Chemistry, 6e (McMurry/Fay)
Chapter 2 Atoms, Molecules, and Ions
2.1 Multiple-Choice Questions
1) According to history, the concept that all matter is composed of atoms was first proposed by
A) the Greek philosopher Democritus, but not widely accepted until modern times.
B) Dalton, but not widely accepted until the work of Mendeleev.
C) Dalton, but not widely accepted until the work of Einstein.
D) Dalton, and widely accepted within a few decades.
2) The observation that 15.0 g of hydrogen reacts with 120.0 g of oxygen to form 135.0 g of water is
evidence for the law of
A) definite proportions.
B) energy conservation.
C) mass conservation.
D) multiple proportions.
3) The observation that 4.0 g of hydrogen reacts with 32.0 g of oxygen to form a product with
O:H mass ratio = 8:1, and 6.0 g of hydrogen reacts with 48.0 g of oxygen to form the same product
with O/H mass ratio = 8:1 is evidence for the law of
A) definite proportions.
B) energy conservation.
C) mass conservation.
D) multiple proportions.
4) Methane and oxygen react to form carbon dioxide and water. What mass of water is formed if 3.2 g of
methane reacts with 12.8 g of oxygen to produce 8.8 g of carbon dioxide?
A) 7.2 g
B) 8.8 g
C) 14.8 g
D) 16.0 g
5) Sodium metal and water react to form hydrogen and sodium hydroxide. If 5.98 g of sodium react with
water to form 0.26 g of hydrogen and 10.40 g of sodium hydroxide, what mass of water was consumed
in the reaction?
A) 4.68 g
B) 5.98 g
C) 10.14 g
D) 10.66 g
6) A sample of pure lithium carbonate contains 18.8% lithium by mass. What is the % lithium by mass
in a sample of pure lithium carbonate that has twice the mass of the first sample?
A) 9.40%
B) 18.8%
C) 37.6%
D) 75.2%
7) A sample of pure calcium fluoride with a mass of 15.0 g contains 7.70 g of calcium. How much
calcium is contained in 45.0 g of calcium fluoride?
A) 2.56 g
B) 7.70 g
C) 15.0 g
D) 23.1 g
8) The observation that hydrogen and oxygen can react to form two compounds with different chemical
and physical properties, one having an O:H mass ratio = 8:1 and the other having an O:H mass ratio =
16:1 is consistent with the law of
A) definite proportions.
B) energy conservation.
C) mass conservation.
D) multiple proportions.
9) Which of the following statements is not a postulate of Dalton’s atomic theory?
A) Each element is characterized by the mass of its atoms.
B) Atoms are composed of protons, neutrons, and electrons.
C) Chemical reactions only rearrange atomic combinations.
D) Elements are composed of atoms.
10) Which of the following is a part of Dalton’s atomic theory?
A) Atoms are rearranged but not changed during a chemical reaction.
B) Atoms break down during radioactive decay.
C) Atoms contain protons, neutrons, and electrons.
D) Isotopes of the same element have different masses.
11) Which of the following is not explained by Dalton’s atomic theory?
A) conservation of mass during a chemical reaction
B) the existence of more than one isotope of an element
C) the law of definite proportions
D) the law of multiple proportions
12) Elements A and Q form two compounds, AQ and A2Q3. The mass ratio (mass Q)/(mass A) for AQ
is 0.574. What is the mass ratio (mass Q)/(mass A) for A2Q3?
A) 0.383
B) 0.861
C) 1.16
D) 2.61
13) Elements A and Q form two compounds, AQ and A2Q. Which of the following must be true?
A) (mass Q)/(mass A) is one for AQ, and 1/2 for A2Q.
B) (mass Q)/(mass A) for AQ must equal (mass Q)/(mass A) for A2Q.
C) (mass Q)/(mass A) for AQ must be 2 times (mass Q)/(mass A) for A2Q.
D) (mass Q)/(mass A) for AQ must be 1/2 (mass Q)/(mass A) for A2Q.
14) Elements A and Q form two compounds. The ratio (mass Q)/(mass A) for compound one is 0.271
and ratio (mass Q)/(mass A) for compound two is 0.362. If compound one has the chemical formula AQ,
what is the chemical formula for compound two?
A) A3Q4
B) A2Q3
C) AQ2
D) AQ3
15) The existence of electrons in atoms of all elements was demonstrated by
A) Millikan’s oil drop experiment.
B) Rutherford’s gold foil experiment.
C) Thomson’s cathode ray tube experiment.
D) None of these
16) The charge-to-mass ratio of an electron was established by
A) Millikan’s oil drop experiment.
B) Rutherford’s gold foil experiment.
C) Thomson’s cathode ray tube experiment.
D) None of these
17) The current model of the atom in which essentially all of an atom’s mass is contained in a very small
nucleus, whereas most of an atom’s volume is due to the space in which the atom’s electrons move was
established by
A) Millikan’s oil drop experiment.
B) Rutherford’s gold foil experiment.
C) Thomson’s cathode ray tube experiment.
D) None of these
18) The existence of neutrons in the nucleus of an atom was demonstrated by
A) Millikan’s oil drop experiment.
B) Rutherford’s gold foil experiment.
C) Thomson’s cathode ray tube experiment.
D) None of these
19) Most of the alpha particles directed at a thin gold foil in Rutherford’s experiment
A) bounced directly back from the foil.
B) passed directly through the foil undeflected.
C) passed through the foil but were deflected at an angle.
D) were absorbed by the foil.
20) Which subatomic particle has the smallest mass?
A) a proton
B) a neutron
C) an electron
D) an alpha particle
21) A proton is approximately
A) 200 times larger than an electron.
B) 2000 times larger than an electron.
C) 200 times smaller than an electron.
D) 2000 times smaller than an electron.
22) The symbol that is usually used to represent atomic number is ________.
A) A
B) N
C) X
D) Z
23) The mass number of an atom is equal to the number of
A) electrons.
B) neutrons.
C) protons.
D) protons plus neutrons.
24) Which of the following two atoms are isotopes?
A)
40Ar
18
and
40Ca
20
B)
12C
6
and
13C
6
C)
35Cl
17
and
80Br
35
D)
24Mg
12
and
12C
6
25) Which are isotopes? An atom that has an atomic number of 34 and a mass number of 76 is an
isotope of an atom that has
A) an atomic number of 32 and a mass number of 76.
B) an atomic number of 34 and a mass number of 80.
C) 42 neutrons and 34 protons.
D) 42 protons and 34 neutrons.
26) Which of the following represent isotopes?
A:
25
21
[ ] B:
21
25
[ ] C:
27
21
[ ] D:
25
23
[ ]
A) A and B
B) A and C
C) A and D
D) C and D
27) The isotope represented by
6
A) carbon-6
B) carbon-7
C) carbon-13
D) carbon-19
28) Boron-9 can be represented as
A)
9Be
4
.
B)
9B
5
.
C)
14B
5
.
D)
14B
.
29) How many protons (p) and neutrons (n) are in an atom of
90Sr
38
?
A) 38 p, 52 n
B) 38 p, 90 n
C) 52 p, 38 n
D) 90 p, 38 n
30) How many protons (p) and neutrons (n) are in an atom of calcium-46?
A) 20 p, 26 n
B) 20 p, 46 n
C) 26 p, 20 n
D) 46 p, 60 n
31) What is the chemical symbol for an atom that has 29 protons and 36 neutrons?
A) Cu
B) Kr
C) N
D) Tb
32) How many electrons are in a neutral atom of iodine-131?
A) 1
B) 53
C) 54
D) 131
33) How many protons (p), neutrons (n), and electrons (e) are in one atom of
12
?
A) 12 p, 12 n, 12 e
B) 12 p, 11 n, 12 e
C) 12 p, 11 n, 10 e
D) 12 p, 11 n, 14 e
34) Identify the chemical symbol of element Q in
80Q
34
.
A) Br
B) Hg
C) Pd
D) Se
35) The atoms of a particular element all have the same number of protons as neutrons. Which of the
following must be true?
A) The atomic weight must be a whole number.
B) The mass number for each atom must equal the atomic weight of the element.
C) The mass number must be exactly twice the atomic number for each atom.
D) All of these are true.
36) The smallest sample of carbon atoms that can be observed with the naked eye has a mass of
approximately 2 × 10-8 g. Given that 1 g = 6.02 × 1023 amu, and that carbon has an atomic weight of
12.01 amu, determine the number of carbon atoms present in the sample.
A) 1 × 1015
B) 1 × 1016
C) 1 × 1017
D) 6 × 1023
37) An element has two naturally occurring isotopes. One has an abundance of 37.4% and an isotopic
mass of 184.953 amu, and the other has an abundance of 62.6% and a mass of 186.956 amu. What is the
atomic weight of the element?
A) 185.702 amu
B) 185.954 amu
C) 186.207 amu
D) 186.956 amu
38) The element antimony has an atomic weight of 121.757 amu and only two naturally-occurring
isotopes. One isotope has an abundance of 57.3% and an isotopic mass of 120.904 amu. Based on these
data, what is the mass of the other isotope?
A) 121.757 amu
B) 122.393 amu
C) 122.610 amu
D) 122.902 amu
39) What is the standard isotope that is used to define the number of atoms in a mole?
A) 1H
B) 12C
C) 16O
D) 20Ne
40) The number of atoms of carbon in 12 g of carbon is closest to .
A) 12
B) 1022
C) 1023
D) 1024
9
41) What is the mass of one atom of the element hydrogen?
A) 2.0 g
B) 1.0 g
C) 3.4 × 10-24 g
D) 1.7 × 10-24 g
42) One mole of which element has the smallest mass?
A) Co
B) Cu
C) Ni
D) Zn
43) 24.0 g of which element contains the greatest number of atoms?
A) B
B) C
C) N
D) O
44) How many moles and how many atoms of zinc are in a sample weighing 34.9 g?
A) 0.533 mol, 8.85 ×10-25 atoms
B) 0.533 mol, 3.21 ×1023 atoms
C) 1.87 mol, 3.10 × 10-24 atoms
D) 1.87 mol, 1.13 × 1024 atoms
45) Which statement about nuclear reactions is true?
A) New elements are never produced in a nuclear reaction.
B) Nuclear reactions involve valence electrons.
C) The rate of a nuclear reaction is affected by catalysts.
D) Tremendous amounts of energy are involved in nuclear reactions.
46) The term “nucleons” refers to the number of ________ in the atom.
A) neutrons
B) protons
C) protons and neutrons
D) protons, neutrons, and electrons
47) The number of nucleons in an atom or ion is the same as the
A) atomic number.
B) charge on the atom or ion.
C) mass number.
D) none of these
48) The number of nucleons in a
236 2+
U
92
nucleus is
A) 92.
B) 144.
C) 236.
D) 328.
49) The number of neutrons in
Fe
26
is
A) 26.
B) 29.
C) 53.
D) 55.
50) “Isotopes” are atoms with the same number of ________ but different number of ________.
A) electrons, protons
B) neutrons, protons
C) protons, electrons
D) protons, neutrons
51) The rate of a nuclear reaction can be changed by
A) adding a catalyst.
B) decreasing the pressure.
C) increasing the temperature.
D) None of these
52) Which of the following statements is not correct when balancing a nuclear equation?
I. The mass numbers must be conserved on both sides of the reaction arrow.
II. The ionic charges must be conserved on both sides of the reaction arrow.
III. The atomic numbers must be conserved on both sides of the reaction arrow.
IV. The elements must be the same on both sides of the reaction arrow.
A) II only
B) II and III
C) I and III
D) II and IV
53) An alpha particle is
A)
1+
H
1
.
B)
2+
H
1
.
C)
3+
H
1
.
D)
4 2+
He
2
.
54) When a substance decays by alpha radiation, the mass number of the nucleus ________ and the
atomic number ________.
A) increases by 4, increases by 2
B) reduces by 4, reduces by 2
C) increases by 2, increases by 4
D) reduces by 2, reduces by 4
55) The nuclear decay process that involves the particle having the greatest mass is ________ emission.
A) alpha
B) beta
C) gamma
D) positron
56) A beta particle is
A)
0e
1−
.
B)
1e
0
−
.
C)
1p
1
.
D)
4He
2
.
57) When a substance decays by beta emission, the mass number of the nucleus ________ and the
atomic number ________.
A) decreases by 1, remains the same
B) increases by 1, remains the same
C) remains the same, decreases by 1
D) remains the same, increases by 1
58) Beta decay of 24Na produces a beta particle and
A) 20F.
B) 23Na.
C) 24Ne.
D) 24Mg.
59) Which of the following statements about gamma radiation is false?
A) It almost always accompanies alpha or beta emission.
B) It is a mechanism to release excess energy in the nucleus.
C) Gamma rays are high energy photons.
D) The mass number decreases by one with each gamma emitted.
60) Gamma radiation can be described as
A) a helium nucleus.
B) a negatively charged free electron.
C) high energy electromagnetic radiation.
D) a positively charged free electron.
61) A positron is
A)
1n
0
.
B)
1p
1
.
C)
0e
1
.
D)
0e
1−
.
62) Positron emission changes the atomic number of an element by
A) -2.
B) -1.
C) +1.
D) +2.
63) Which of the following statements about positrons is false?
A) The positron has same mass as an electron.
B) A positron is ejected from the nucleus during the conversion of a proton into a neutron.
C) A positron is a positive electron.
D) When positron emission occurs, the atomic number of the nucleus increases.
64) The nuclear transformation potassium-40 argon-40 + ? is classified as
A) alpha emission.
B) beta emission.
C) electron capture.
D) positron emission.
65) Which of the following statements about electron capture is false?
A) The electron is used to convert a proton to a neutron.
B) The electron involved is most likely an outer shell valence electron.
C) In electron capture decay, the atomic number decreases by one.
D) In electron capture decay, the mass number remains unchanged.
66) Which one of the following processes does not result in transmutation to another element?
A) alpha emission
B) beta emission
C) electron capture
D) gamma emission
67) Which of the following decay processes give a product nuclide whose atomic number is one less
than the starting nuclide?
A) alpha decay
B) beta decay and positron decay
C) gamma decay and beta decay
D) positron decay and electron capture
68) Which reaction below represents
15O
8
decay by positron emission?
A)
15O
8
→
0e
1−
+
15Ra
9
B)
15O
8
→
0e
1
+
15N
7
C)
15O
8
→
1e
0
−
+
16O
8
D)
15O
8
→
1e
0
+
14O
8
69) Which reaction below represents
232Th
90
decay by alpha emission?
A)
232Th
90
→
4He
2
+
228Ra
88
B)
232Th
90
→
2He
4
+
230Ra
86
C)
232Th
90
→ p +
231Ac
89
D)
232Th
90
→ n +
231Th
90
70) Which reaction below represents
44Ti
22
decay by electron capture?
A)
44Ti
22
+
1e
0
−
→
43Ti
22
B)
44Ti
22
+
1e
0
→
45Ti
22
C)
44Ti
22
+
0e
1
→
44Ti
23
D)
44Ti
22
+
0e
1−
→
44Sc
21
71) In addition to a beta particle, what is the other product of beta decay of
131I
53
?
A)
127Sb
51
B)
131Te
32
C)
131Xe
54
D)
135Cs
55
72) Tritium,
3H
1
, is formed in the upper atmosphere when
14 N
7
captures a neutron and then decays.
What is the other product of this reaction?
A)
13C
6
B)
12C
6
C)
12B
5
D)
11B
5
73) When more than 3000 known nuclides are plotted on a neutron/proton grid they make up a group
called
A) the “island of stability.”
B) the “peninsula of nuclear stability.”
C) the “sea of instability.”
D) none of these
74) Which is the only element that contains more protons than neutrons in its most abundant stable
isotope?
A) boron
B) carbon
C) hydrogen
D) mercury
75) As the atomic number of the elements increases, the ratio of neutrons to protons in stable nuclei
A) decreases.
B) stays the same.
C) increases.
D) is unrelated to stability.
76) Which one of the following statements about isotopes is false?
A) The ratio of neutrons to protons is about 1:1 for elements lighter than Ca.
B) The ratio of neutrons to protons is > 1:1 for elements heavier than Ca.
C) Nonradioactive isotopes generally have an odd number of neutrons.
D) All isotopes beyond 209Bi are radioactive.
77) Which one of the following combinations of neutrons/protons results in the lowest number of
nonradioactive (stable) isotopes?
A) even number protons/even number neutrons
B) even number protons/odd number neutrons
C) odd number protons/even number neutrons
D) odd number protons/odd number neutrons
78) Which of the following elements would you expect to have the largest number of stable isotopes?
Element number:
A) 48
B) 49
C) 50
D) 51
79) Which of the following elements would be expected to be particularly stable?
A)
40Ca
20
B)
38K
19
C)
39Ar
19
D)
37Cl
17
80) Which process decreases the neutron/proton ratio?
A) alpha emission
B) beta emission
C) electron capture
D) positron emission
81) A radioisotope has a neutron/proton ratio which is too low. Which of the following processes will
not occur for such a nucleus?
A) alpha emission
B) beta emission
C) electron capture
D) positron emission
82) A radioisotope which is neutron poor and very heavy is most likely to decay by
A) alpha emission, electron capture, or positron emission.
B) only alpha emission.
C) only electron capture.
D) only positron emission.
83) Which of the following nuclides is most likely to undergo beta decay?
A)
190Hg
80
B)
195Hg
80
C)
200Hg
80
D)
205Hg
80
84) Which of the following nuclides is most likely to decay by electron capture?
A)
190Hg
80
B)
195Hg
80
C)
200Hg
80
D)
205Hg
80
85) What nuclide is formed when
238U
92
undergoes a portion of the decay series: alpha, beta, beta,
alpha, alpha, alpha.
A)
226Ra
88
B)
222Rn
86
C)
230Th
90
D)
206Pb
86) When
222Rn
86
decays in a 5-step series the product is
210Pb
82
. How many alpha and beta particles
are emitted in the decay series?
A) 2 α, 3 β–
B) 3 α, 2 β–
C) 4 α, 1 β–
D) 1 α, 4 β–
87) A banana split is an example of
A) a compound.
B) an element.
C) a heterogeneous mixture.
D) a homogeneous mixture.
88) Apple juice is an example of
A) a compound.
B) an element.
C) a heterogeneous mixture.
D) a homogeneous mixture.
89) Gold is an example of
A) a compound.
B) an element.
C) a heterogeneous mixture.
D) a homogeneous mixture.
90) Carbon dioxide is an example of
A) a compound.
B) an element.
C) a heterogeneous mixture.
D) a homogeneous mixture.
91) Steel is galvanized by giving it a surface coating of zinc. Galvanized steel is an example of
A) a compound.
B) an element.
C) a heterogeneous mixture.
D) a homogeneous mixture.
92) How many electrons are in the ion, Zn2+?
A) 28
B) 30
C) 32
D) 65
93) How many electrons are in the ion, P3-?
A) 12
B) 18
C) 28
D) 34
94) In which of the following sets do all species have the same number of electrons?
A) Br–, Kr, Sr2+
B) C, N3-, O2-
C) Mg2+, Sr2+, Ba2+
D) O, O2-, O2+
95) In which of the following sets do all species have the same number of protons?
A) Br–, Kr, Sr2+
B) C, N3-, O2-
C) Mg2+, Sr2+, Ba2+
D) O, O2-, O2+
96) What is the identity of element Q if the ion Q2+ contains 10 electrons?
A) C
B) O
C) Ne
D) Mg
97) How many electrons are in the ion, CO32-?
A) 16
B) 28
C) 30
D) 32
98) In which set do all elements tend to form cations in binary ionic compounds?
A) Li, B, O
B) Mg, Cr, Pb
C) N, As, Bi
D) O, F, Cl
99) In which set do all elements tend to form anions in binary ionic compounds?
A) C, S, Pb
B) K, Fe, Br
C) Li, Na, K
D) N, O, I