Chapter Chapter 2: The Chemical Basis of Life
 
Chapter Quiz
 

1 .       Why are biologists so interested in chemistry? (2.0) [Hint]

 Chemicals are the fundamental parts of all living things.
 Most chemicals are harmful to living things.
 They know little about life except the chemicals it is made from.
 If you understand the chemistry of life, you can make a lot of money.
 Everything about life can be known by understanding its chemistry.
2 .       There are _____ naturally occurring elements. (2.1) [Hint]

 92
 45
 230
 25
 108
3 .       K is the chemical symbol for __________ and P is the symbol for __________. (2.1) [Hint]

 phosphorus ... sodium
 sodium ... potassium
 potassium ... phosphorus
 magnesium ... phosphorus
 iron ... potassium
4 .       Which one of the following is NOT one of the four most common elements found in living systems? (2.1) [Hint]

 H
 N
 C
 Ne
 all of the above
5 .       A substance that cannot be broken down into other substances by ordinary chemical procedures is a(n) _____. (2.1) [Hint]

 molecule
 element
 compound
 buffer
 cell
6 .       Which of the following statements is true about compounds? (2.3) [Hint]

 Twenty-five compounds are essential to life.
 They are smaller than any one element.
 They have polarity.
 They contain two or more elements in a fixed ratio to each other.
 All of the above.
7 .       Which of the following is the smallest in volume? (2.4) [Hint]

 the nucleus of an oxygen atom
 a water molecule
 a proton
 an ice crystal
 the electron cloud of an oxygen atom
8 .       Which one of the following has negligible mass? (2.4) [Hint]

 proton
 neutron
 electron
 atom
 element
9 .       Which one of the following subatomic particles has appreciable mass and lacks a charge? (2.4) [Hint]

 proton
 neutron
 electron
 element
 molecule
10 .       The number of protons in an uncharged atom _____. (2.4) [Hint]

 equals the number of electrons
 equals the number of neutrons
 varies with the different isotopes
 equals the number of electrons in the outer orbital of the atom
 determines its mass number
11 .       Consider a hypothetical atom with an atomic number of 4 and a net electronic charge of +1. It has 4 protons. How many neutrons does this atom have? (2.4) [Hint]

 2
 4
 8
 The answer cannot be determined from the information.
 none of the above
12 .       A particular carbon isotope has an atomic number of 6 and an atomic weight of 14. The respective number of neutrons, protons, and electrons it has is _____. (2.4) [Hint]

 6, 8, 6
 6, 6, 8
 8, 6, 6
 8, 6, 8
 8, 6, 4
13 .       An element has 8 protons, 9 neutrons, and 8 electrons. Its atomic number and its mass number, respectively, are _____. (2.4) [Hint]

 8 and 16
 8 and 17
 9 and 16
 9 and 17
 16 and 8
14 .       Two atoms of the same element must have the same number of _____. (2.4) [Hint]

 neutrons
 protons
 electrons
 neutrons plus protons
 protons plus electrons
15 .       An uncharged atom of nitrogen (atomic number = 7) has ___________. (2.4) [Hint]

 7 neutrons
 7 protons and 7 neutrons
 7 neutrons and 7 electrons
 7 protons and 7 electrons
 7 valence electrons
16 .       Isotopes of an element will always differ in _____. (2.4) [Hint]

 atomic number
 atomic mass number
 number of electrons
 all of the above
 none of the above
17 .       Phosphorus–32 (radioactive) has __________ than phosphorus–35 (normal). (2.4) [Hint]

 3 more neutrons
 3 more protons
 3 fewer neutrons
 3 fewer protons
 three more atoms
18 .       The most common form of calcium has 20 protons, 20 neutrons, and 20 electrons. Which of the following elements would be an isotope of calcium? (2.4) [Hint]

 an atom with 21 protons, 20 neutrons, and 21 electrons
 an atom with 20 protons, 20 neutrons, and 18 electrons
 an atom with 20 protons, 21 neutrons, and 20 electrons
 none of the above
 all of the above
19 .       Which one of the following always has a positive charge? (2.4) [Hint]

 proton
 neutron
 electron
 atom
 element
20 .       Changing the number of _____ would change an atom into an atom of a different element. (2.4) [Hint]

 bonds formed by an atom
 electrons circling the nucleus of an atom
 protons in an atom
 particles in the nucleus of an atom
 neutrons in an atom
21 .       Which of the following is NOT a characteristic that makes radioactive tracers useful in medical diagnoses and clinical research? (2.5) [Hint]

 They are incorporated into reactions in living material.
 They are easily detectable in minute amounts.
 They damage or destroy molecules.
 Living cells cannot distinguish them from nonradioactive isotopes.
 They can be used with PET scanners.
22 .       Researchers studying the effects of toxic wastes knew that animals were poisoned by the heavy metal cadmium, but they wanted to know where cadmium accumulated in the body. They could find out by _____. (2.5) [Hint]

 tracing the movement of cadmium isotopes in test animals
 measuring the size of cadmium atoms
 finding out whether cadmium atoms form ionic or covalent bonds
 finding out whether cadmium is acidic in water
 determining the number of bonds formed by cadmium atoms
23 .       The chemical bonding and reactivity characteristics of an element depend mostly on the _____. (2.6) [Hint]

 number of electrons in its outer shell
 number of electron shells present in the atoms
 mean energy level of its electrons
 degree to which it has more or fewer electrons than protons
 number of protons plus the number of neutrons
24 .       Some groups of elements react chemically in similar ways. For example, the chemical reactions of sodium and the chemistry of lithium are similar, as are the chemistries of chlorine and iodine. These similar chemistries are caused when different elements have similar ___________. (2.6) [Hint]

 atomic size
 numbers of outer-shell electrons
 numbers of electrons
 energy content per electron
 atomic number
25 .       For most atoms, a stable configuration of electrons is attained when the atom ___________. (2.6) [Hint]

 has as many protons as neutrons
 has moved all its electrons to its outermost shell
 achieves a zero net charge
 has 8 electrons in its outermost shell
 none of the above
26 .       Atomic oxygen has an atomic number of 8. It has __________ electrons in its outermost electron shell. (2.6) [Hint]

 2
 6
 8
 10
 none of the above
27 .       An atom that normally has _____ in its outer shell would tend not to form chemical bonds with other atoms. (2.6) [Hint]

 1 electron
 3 electrons
 4 electrons
 6 electrons
 8 electrons
28 .       When the proton number and electron number are unequal, the atom or molecule _____. (2.7) [Hint]

 forms a covalent bond with another atom
 is an ion
 is an isotope.
 gains or loses a proton
 gains or loses a neutron
29 .       A sodium atom has a mass number of 23. Its atomic number is 11. How many electrons does it have if it is not an ion? (2.7) [Hint]

 11
 12
 22
 23
 34
30 .       Fluorine atoms tend to take electrons from any atoms that come near. As a result, fluorine atoms _____. (2.7) [Hint]

 tend to become positively charged
 are nonpolar
 do not react readily with other atoms
 tend to form ionic bonds
 are not very electronegative
31 .       Ionic bonds form as a result of ___________. (2.7) [Hint]

 attraction between atoms that have opposite charges
 attraction between hydrogen and other atoms that share electrons unequally
 sharing of electron pairs between atoms
 sharing of single electrons between atoms
 the motion of electrons
32 .       Which of these describes a covalent bond? (2.8) [Hint]

 Two or more atoms share electron pairs.
 It involves an atom that gains an electron.
 Molecules linked by covalent bonds are less dense when in solid form than when in liquid form.
 A hydrogen atom with a partial positive charge is attracted to another atom with a partial negative charge.
 It involves an atom that loses an electron.
33 .       A polar covalent bond is a bond that _____. (2.9) [Hint]

 is found only in H2O
 is found only in molecules containing oxygen
 shares electrons equally between atoms
 ionizes
 has shared electrons pulled closer to the more electronegative atom, thereby producing slight charges on the molecule.
34 .       A covalent bond is likely to be polar if _____. (2.9) [Hint]

 the two atoms sharing electrons are equally electronegative
 one of the atoms sharing electrons is much more electronegative
 it is between two atoms that are both very strong electron acceptors
 the two atoms sharing electrons are of the same element
 it is between two atoms that are both very strong electron donors
35 .       The partial charges on a water molecule occur because of _____. (2.9) [Hint]

 the unequal sharing of electrons between hydrogen and oxygen
 the achievement of a stable configuration by one atom of a bond but not by the other partner
 covalent bonding
 ionic bonding
 the high electronegativity of hydrogen
36 .       Water is a polar molecule. This means that _____. (2.9) [Hint]

 the opposite ends of the molecule have opposite charges
 water molecules are linear, like a pole
 water is one of the many nonpolar molecules
 the atoms in water have equal electronegativities
 all of the above
37 .       Which is NOT involved in, or is NOT relevant to, hydrogen bonding? (2.10) [Hint]

 hoarding of electrons by one atom more than another
 electronegativity
 attraction between unlike partial charges
 loss of electrons
 polar molecules
38 .       Hydrogen bonds occur when ___________. (2.10) [Hint]

 a molecule with partial charges contacts a molecule without partial charges
 a molecule with a low molecular weight is completely enclosed in a molecule with high molecular weight
 two atoms achieve stable electron configurations by sharing electrons with each other
 partial opposite charges on molecules come close enough to attract each other
 none of the above
39 .       In a group of water molecules, hydrogen bonds form between _____. (2.10) [Hint]

 two hydrogen atoms in different water molecules
 the oxygen atoms in different water molecules
 the oxygen atom in one molecule and a hydrogen atom in another molecule
 the hydrogen atoms in a single water molecule
 none of the above
40 .       A hydrogen bond ___________. (2.10) [Hint]

 is one in which two hydrogens bond to each other
 is one in which hydrogen is strongly attracted to a positively charged atom
 is a function of nonpolar interactions
 is weak
 is one of the strongest bonds known
41 .       Water molecules have a polarity that allows them to bond to each other with loose bonds called _____. (2.10) [Hint]

 hydrogen bonds
 ionic bonds
 acid bonds
 nonpolar bonds
 none of the above
42 .       What do cohesion and surface tension have in common with reference to water? (2.11) [Hint]

 All are results of the structure of the hydrogen atom.
 All are produced by covalent bonding.
 All are properties related to hydrogen bonding.
 All have to do with ionic interactions.
 All are aspects of a crystalline structure.
43 .       The tendency of water molecules to stick together _____. (2.11) [Hint]

 provides the surface tension that allows some insects to walk on water
 is called cohesion
 keeps water moving through the vessels in a tree trunk
 acts to moderate temperature
 all of the above
44 .       Water resists temperature change because _____. (2.12) [Hint]

 large bodies of water cannot store heat
 heating water absorbs energy by disrupting the hydrogen bonds before evaporation can occur
 evaporation of water heats the surface it leaves
 hydrogen bonding increases water's ability to vaporize
 none of the above
45 .       Because the molecules of water are farther apart in ice than in liquid water, _____. (2.13) [Hint]

 ice floats
 ice is denser than liquid water
 ice expands when it melts
 ice vaporizes before liquid water does
 all of the above
46 .       Cells are surrounded by water, and cells themselves are about 70-95% water. As a result, _____. (2.14) [Hint]

 the temperature of living things tends to change relatively slowly
 a variety of nutrient molecules are readily available as dissolved solutes
 waste products produced by cell metabolism can be easily removed
 dissolved substances can be easily transported within the cell, or between cells in multicellular organisms
 all of the above
47 .       The most widely effective solvent for organisms is a material that is _____. (2.14) [Hint]

 polar
 nonpolar
 ionic
 pigmented
 volatile
48 .       Sodium chloride (NaCl) dissolves in water because water molecules _____. (2.14) [Hint]

 have a high specific heat
 lose electrons
 are polar
 have a pH near 7
 are less dense than NaCl molecules
49 .       Adding acid to a solution ____.(2.15) [Hint]

 increases the hydrogen ion concentration and raises the pH
 increases the hydrogen ion concentration and lowers the pH
 decreases the hydrogen ion concentration and raises the pH
 decreases the hydrogen ion concentration and lowers the pH
 either increases or decreases the pH, depending on the original acidity
50 .       Which of the following dissociations is that of an acid? (2.15) [Hint]

 H2O --> H+ + OH-
 NaOH --> Na+ + OH-
 HF --> H+ + F-
 NH3 + H+ --> NH4+
 HCO3- + H+ --> H2CO3
51 .       A glass of grapefruit juice, at pH 3, contains _____ H+ as a glass of tomato juice, at pH 4. (2.15) [Hint]

 one-tenth as much
 half as much
 twice as much
 three times as much
 ten times as much
52 .       An acid is _____. (2.15) [Hint]

 any compound with a pH
 any compound that accepts hydrogen ions
 a material that resists pH changes
 a compound that donates hydrogen ions to a solution
 a solution with a pH between 7 and 14
53 .       Something that resists a change in pH is called a(n) _____. (2.15) [Hint]

 isoproton
 buffer
 proton sink
 acid
 base
54 .       Adding a base tends to _____ of a solution. (2.15) [Hint]

 lower hydrogen ion concentration and lower the pH
 lower hydrogen ion concentration and increase the pH
 increase hydrogen ion concentration and lower the pH
 increase the hydrogen ion concentration and increase the pH
 lower the hydroxide ion concentration and lower the pH
55 .       Pure water has a pH of 7, but acid precipitation has a pH close to 3. This means that acid rain has a concentration of hydrogen ions that is __________ times the hydrogen ion concentration of pure water. (2.15) [Hint]

 0.0001
 0.25
 4
 10,000
 -4
56 .       A pH of 6 is how many times more acidic than a pH of 9? (2.15) [Hint]

 300
 1,000
 3
 100
 none of the above
57 .       Select the statement that best describes a buffer. (2.15) [Hint]

 A buffer accepts hydrogen ions when they are in excess and donates hydrogen ions when they have been depleted.
 A buffer causes acidic solutions to become alkaline, and alkaline solutions to become acidic.
 A buffer prevents the pH of a solution from changing when an acid or base is added.
 A buffer stabilizes the pH of a solution by preventing acids or bases from dissociating.
 Buffered solutions are always neutral, with a pH of 7.
58 .       Which of the following statements is true about acid precipitation? (2.16) [Hint]

 It can be eliminated if we burn fossil fuels instead of using solar or nuclear power.
 It affects bodies of water but has little effect on the land.
 It has the most pronounced effect on lakes and streams in the early spring.
 Building taller smokestacks can clean it up.
 None of the above.