electrons in the outermost shell.
D. the atom has 15 neutrons.
E. the atom must have only one orbital.
In an electrically neutral atom, the number of protons (the atomic number) is the same as the
number of electrons. The atom would need three orbitals to accommodate 15 electrons, and
there would be 5 electrons in its outermost shell. The atomic mass includes the protons and
the neutrons; the number of neutrons is not specified in this question.
Bloom’s Level: 3. Apply
Learning Outcome: 02.01.02 Use the periodic table to determine relationships among atomic
number and mass number.
Section: 02.01
Topic: Chemistry
3. The chemical reactivity of an element is dependent on
A. the number of protons.
B. the arrangement of neutrons.
C. the number of electrons in the outermost shell.
D. the number of protons and neutrons.
E. the number of electrons in the inner shell.
It is the outermost shell of an atom that can potentially react with electrons in the outermost
shells of other atoms. The protons and neutrons remain in the nucleus and do not engage in
chemical reactions.
Bloom’s Level: 1. Remember
Learning Outcome: 02.01.03 Describe how variations in an atomic nucleus account for its
physical properties.
Section: 02.01
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-3
4. The atomic mass of an element
A. is determined by its protons and neutrons.
B. equals the number of protons plus the number of electrons.
C. equals the number of neutrons.
D. changes after each reaction.
E. depends on the number of electrons in the outermost shell.
The atomic mass is essentially the sum of protons and neutrons in the nucleus; it is not
changed by chemical reactions. The mass of electrons is negligible.
Bloom’s Level: 1. Remember
Learning Outcome: 02.01.02 Use the periodic table to determine relationships among atomic
number and mass number.
Section: 02.01
Topic: Chemistry
5. The nucleus of an atom contains
A. neutrons and electrons.
B. electrons only.
C. protons, neutrons, and electrons.
D. protons and neutrons.
E. neutrons only.
The nucleus contains protons and neutrons; electrons orbit the nucleus.
Bloom’s Level: 1. Remember
Learning Outcome: 02.01.01 Describe how protons, neutrons, and electrons relate to atomic
structure.
Section: 02.01
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-4
6. Isotopes of a given element have
A. the same number of protons but differ in atomic mass.
B. the same atomic mass but different number of protons.
C. different number of electrons.
D. the same number of protons and atomic mass.
E. the same number of neutrons.
Isotopes are atoms of the same element that differ in the number of neutrons only; thus, they
have the same atomic number but different atomic masses.
Bloom’s Level: 1. Remember
Learning Outcome: 02.01.02 Use the periodic table to determine relationships among atomic
number and mass number.
Section: 02.01
Topic: Chemistry
7. The isotope 14
6C has
A. 14 electrons.
B. 6 neutrons.
C. 8 protons.
D. 8 neutrons.
E. 8 electrons.
Carbon 14 has eight neutrons, 6 protons (and thus 6 electrons), and an atomic mass of 14.
Bloom’s Level: 2. Understand
Learning Outcome: 02.01.03 Describe how variations in an atomic nucleus account for its
physical properties.
Section: 02.01
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-5
8. To measure the activity of the human brain during certain thought processes, a short-lived
radioactive sugar is injected in the carotid artery and is utilized by those cells that are most
active. This shows up on a PET scan and demonstrates the detection of
A. ionic bonds.
B. high levels of radiation.
C. covalent bonds.
D. neutrons.
E. isotopes.
The isotopes used in PET scans constitute a low level of radiation used for beneficial purposes.
Types of chemical bonds are not registered by this procedure. Although isotopes of a given
element differ in their numbers of neutrons, neutrons are not detected by PET.
Bloom’s Level: 1. Remember
Learning Outcome: 02.01.04 Identify the beneficial and harmful uses of radiation.
Section: 02.01
Topic: Chemistry
9. The difference between 12
6C and 14
6C is
A. the number of electrons.
B. the number of protons.
C. the number of neutrons.
D. the number of carbon atoms.
E. the number of ionic bonds.
Carbon 12 and carbon 14 are different isotopes of the element carbon; this means they have
the same number of protons and electrons, but they differ in the number of neutrons. The
number of bonds an isotope can form is not determined by its neutrons.
Bloom’s Level: 1. Remember
Learning Outcome: 02.01.03 Describe how variations in an atomic nucleus account for its
physical properties.
Section: 02.01
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-6
10. Which of the following molecules is NOT a compound?
A. H2O
B. HCl
C. H2
D. C6H12O6
E. NaOH
A compound consists of atoms of two or more different elements bound together; H2 is two
molecules of the same element (hydrogen) bound together.
Bloom’s Level: 2. Understand
Learning Outcome: 02.02.01 Describe how elements are combined into molecules and
compounds.
Section: 02.02
Topic: Chemistry
11. Which of the following statements is NOT true of chemical bonds?
A. Both ionic and covalent bonds involve electrons in the outer shell.
B. Covalent bonds share electrons between two atoms.
C. An atom involved in an ionic bond has an unequal number of electrons and protons.
D. Salts are covalently bonded.
E. The atoms in a molecule of water (H2O) are covalently bound together.
Salts, such as sodium chloride (NaCl) are ionic compounds. All the other answer choices are
accurate statements.
Bloom’s Level: 1. Remember
Learning Outcome: 02.02.02 List the different types of bonds that occur between elements.
Section: 02.02
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-7
12. An ion is an atom that
A. exists in a gaseous state.
B. has a net charge.
C. does not have a net charge.
D. shares electrons with other atoms.
E. shares neutrons with other atoms.
An ion has more or less electrons than a neutral atom of the same element, so it has a net
positive or negative charge.
Bloom’s Level: 1. Remember
Learning Outcome: 02.02.02 List the different types of bonds that occur between elements.
Section: 02.02
Topic: Chemistry
13. If neutral atoms become positive ions, they
A. gain electrons.
B. lose electrons.
C. gain protons.
D. lose protons.
E. do not change.
The electron transfer is what will determine if an atom becomes a positive or negative
ion. To become a positive ion an atom will need to lose electrons so there are more protons
than electrons.
Bloom’s Level: 2. Understand
Learning Outcome: 02.02.01 Describe how elements are combined into molecules and
compounds.
Section: 02.02
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-8
14. When an ionic bond forms, electrons are
A. lost from both atoms.
B. gained by both atoms.
C. shared equally by both atoms.
D. totally lost from the paired atoms.
E. transferred from one atom to another.
Ionic compounds form when one atom gives up an electron, which is accepted by the other
member of the pair. Now that one atom is a positively-charged ion and the other is a
negatively-charged ion, the two atoms are attracted to one another.
Bloom’s Level: 1. Remember
Learning Outcome: 02.02.02 List the different types of bonds that occur between elements.
Section: 02.02
Topic: Chemistry
15. Calcium chloride, CaCl2, is an ionic compound in which
A. one chlorine atom transferred an electron to the other chlorine atom.
B. each chlorine atom has lost electrons.
C. calcium has two extra electrons in its innermost shell.
D. calcium has gained two electrons.
E. calcium has lost two electrons.
In the ionic compound CaCl2, calcium has transferred two electrons from its outermost shell,
becoming a calcium ion (Ca2+). One of the electrons has been accepted by each chlorine atom,
so they become chloride ions (Cl
–
).
Bloom’s Level: 1. Remember
Learning Outcome: 02.02.02 List the different types of bonds that occur between elements.
Section: 02.02
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-9
16. A covalent bond is
A. a type of bond that results in ionic compounds.
B. the transfer of electrons from one atom to another.
C. a sharing of electrons between two atoms.
D. an attraction of charged atoms.
E. a sharing of protons between two atoms.
A covalent bond results when two atoms share electrons in such a way that each atom has
eight electrons in its outermost shell. In contrast, ionic compounds result from the complete
transfer of electrons between bonded atoms.
Bloom’s Level: 1. Remember
Learning Outcome: 02.02.02 List the different types of bonds that occur between elements.
Section: 02.02
Topic: Chemistry
17. Potassium, a metal with one electron in the outermost shell, will react with how many
chlorine atoms? (Chlorine is a nonmetal with seven electrons in the outermost shell.)
A. 5
B. 7
C. 1
D. 2
E. 3
Potassium will attain stability by transferring the one electron in its outermost shell to
chlorine, which needs only one more electron in its outermost shell to become stable. The
result will be a potassium ion (K+
) and a chloride ion (Cl
–
). The two oppositely-charged ions
will be attracted to one another, thus forming an ionic compound.
Bloom’s Level: 2. Understand
Learning Outcome: 02.02.01 Describe how elements are combined into molecules and
compounds.
Section: 02.02
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-10
18. Polar covalent bonds result from
A. unequal sharing of electrons in a covalent bond.
B. equal sharing of electrons in a covalent bond.
C. equal sharing of electrons in an ionic bond.
D. unequal sharing of electrons in an ionic bond.
E. hydrogen bonding between molecules.
Covalent bonds result from sharing of electrons between bound atoms; when the sharing is
unequal, it is a polar bond, and when the sharing is equal, it is a nonpolar bond. Ionic bonds
are a different type of chemical bond from covalent bonds; in an ionic bond, one or
more electrons are completely transferred from one member of the compound to the other(s).
Hydrogen bonding is a relatively weak attraction between hydrogen in one molecule and a
highly electronegative atom (such as O or N) in an adjacent molecule.
Bloom’s Level: 1. Remember
Learning Outcome: 02.02.02 List the different types of bonds that occur between elements.
Section: 02.02
Topic: Chemistry
19. Which of the following statements about hydrogen bonding is incorrect?
A. Hydrogen bonding occurs only between water molecules.
B. Hydrogen bonds are easily broken.
C. Hydrogen bonding can occur between different molecules or within the same molecule.
D. Most hydrogen bonds involve hydrogen and oxygen or nitrogen.
E. The structure of a large, complex molecule can be influenced by hydrogen bonding.
Hydrogen bonding is not limited to bonding between adjacent water molecules. For example,
hydrogen bonds can form between hydrogen in water and nitrogen in ammonia, or between
the two strands of a DNA molecule. Hydrogen bonds are important in determining the shape
of large, complex molecules such as proteins. Even so, hydrogen bonds are relatively weak
when compared to ionic or covalent bonds, and are easily broken.
Bloom’s Level: 1. Remember
Learning Outcome: 02.02.02 List the different types of bonds that occur between elements.
Section: 02.02
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-11
20. Which of the following is not a property of water that results from hydrogen bonding?
A. The temperature of water changes very slowly.
B. Many polar substances dissolve in water.
C. Water molecules have cohesiveness.
D. Ice melts at -100ï‚°C.
E. Water has a high surface tension.
Due to its hydrogen bonding, water melts at 0ï‚°C instead of -100ï‚°C. All the other answer
choices are accurate statements.
Bloom’s Level: 1. Remember
Learning Outcome: 02.03.01 Evaluate which properties of water are important for biological
life.
Section: 02.03
Topic: Chemistry
21. Water is a liquid at room temperature. This is due to
A. ionic bonding of the atoms in the water molecule.
B. covalent bonding in the water molecule.
C. covalent bonding between water molecules.
D. hydrogen bonding within the water molecule.
E. hydrogen bonding between water molecules.
Hydrogen bonding between water molecules keeps water in a liquid state at temperatures
typically found on the Earth’s surface, including room temperature. Water molecules do not
covalently bond to one another, and the water molecule is too small to permit intramolecular
hydrogen bonds to form. Water molecules do ionize, but this does not influence the fluid
nature of water.
Bloom’s Level: 3. Apply
Learning Outcome: 02.03.01 Evaluate which properties of water are important for biological
life.
Section: 02.03
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-12
22. The moon lacks life and varies dramatically in temperature. If we could keep a layer of
water spread on the surface of the moon, what effect would it have?
A. Life would be possible but it would have to withstand these extremes in temperature.
B. Water would absorb and hold heat and moderate the temperature extremes.
C. The temperatures would drop to the lower extremes.
D. Because water has a high heat of vaporization, the temperatures would rise to the upper
extremes.
E. Physical conditions would remain the same.
Water has a high heat capacity; this serves to moderate temperature changes. Although water
does have a high heat of vaporization, this also has a moderating effect, and would prevent
temperatures from rising to the highest extremes.
Blooms Level: 4. Analyze
Learning Outcome: 02.03.01 Evaluate which properties of water are important for biological
life.
Section: 02.03
Topic: Chemistry
23. In water, a weak hydrogen bond occurs between hydrogen in one molecule and
A. an oxygen atom in the same molecule.
B. an oxygen atom in a different molecule.
C. a hydrogen atom in the same molecule.
D. a hydrogen atom in a different molecule.
E. either hydrogen and oxygen atoms of different molecules.
Because water molecules are polar, and each oxygen has slight negative charge and the
hydrogen a slight positive charge, hydrogen bonding occurs between a hydrogen atom of one
water molecule and the oxygen of another.
Bloom’s Level: 1. Remember
Learning Outcome: 02.02.03 Compare the relative strengths of ionic, covalent, and hydrogen
bonds.
Section: 02.02
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-13
24. You notice that rain water forms “beads” on your car. This is an example of what property
of water?
A. cohesion
B. dissociation
C. high heat of vaporization
D. adhesion
E. solvent
The formation of water beads on the surface of a car is due to the cohesiveness of water
molecules for one another, thanks to hydrogen bonding. Adhesion is attraction of water
molecules for a surface–a property that is not demonstrated here, since the surface of the car
(especially a freshly-waxed car) repels the water. The high heat of vaporization and solvent
capabilities of water are not apparent in this example. Water does dissociate into ions, but this
does not manifest in the formation of beads.
Bloom’s Level: 1. Remember
Learning Outcome: 02.03.01 Evaluate which properties of water are important for biological
life.
Section: 02.03
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-14
25. Hydrogen bonding produces which following property of water?
A. Boiling at a lower temperature than expected.
B. Water is less dense as ice than as liquid water.
C. Water absorbs heat with a large change in temperature.
D. Water releases heat with a large change in temperature.
E. Water can be more dense as ice than as liquid water.
Due to the increased stability of hydrogen bonding at lower temperatures, water is less dense
as ice than as liquid water. Water can absorb and release heat, but with a relatively small
change in temperature. Due to hydrogen bonding, water boils at 100ï‚°C; without hydrogen
bonding, it would boil at -91ï‚°C.
Bloom’s Level: 1. Remember
Learning Outcome: 02.03.01 Evaluate which properties of water are important for biological
life.
Section: 02.03
Topic: Chemistry
26. The water strider is an insect that skates across the water without sinking. The tips of its
feet must be coated with molecules that are
A. ions.
B. hydrophilic.
C. hydrophobic.
D. basic.
E. acidic.
The water strider’s feet should be coated with hydrophobic molecules to repel water; a
hydrophilic coating would cause the insect to stick to the surface of the water and sink. Ions,
acids and bases are hydrophilic.
Bloom’s Level: 3. Apply
Learning Outcome: 02.03.01 Evaluate which properties of water are important for biological
life.
Section: 02.03
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-15
27. The lower the pH
A. the lower the hydrogen ion (H+
) concentration.
B. the more acidic the solution.
C. the higher the pH.
D. the greater the hydroxide ion (OH-
) concentration.
E. the closer the hydroxide ion (OH-
) concentration comes to equaling the hydrogen ion (H+
)
concentration.
The pH scale is based on hydrogen ion (H+
) concentration. The higher the concentration of H+
(and the lower the concentration of OH
–
, hydroxide), the lower the pH, and the more acidic
the solution.
Bloom’s Level: 1. Remember
Learning Outcome: 02.03.02 Identify common acidic and basic substances.
Section: 02.03
Topic: Chemistry
28. Since pure water is neutral, it contains
A. no hydrogen ions (H+
).
B. no hydroxide ions (OH-
).
C. neither hydrogen ions (H+
) nor hydroxide ions (OH-
).
D. an equal number of hydrogen ions (H+
) and hydroxide ions (OH-
).
E. seven times more hydrogen ions (H+
) than hydroxide ions (OH-
).
Pure water is neutral, with a pH of 7 (midway between 0 and 14 on the pH scale), meaning
that it has equal concentrations of hydrogen ions (H+
) and hydroxide ions (OH-).
Bloom’s Level: 2. Understand
Learning Outcome: 02.03.02 Identify common acidic and basic substances.
Section: 02.03
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-16
29. The pH of blood is slightly basic. Which of the following would therefore be an expected
pH for blood?
A. 6.4
B. 4.6
C. 4.7
D. 7.4
E. 13.8
The pH scale ranges from 0 to 14, with 7 being neutral. Numbers lower than 7 are acidic, and
those higher than 7 are basic. Thus, a pH of 7.4 would be slightly basic.
Bloom’s Level: 3. Apply
Learning Outcome: 02.03.02 Identify common acidic and basic substances.
Section: 02.03
Topic: Chemistry
30. Potassium hydroxide (KOH) almost completely dissociates in aqueous solution into K+
and OHand is therefore a
A. strong acid.
B. strong base.
C. weak base.
D. weak acid.
E. nonpolar covalent molecule.
Because potassium hydroxide dissociates completely and adds hydroxide ions (OH-) to an
aqueous solution, it is a strong base. A weak base would not dissociate so completely. An acid
would contribute hydrogen ions (H+
) to an aqueous solution. Potassium hydroxide is an ionic
compound; a nonpolar covalent molecule would not dissociate or dissolve in an aqueous
solution.
Blooms Level: 4. Analyze
Learning Outcome: 02.03.02 Identify common acidic and basic substances.
Section: 02.03
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-17
31. Which statement regarding acids and bases is correct?
A. Acids increase the pH, and bases decrease the pH.
B. Acids increase the proportion of hydrogen ions (H+
), and bases reduce the proportion of H
+
.
C. Acids are harmful, but bases are not harmful.
D. Acids combine with bases to form buffers.
E. Acids combine with bases to form sugars.
Acids raise the hydrogen ion (H+
) content of a solution, while bases reduce the proportion of
H
+
. The lower the pH, the more acidic the solution, and the higher the pH, the more basic the
solution. Strong acids and bases are both harmful. When acids combine with bases, salts
result.
Bloom’s Level: 1. Remember
Learning Outcome: 02.03.02 Identify common acidic and basic substances.
Section: 02.03
Topic: Chemistry
32. Buffers
A. are strong acids or bases.
B. keep the pH within normal limits.
C. release large amounts of hydrogen ions (H+
).
D. lower the pH.
E. increase the pH.
Buffers are the chemicals or combinations of chemicals that keep pH within normal limits.
Weak acids and bases may be used as buffers, not strong ones, which would greatly influence
the H+
concentration of the solution and thereby raise or lower the pH.
Bloom’s Level: 1. Remember
Learning Outcome: 02.03.03 Describe how buffers are important to living organisms.
Section: 02.03
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-18
33. Aspirin is acetyl salicylic acid and can therefore pose a problem to people who have ulcers.
Bufferin uses a buffer to neutralize this effect by
A. substituting another ingredient for the acetyl salicylic acid.
B. adding a drug to stimulate the immune system.
C. adding salts to neutralize the acid.
D. adding an equal amount of hydroxide (OH-
) ions.
E. adding chemicals that take up excess hydrogen (H+
) ions.
Bufferin contains a buffering system to bind the excess H+
from the aspirin (acetyl salicylic
acid). This would not be a salt; salts form when acids and bases react.
Bloom’s Level: 3. Apply
Learning Outcome: 02.03.03 Describe how buffers are important to living organisms.
Section: 02.03
Topic: Chemistry
34. Rain falling in the northeastern U.S. has a pH between 5.0 and 4.0. Normally, rainwater
has a pH of about 5.6. Which of the following statements is not correct?
A. The pH of the rainwater has changed from neutral to acidic.
B. The pH of the rainwater has become more acidic.
C. The hydrogen ion (H+
) content of the rainwater has increased.
D. The proportion of hydroxide ions (OH-
) in the rainwater has declined.
E. The rainwater with a pH of 4.0 is ten times more acidic than the rainwater with a pH of 5.0.
The pH of rainwater is normally acidic (5.6) not neutral (7). All the other answer choices are
accurate statements.
Bloom’s Level: 2. Understand
Learning Outcome: 02.03.02 Identify common acidic and basic substances.
Section: 02.03
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-19
35. Organic molecules
A. always contain carbon.
B. always contain hydrogen.
C. always contain carbon and hydrogen.
D. are found only in organisms, hence their name.
E. are always food molecules.
Organic molecules, by definition, must contain both carbon and hydrogen. They are found in
organisms and in food, but can also be made in a laboratory.
Bloom’s Level: 1. Remember
Learning Outcome: 02.04.01 Compare inorganic molecules to organic molecules.
Section: 02.04
Topic: Chemistry
36. Which of the following molecules is inorganic?
A. CH4
B. CO2
C. C6H12O6
D. C12H22O12
E. C6H6
Carbon dioxide (CO2) is inorganic because, although it contains carbon, it does not contain
hydrogen. All the other molecules contain both carbon and hydrogen and are therefore
organic.
Bloom’s Level: 2. Understand
Learning Outcome: 02.04.01 Compare inorganic molecules to organic molecules.
Section: 02.04
Topic: Chemistry
Chapter 02 – The Molecules of Cells
2-20
37. One carbon atom can form covalent bonds with up to ___ other atoms to form an organic
molecule.
A. 2
B. 3
C. 4
D. 6
E. 8
Carbon, with an atomic number of 6, has 4 electrons in its outermost shell. Thus, carbon can
form 4 single covalent bonds with other atoms.
Bloom’s Level: 1. Remember
Learning Outcome: 02.04.01 Compare inorganic molecules to organic molecules.
Section: 02.04
Topic: Chemistry
38. Two molecules of glucose combine to form a disaccharide molecule during a(n) ________
reaction.
A. dehydration
B. hydrolysis
C. hydrogen bond
D. ionic bond
E. inert
The glucose molecules are monomers; forming a covalent bond between them requires a
dehydration reaction. A hydrolysis reaction could be used to break the disaccharide apart into
individual glucose monomers. An inert material would not react at all.
Bloom’s Level: 1. Remember
Learning Outcome: 02.04.03 Recognize how monomers are joined to form polymers.
Section: 02.04
Topic: Chemistry