Chemistry A Molecular Approach

Nivaldo J. Tro

Chapter 2

Atoms and Elements - all with Video Answers

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Chapter Questions

Problem 1

What is Brownian motion? How is it related to the development of the idea that matter is particulate?

David Collins

David Collins

Numerade Educator

Problem 2

Summarize the history of the atomic idea. How was Dalton able to convince others to accept an idea that had been controversial for 2000 years?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 3

State and explain the law of conservation of mass.

Sisi Gao

Numerade Educator

Problem 4

State and explain the law of definite proportions.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 5

State and explain the law of multiple proportions. How is the law of multiple proportions different from the law of definite proportions?

Sisi Gao

Numerade Educator

Problem 6

What are the main ideas in Dalton's atomic theory? How do they help explain the laws of conservation of mass, of constant composition, and of definite proportions?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 7

How and by whom was the electron discovered? What basic properties of the electron were reported with its discovery?

Sisi Gao

Numerade Educator

Problem 8

Explain Millikan's oil drop experiment and how it led to the measurement of the electron's charge. Why is the magnitude of the charge of the electron so important?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 9

Describe the plum-pudding model of the atom.

Sisi Gao

Numerade Educator

Problem 10

Describe Rutherford's gold foil experiment. How did the experiment prove that the plum-pudding model of the atom was wrong?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 11

Describe Rutherford's nuclear model of the atom. What was revolutionary about his model?

Sisi Gao

Numerade Educator

Problem 12

If matter is mostly empty space, as suggested by Rutherford then why does it appear so solid?

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 13

List the three subatomic particles that compose atoms and give the basic properties (mass and charge) of each.

Sisi Gao

Numerade Educator

Problem 14

What defines an element?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 15

Explain the difference between $Z$ (the atomic number) and $A$ (the mass number).

Sisi Gao

Numerade Educator

Problem 16

Where do elements get their names?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 17

What are isotopes? What is percent natural abundance of isotopes?

Sisi Gao

Numerade Educator

Problem 18

Describe the two different notations used to specify isotopes and give an example of each.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 19

What is an ion? A cation? An anion?

Sisi Gao

Numerade Educator

Problem 20

State the periodic law. How did the periodic law lead to the periodic table?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 21

Describe the characteristic properties of metals, nonmetals, and metalloids.

David Collins

Numerade Educator

Problem 22

List the characteristic properties of each group.
$$\begin{array}{ll}{\text { a. noble gases }} & {\text { b. alkali metals }} \\ {\text { c. alkaline earth metals }} & {\text { d. halogens }}\end{array}$$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 23

How do you predict the charges of ions formed by main-group elements?

David Collins

Numerade Educator

Problem 24

What is atomic mass? How is it calculated?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 25

Explain how a mass spectrometer works.

David Collins

Numerade Educator

Problem 26

What kind of information can be determined from a mass spectrum?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 27

What is a mole? How is the mole concept useful in chemical calculations?

Sisi Gao

Numerade Educator

Problem 28

Why is the mass corresponding to a mole of one element different from the mass corresponding to a mole of another element?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 29

A hydrogen-filled balloon is ignited and 1.50 $\mathrm{g}$ of hydrogen is reacted with 12.0 $\mathrm{g}$ of oxygen. How many grams of water vapor form? (Assume that water vapor is the only product.)

David Collins

Numerade Educator

Problem 30

An automobile gasoline tank holds 21 $\mathrm{kg}$ of gasoline. When the gasoline burns, 84 $\mathrm{kg}$ of oxygen is consumed, and carbon dioxide and water are produced. What is the total combined mass of carbon dioxide and water that is produced?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 31

Two samples of carbon tetrachloride are decomposed into their constituent elements. One sample produces 38.9 $\mathrm{g}$ of carbon and 448 $\mathrm{g}$ of chlorine, and the other sample produces 14.8 $\mathrm{g}$ of carbon and 134 $\mathrm{g}$ of chlorine. Are these results consistent with the law of definite proportions? Explain your answer.

David Collins

Numerade Educator

Problem 32

Two samples of sodium chloride are decomposed into their constituent elements. One sample produces 6.98 g of sodium and 10.7 $\mathrm{g}$ of chlorine, and the other sample produces 11.2 $\mathrm{g}$ of sodium and 17.3 $\mathrm{g}$ of chlorine. Are these results consistent with the law of definite proportions? Explain your answer.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 33

The mass ratio of sodium to fluorine in sodium fluoride is $1.21 : 1 .$ A sample of sodium fluoride produces 28.8 $\mathrm{g}$ of sodium upon decomposition. How much fluorine (in grams) forms?

David Collins

Numerade Educator

Problem 34

Upon decomposition, one sample of magnesium fluoride produces 1.65 $\mathrm{kg}$ of magnesium and 2.57 $\mathrm{kg}$ of fluorine. A second sample produces 1.32 $\mathrm{kg}$ of magnesium. How much fluorine (in grams) does the second sample produce?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 35

Two different compounds containing osmium and oxygen have the following masses of oxygen per gram of osmium: 0.168 and 0.3369 $\mathrm{g} .$ Show that these amounts are consistent with the law
of multiple proportions.

Sisi Gao

Numerade Educator

Problem 36

Palladium forms three different compounds with sulfur. The mass of sulfur per gram of palladium in each compound is listed here. Show that these masses are consistent with the law of multiple proportions.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 37

Sulfur and oxygen form both sulfur dioxide and sulfur trioxide. When samples of these are decomposed, the sulfur dioxide produces 3.49 goxygen and 3.50 g sulfur, while the sulfur trioxide produces 6.75 g oxygen and 4.50 sulfur. Calculate the mass of oxygen per gram of sulfur for each sample and show that
these results are consistent with the law of multiple proportions.

David Collins

Numerade Educator

Problem 38

Sulfur and fluorine form several different compounds including sulfur hexafluoride and sulfur tetrafluoride. Decomposition of a sample of sulfur hexafluoride produces 4.45 g of fluorine and 1.25 $\mathrm{g}$ of sulfur, while decomposition of a sample of sulfur tetrafluoride produces 4.43 g of fluorine and 1.87 g of sulfur. Calculate the mass of fluorine per gram of sulfur for each sample and show that these results are consistent with the law of multiple proportions.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 39

Which statements are consistent with Dalton's atomic theory as it was originally stated? Why?
a. Sulfur and oxygen atoms have the same mass.
b. All cobalt atoms are identical.
c. Potassium and chlorine atoms combine in a $1 : 1$ ratio to form potassium chloride.
d. Lead atoms can be converted into gold.

GL

Gracy Lin

Numerade Educator

Problem 40

Which statements are inconsistent with Dalton's atomic theory as it was originally stated? Why?
a. All carbon atoms are identical.
b. An oxygen atom combines with 1.5 hydrogen atoms to form a water molecule.
c. Two oxygen atoms combine with a carbon atom to form a carbon dioxide molecule.
d. The formation of a compound often involves the destruction of one or more atoms.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 41

Which statements are consistent with Rutherford's nuclear theory as it was originally stated? Why?
a. The volume of an atom is mostly empty space.
b. The nucleus of an atom is small compared to the size of the atom.
c. Neutral lithium atoms contain more neutrons than protons.
d. Neutral lithium atoms contain more protons than electrons.

Rabia Shuaib

Numerade Educator

Problem 42

Which statements are inconsistent with Rutherford's nuclear theory as it was originally stated? Why?
a. since electrons are smaller than protons, and since a hydrogen atom contains only one proton and one electron, it must follow that the volume of a hydrogen atom is mostly due to the proton.
b. A nitrogen atom has seven protons in its nucleus and seven electrons outside of its nucleus.
c. A phosphorus atom has 15 protons in its nucleus and 150 electrons outside of its nucleus.
d. The majority of the mass of a fluorine atom is due to its nine electrons.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 43

A chemist in an imaginary universe, where electrons have a different charge than they do in our universe, performs the Millikan oil drop experiment to measure the electron's charge. The charges of several drops are recorded here. What is the charge of the electron in this imaginary universe?

EC

Eric Chang

Numerade Educator

Problem 44

Imagine a unit of charge called the zorg. A chemist performs the oil drop experiment and measures the charge of each drop in zorgs. Based on the results shown here, what is the charge of the electron in zorgs $(z) ?$ How many electrons are in each drop?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 45

On a dry day, your body can accumulate static charge from walking across a carpet or from brushing your hair. If your body develops a charge of $-15 \mu C$ (microcoulombs), how many excess electrons has it acquired? What is their collective mass?

David Collins

Numerade Educator

Problem 46

How many electrons are necessary to produce a charge of $-1.0 \mathrm{C}$ ? What is the mass of this many electrons?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 47

Which statements about subatomic particles are true?
a. If an atom has an equal number of protons and electrons, it will be charge-neutral.
b. Electrons are attracted to protons.
c. Electrons are much lighter than neutrons.
d. Protons have twice the mass of neutrons.

Sisi Gao

Numerade Educator

Problem 48

Which statements about subatomic particles are false?
a. Protons and electrons have charges of the same magnitude but opposite signs.
b. Protons have about the same mass as neutrons.
c. Some atoms don't have any protons.
d. Protons and neutrons have charges of the same magnitude but opposite signs.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 49

How many electrons does it take to equal the mass of a proton?

David Collins

Numerade Educator

Problem 50

A helium nucleus has two protons and two neutrons. How many electrons does it take to equal the mass of a helium nucleus?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 51

Write isotopic symbols in the form $X-A$ (e.g., $C-13 )$ for each isotope.
a. the silver isotope with 60 neutrons
b. the silver isotope with 62 neutrons
c. the uranium isotope with 146 neutrons
d. the hydrogen isotope with one neutron

David Collins

Numerade Educator

Problem 52

Write isotopic symbols in the form $_{2}^{4} X$ for each isotope.
a. the copper isotope with 34 neutrons
b. the copper isotope with 36 neutrons
c. the potassium isotope with 21 neutrons
d. the argon isotope with 22 neutrons

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 53

Determine the number of protons and the number of neutrons in each isotope.
a. 1$\frac{14}{7} \mathrm{N}$ b. $\frac{23}{11} \mathrm{Na}$ c. $\frac{222}{86} \mathrm{Rn}$ d. $\frac{208}{82} \mathrm{Pb}$

David Collins

Numerade Educator

Problem 54

Determine the number of protons and the number of neutrons in each isotope.
a. $\frac{40}{19} \mathrm{K}$ b. $\frac{226}{85} \mathrm{Ra}$ c. $\frac{99}{43} \mathrm{Tc}$ d. $\frac{33}{15} \mathrm{P}$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 55

The amount of carbon-14 in ancient artifacts and fossils is often used to establish their age. Determine the number of protons and the number of neutrons in carbon-14 and write its symbol in the form $\frac{4}{2} \mathrm{X}$ .

David Collins

Numerade Educator

Problem 56

Uranium-235 is used in nuclear fission. Determine the number of protons and the number of neutrons in uranium-235 and write its symbol in the form $\frac{4}{2} X$ .

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 57

Determine the number of protons and the number of electrons in each ion.
$$\text { a. }\mathrm{Ni}^{2+} \quad \text { b. } \mathrm{s}^{2-} \quad \text { c. Br }^{-} \quad \text { d. } \mathrm{Cr}^{3+}$$

David Collins

Numerade Educator

Problem 58

Determine the number of protons and the number of electrons in each ion.
$$\text { a. }\mathrm{Al}^{3+} \quad \text { b. } \mathrm{Se}^{2-} \quad \text { c. } \mathrm{Ga}^{3+} \quad \text { d. } \mathrm{Sr}^{2+}$$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 59

Predict the charge of the ion formed by each element.
$$a. o \quad b. \mathrm{k} \quad c. Al \quad d. Rb$$

David Collins

Numerade Educator

Problem 60

Predict the charge of the ion formed by each element.
$$a. \mathrm{Mg} \quad b. \mathrm{N} \quad c. \mathrm{F} \quad d. Na$$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 61

Fill in the blanks to complete the table.

Sisi Gao

Numerade Educator

Problem 62

Fill in the blanks to complete the table.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 63

Write the name of each element and classify it as a metal, nonmetal, or metalloid.
$$a. K \quad b. Ba \quad c. 1\quad d. 0\quad e. Sb$$

David Collins

Numerade Educator

Problem 64

Write the symbol for each element and classify it as a metal, nonmetal, or metalloid.
$$\begin{array}{l}{\text { a. gold }} \\ {\text { b. fluorine }} \\ {\text { c. sodium }} \\ {\text { d. tin }} \\ {\text { e. argon }}\end{array}$$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 65

Determine whether or not each element is a main-group element.
$$\begin{array}{l}{\text { a. tellurium }} \\ {\text { b. potassium }} \\ {\text { c. vanadium }} \\ {\text { d. manganese }}\end{array}$$

David Collins

Numerade Educator

Problem 66

Determine whether or not each element is a transition element.
$$\begin{array}{l}{\text { a. Cr }} \\ {\text { b. Br }} \\ {\text { c. Mo }} \\ {\text { d. Cs }}\end{array}$$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 67

Classify each element as an alkali metal, alkaline earth metal, halogen, or noble gas.
$$\begin{array}{l}{\text { a. sodium }} \\ {\text { b. iodine }} \\ {\text { c. calcium }} \\ {\text { d. barium }} \\ {\text { e. krypton }}\end{array}$$

David Collins

Numerade Educator

Problem 68

Classify each element as an alkali metal, alkaline earth metal, halogen, or noble gas.
$$\begin{array}{l}{\text { a. } \mathrm{F}} \\ {\text { b. Sr }} \\ {\text { c. } \mathrm{K}} \\ {\text { d. Ne }} \\ {\text { e. At }}\end{array}$$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 69

Which pair of elements do you expect to be most similar? Why?
$$\begin{array}{l}{\text { a. } \mathrm{Nand} \mathrm{Ni}} \\ {\text { b. Mo and } \mathrm{Sn}} \\ {\text { c. Na and } \mathrm{Mg}} \\ {\text { d. Cland } \mathrm{F}} \\ {\text { e. Si and P }}\end{array}$$

Sisi Gao

Numerade Educator

Problem 70

Which pair of elements do you expect to be most similar? Why?
$$\begin{array}{l}{\text { a. nitrogen and oxygen }} \\ {\text { b. titanium and gallium }} \\ {\text { c. lithium and sodium }} \\ {\text { d. germanium and arsenic }} \\ {\text { e. argon and bromine }}\end{array}$$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 71

Gallium has two naturally occurring isotopes with the following masses and natural abundances:
Sketch the mass spectrum of gallium.

David Collins

Numerade Educator

Problem 72

Magnesium has three naturally occurring isotopes with the following masses and natural abundances:
Sketch the mass spectrum of magnesium.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 73

The atomic mass of fluorine is 18.998 amu, and its mass spectrum shows a large peak at this mass. The atomic mass of chlorine is 35.45 amu, yet the mass spectrum of chlorine does not show a peak at this mass. Explain the difference.

Sisi Gao

Numerade Educator

Problem 74

The atomic mass of copper is 63.546 amu. Do any copper isotopes have a mass of 63.546 amu? Explain.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 75

An element has two naturally occurring isotopes. Isotope 1 has a mass of 120.9038 amu and a relative abundance of $57.4 \%,$ and isotope 2 has a mass of 122.9042 amu. Find the atomic mass of this element and identify it.

David Collins

Numerade Educator

Problem 76

An element has four naturally occurring isotopes with the masses and natural abundances given here. Find the atomic mass of the element and identify it.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 77

Bromine has two naturally occurring isotopes (Br- 79 and Br-81) and has an atomic mass of 79.904 amu. The mass of Br-s1 is 80.9163 amu, and its natural abundance is 49.31$\%$ . Calculate the mass and natural abundance of Br- $79 .$

Sisi Gao

Numerade Educator

Problem 78

Silicon has three naturally occurring isotopes $(\mathrm{si}-28, \mathrm{si}-29,$ and $\mathrm{Si}-30$ ). The mass and natural abundance of $\$ \mathrm{i}-28$ are 27.9769 amu and 92.2$\%$ , respectivelv. The mass and natural abundance of Si-29 are 28.9765 amu and 4.67$\%$ , respectively. Find the mass and natural abundance of $S_{1-30} .$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 79

Use the mass spectrum of europium to determine the atomic mass of europium.

Prashant Bana

Numerade Educator

Problem 80

Use the mass spectrum of rubidium to determine the atomic mass of rubidium.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 81

How many sulfur atoms are there in 5.52 mol of sulfur?

Sisi Gao

Numerade Educator

Problem 82

How many moles of aluminum do $3.7 \times 10^{24}$ aluminum atoms represent?

Chareen Guzman

Numerade Educator

Problem 83

What is the amount, in moles, of each elemental sample?
$$\begin{array}{ll}{\text { a. } 11.8 \mathrm{g} \text { Ar }} & {\text { b. } 3.55 \mathrm{g} \mathrm{Zn}} \\ {\text { c. } 26.1 \mathrm{g} \mathrm{Ta}} & {\text { d. } 0.211 \mathrm{g} \mathrm{Li}}\end{array}$$

David Collins

Numerade Educator

Problem 84

What is the mass, in grams, of each elemental sample?
$$\begin{array}{l}{\text { a. } 2.3 \times 10^{-3} \text { mol Sb }} \\ {\text { b. } 0.0355 \text { mol Ba }} \\ {\text { c. } 43.9 \text { mol Xe }} \\ {\text { d. } 1.3 \text { mol } W}\end{array}$$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 85

How many silver atoms are there in 3.78 g of silver?

Sisi Gao

Numerade Educator

Problem 86

What is the mass of $4.91 \times 10^{21}$ platinum atoms?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 87

Calculate the number of atoms in each sample.
$$\begin{array}{ll}{\text { a. } 5.18 \mathrm{g} \mathrm{P}} & {\text { b. } 2.26 \mathrm{g} \mathrm{Hg}} \\ {\text { c. } 1.87 \mathrm{g} \mathrm{Bi}} & {\text { d. } 0.082 \mathrm{gr}}\end{array}$$

David Collins

Numerade Educator

Problem 88

Calculate the number of atoms in each sample.
$$\begin{array}{ll}{\text { a. } 14.955 \mathrm{gCr}} & {\text { b. } 39.733 \mathrm{gS}} \\ {\text { c. } 12.899 \mathrm{gPt}} & {\text { d. } 97.552 \mathrm{g} \mathrm{Sn}}\end{array}$$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 89

Calculate the mass, in grams, of each sample.
$$\begin{array}{l}{\text { a. } 1.1 \times 10^{23} \text { gold atoms }} \\ {\text { b. } 2.82 \times 10^{22} \text { helium atoms }} \\ {\text { c. } 1.8 \times 10^{23} \text { lead atoms }} \\ {\text { d. } 7.9 \times 10^{21} \text { uranium atoms }}\end{array}$$

David Collins

Numerade Educator

Problem 90

Calculate the mass, in $\mathrm{kg},$ of each sample.
$$\begin{array}{l}{\text { a. } 7.55 \times 10^{26} \text { cadmium atoms }} \\ {\text { b. } 8.15 \times 10^{27} \text { nickel atoms }} \\ {\text { c. } 1.22 \times 10^{27} \text { manganese atoms }} \\ {\text { d. } 5.48 \times 10^{29} \text { lithium atoms }}\end{array}$$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 91

How many carbon atoms are there in a diamond (pure carbon)
with a mass of 52 $\mathrm{mg}$ ?

Sisi Gao

Numerade Educator

Problem 92

How many helium atoms are there in a helium blimp containing 536 $\mathrm{kg}$ of helium?

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 93

Calculate the average mass, in grams, of one platinum atom.

Sisi Gao

Numerade Educator

Problem 94

Using scanning tunneling microscopy, scientists at IBM wrote the initials of their company with 35 individual xenon atoms (as shown below). Calculate the total mass of these letters in grams.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 95

A 7.83 g sample of $\mathrm{HCN}$ contains 0.290 $\mathrm{g}$ of $\mathrm{H}$ and 4.06 $\mathrm{g}$ of $\mathrm{N}$ . Find the mass of carbon in a sample of HCN with a mass of 3.37 $\mathrm{g}$ .

Sisi Gao

Numerade Educator

Problem 96

The ratio of sulfur to oxygen by mass in $\mathrm{SO}_{2}$ is $1.0 : 1.0 .$
a. Find the ratio of sulfur to oxygen by mass in $\mathrm{SO}_{3}$ .
b. Find the ratio of sulfur to oxygen by mass in $\mathrm{S}_{2} \mathrm{O}$ .

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 97

The ratio of oxygen to carbon by mass in carbon monoxide is $1.33 : 1.00$ . Find the formula of an oxide of carbon in which the ratio by mass of oxygen to carbon is $2.00 : 1.00$ .

David Collins

Numerade Educator

Problem 98

The ratio of the mass of a nitrogen atom to the mass of an atom of $^{12} \mathrm{C}$ is 7$\cdot 6$ , and the ratio of the mass of nitrogen to oxygen in $\mathrm{N}_{2} \mathrm{O}$ is $7 : 4$ . Find the mass of 1 $\mathrm{mol}$ of oxygen atoms.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 99

An $\alpha$ particle, $4 \mathrm{e}^{2+},$ has a mass of 4.00151 amu. Find the value of its charge-to-mass ratio in $\mathrm{C} / \mathrm{kg}$ .

David Collins

Numerade Educator

Problem 100

Naturally occurring iodine has an atomic mass of 126.9045 amu. A 12.3849 g sample of iodine is accidentally contaminated with an additional 1.00070 gof $^{129} 1,$ a synthetic radioisotope of iodine used in the treatment of certain diseases of the thyroid gland. The mass of 129 I is 128.9050 amu. Find the apparent "atomic mass" of the contaminated iodine.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 101

Use the mass spectrum of lead to estimate the atomic mass of lead. Estimate the mass and percent intensity values from the graph to three significant figures.

A. Elizabeth Hildreth

A. Elizabeth Hildreth

Numerade Educator

Problem 102

Use the mass spectrum of mercury to estimate the atomic mass of mercury. Estimate the masses and percent intensity values from the graph to three significant figures.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 103

Nuclei with the same number of neutrons but different mass numbers are called isotones. Write the symbols of four isotones of $^{266} \mathrm{Th} .$

David Collins

Numerade Educator

Problem 104

Fill in the blanks to complete the table.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 105

Fill in the blanks to complete the table.

Sisi Gao

Numerade Educator

Problem 106

Neutron stars are composed of solid nuclear matter, primarily neutrons. Assume the radius of a neutron is approximately $1.0 \times 10^{-13} \mathrm{cm}$ . Calculate the density of a neutron. [Hint: For a
sphere $V=(4 / 3) \pi r^{3} . ]$ Assuming that a neutron star has the same density as a neutron, calculate the mass (in kg) of a small piece of a neutron star the size of a spherical pebble with a radius of 0.10 $\mathrm{mm}$ .

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 107

Carbon-12 contains six protons and six neutrons. The radius of the nucleus is approximately 2.7 fm (femtometers) and the radius of the atom is approximately 70 pm (picometers). Calculate the volume of the nucleus and the volume of the atom. What percentage of the carbon atom's volume is occupied by the nucleus? (Assume two significant figures.)

David Collins

Numerade Educator

Problem 108

A penny has a thickness of approximately 1.0 $\mathrm{mm}$ . If you stacked Avogadro's number of pennies one on top of the other on Earth's surface, how far would the stack extend (in $\mathrm{km} ) ?$ [For comparison, the sun is about 150 million km from Earth and the nearest star (Proxima Centauri) is about 40 trillion km from Earth.]

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 109

Consider the stack of pennies in the previous problem. How much money (in dollars) would this represent? If this money were equally distributed among the world's population of 7.0 billion
people, how much would each person receive? Would each person be a millionaire? A billionaire? A trillionaire?

David Collins

Numerade Educator

Problem 110

The mass of an average blueberry is 0.75 $\mathrm{g}$ and the mass of an automobile is $2.0 \times 10^{3} \mathrm{kg}$ . Find the number of automobiles whose total mass is the same as 1.0 mol of blueberries.

Ronald Prasad

Numerade Educator

Problem 111

Suppose that atomic masses were based on the assignment of a mass of 12.000 $\mathrm{g}$ to 1 $\mathrm{mol}$ of carbon, rather than 1 $\mathrm{mol}$ of 12 $\mathrm{C}$ What would the atomic mass of oxygen be? (The atomic masses of carbon and oxygen based on the assignment of 12.000 g to
1 mol of $^{12} \mathrm{C}$ are 12.011 amu and 15.9994 amu, respectively.)

David Collins

Numerade Educator

Problem 112

A pure titanium cube has an edge length of 2.78 in. How many titanium atoms does it contain? Titanium has a density of 4.50 $\mathrm{g} / \mathrm{cm}^{3} .$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 113

A pure copper sphere has a radius of 0.935 in. How many copper atoms does it contain? [The volume of a sphere is $(4 / 3) \pi r^{3}$ and the density of copper is 8.96 $\mathrm{g} / \mathrm{cm}^{3} . ]$

Sisi Gao

Numerade Educator

Problem 114

What is the radius (in $\mathrm{cm}$ ) of a pure copper sphere that contains $1.14 \times 10^{24}$ copper atoms? [The volume of a sphere is $(4 / 3) \pi r^{3}$ and the density of copper is 8.96 $\mathrm{g} / \mathrm{cm}^{3} . ]$

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 115

What is the edge length (in $\mathrm{cm} )$ of a titanium cube that contains $2.55 \times 10^{24}$ titanium atoms? The density of titanium is 4.50 $\mathrm{g} / \mathrm{cm}^{3} .$

David Collins

Numerade Educator

Problem 116

Boron has only two naturally occurring isotopes. The mass of boron-10 is 10.01294 amu and the mass of boron-11 is 11.00931 amu. Calculate the relative abundances of the two isotopes.

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 117

Lithium has only two naturally occurring isotopes. The mass of lithium-6 is 6.01512 amu and the mass of lithium-7 is 7.01601 amu. Calculate the relative abundances of the two isotopes.

David Collins

Numerade Educator

Problem 118

Common brass is a copper and zincalloy containing 37.0$\%$ zinc by mass and having a density of 8.48 $\mathrm{g} / \mathrm{cm}^{3} .$ A fitting composed of common brass has a total volume of 112.5 $\mathrm{cm}^{3} .$ How many atoms (copper and zinc) does the fitting contain?

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Eugene Schneider

University of Minnesota - Twin Cities

Problem 119

A 67.2 g sample of a gold and palladium alloy contains $2.49 \times 10^{23}$ atoms. What is the composition (by mass) of the alloy?

David Collins

Numerade Educator

Problem 120

Naturally occurring chlorine is composed of two isotopes: 75.76$\%$ Cl-35 (mass 34.9688 amu) and 24.24$\%$ Cl-37 (mass 36.9659 amu $)$ . Naturally occurring oxygen is composed of three isotopes: 99.757$\%$ O-16 (mass 15.9949 amu), 0.038$\%$ O-17 (mass 16.9991 amu), and 0.205$\%$ O-18 (mass 17.9991 amu). The compound dichlorine monoxide is composed of two chlorine atoms and one oxygen atom bonded together to form the Cl $_{2} \mathrm{O}$ molecule. How many $\mathrm{Cl}_{2} \mathrm{O}$ molecules of different masses naturally exist? Give the masses of the three most abundant $\mathrm{Cl}_{2} \mathrm{O}$
molecules.

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Eugene Schneider

University of Minnesota - Twin Cities

Problem 121

Silver is composed of two naturally occurring isotopes: $A g-107$ $(51.83996)$ and $A g-109 .$ The ratio of the masses of the two isotopes is 1.0187 . What is the mass of $A g-107 ?$

David Collins

Numerade Educator

Problem 122

The U.S. Environmental Protection Agency (EPA) sets limits on healthful levels of air pollutants. The maximum level that the EPA considers safe for lead air pollution is 1.5$\mu g / m^{3} .$ If your lungs were filled with air containing this level of lead, how many lead atoms would be in your lungs? (Assume a total lung volume of 5.50 $\mathrm{L}$ )

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Eugene Schneider

University of Minnesota - Twin Cities

Problem 123

Pure gold is usually too soft for jewelry, so it is often alloyed with other metals. How many gold atoms are in an 0.255 - ounce, 18 $\mathrm{K}$ gold bracelet? (18 K gold is 75$\%$ gold by mass.)

David Collins

Numerade Educator

Problem 124

In Section $2.9,$ it was stated that 1 mol of sand grains would cover the state of Texas to several feet. Estimate how many feet by assuming that the sand grains are roughly cube-shaped, each one with an edge length of 0.10 $\mathrm{mm} .$ Texas a land area of 268.601 square miles.

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Eugene Schneider

University of Minnesota - Twin Cities

Problem 125

Use the concepts in this chapter to obtain an estimate for the number of atoms in the universe. Make the following assumptions: (a) All of the atoms in the universe are hydrogen atoms in stars. (This is not a ridiculous assumption because over three-fourths of the atoms in the universe are in fact hydrogen. Gas and dust between the stars represent only about 15$\%$ of the visible matter of our galaxy, and planets compose a far tinier fraction.) (b) The sun is a typical star composed of pure hydrogen with a density of 1.4 $\mathrm{g} / \mathrm{cm}^{3}$ and a radius of $7 \times 10^{8} \mathrm{m}$ . (c) Each of the roughly 100 billion stars in the Milky Way galaxy contains the same number of atoms as our sun. (d) Each of the 10 billion galaxies in the visible universe contains the same number of atoms as our Milky Way galaxy.

Rashmi Sinha

Numerade Educator

Problem 126

On the previous page is a representation of 50 atoms of a fictitious element called westmontium (Wt). The red spheres represent $W t-296,$ the blue spheres $W t-297,$ and the green spheres $W t-298 .$
a. Assuming that the sample is statistically representative of a naturally occurring sample, calculate the percent natural abundance of each Wt isotope.
b. Draw the mass spectrum for a naturally occurring sample of Wt.
c. The mass of each $\mathrm{Wt}$ isotope is measured relative to C-12 and tabulated. Use the mass of $\mathrm{C}-12$ to convert each of the masses to amu and calculate the atomic mass of $\mathrm{Wt}$ .

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Eugene Schneider

University of Minnesota - Twin Cities

Problem 127

The ratio of oxygen to nitrogen by mass in $\mathrm{NO}_{2}$ is 2.29 . The ratio of fluorine to nitrogen by mass in $\mathrm{NF}_{3}$ is 4.07 . Find the ratio of oxygen to fluorine by mass in $\mathrm{OF}_{2}$ .

David Collins

Numerade Educator

Problem 128

Naturally occurring cobalt consists of only one isotope, s9 $\mathrm{Co}$ , whose relative atomic mass is $58.9332 .$ A synthetic radioactive isotope of cobalt, $^{60} \mathrm{Co},$ has a relative atomic mass of 59.9338 and is used in radiation therapy for cancer. $\mathrm{A} 1.5886 \mathrm{g}$ sample of cobalt has an apparent "atomic mass" of $58.9901 .$ Find the mass of $^{60} \mathrm{Co}$ in this sample.

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Eugene Schneider

University of Minnesota - Twin Cities

Problem 129

A 7.36 $\mathrm{g}$ sample of copper is contaminated with an additional 0.51 $\mathrm{g}$ of zinc. Suppose an atomic mass measurement was performed on this sample. What would be the measured atomic mass?

Ernest Williams

Ernest Williams

Numerade Educator

Problem 130

The ratio of the mass of $O$ to the mass of $N$ in $N_{2} O_{3}$ is $12 : 7 .$ Another binary compound of nitrogen has a ratio of $O$ to $N$ of $16 : 7$ What is its formula? What is the ratio of $O$ to $N$ in the next member of this series of compounds?

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Eugene Schneider

University of Minnesota - Twin Cities

Problem 131

Naturally occurring magnesium has an atomic mass of 24.312 and consists of three isotopes. The major isotope is $^{24} \mathrm{Mg}$ , natural abundance $78.9996,$ relative atomic mass $23.98504 .$ The next most abundant isotope is $^{26} \mathrm{Mg}$ , relative atomic mass $25.98259 .$ The third most abundant isotope is 25 $\mathrm{Mg}$ , whose natural abundance is in the ratio of 0.9083 to that of $^{26} \mathrm{Mg}$ . Find the relative atomic mass of $^{25} \mathrm{Mg}$ .

David Collins

Numerade Educator

Problem 132

Which answer is an example of the law of multiple proportions? Explain.
a. Two different samples of water are found to have the sameratio of hydrogen to oxygen.
b. When hydrogen and oxygen react, the mass of water formedis exactly equal to the mass of hydrogen and oxygen that reacted.
c. The mass ratio of oxygen to hydrogen in water is $8 : 1 .$ The mass ratio of oxygen to hydrogen in hydrogen peroxide (acompound that only contains hydrogen and oxygen) is $16 : 1$

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Eugene Schneider

University of Minnesota - Twin Cities

Problem 133

Lithium has two naturally occurring isotopes: Li-6 (natural abundance 7.5$\%$ ) and Li-7 (natural abundance 92.5$\%$ ). Using circles to represent protons and squares to represent neutrons,
draw the nucleus of each isotope. How many Li-6 atoms are present, on average, in a 1000 -atom sample of lithium?

David Collins

Numerade Educator

Problem 134

As we saw in the previous problem, lithium has two naturally occurring isotopes: Li-6 (natural abundance 7.5$\%$ ; mass 6.0151 amu) and $L \mathbf{i}-7$ (natural abundance 92.5$\%$ ; mass 7.0160 amul. Without doing any calculations, determine which mass is closest to the atomic mass of Li.
$$\text { a. }6.00 \text { amu } \quad \text { b. } 6.50 \text { amu } \quad \text { c. } 7.00$$

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Eugene Schneider

University of Minnesota - Twin Cities

Problem 135

The mole is defined as the amount of a substance containing the same number of particles as exactly 12 $\mathrm{g}$ of $\mathrm{C}-12 .$ The amu is defined as 1$/ 12$ of the mass of an atom of $\mathrm{C}-12 .$ Why is it important that both of these definitions reference the same isotope? What would be the result, for example, of defining the mole with respect to $C-12,$ but the amu with respect to Ne- 20$?$

David Collins

Numerade Educator

Problem 136

Without doing any calculations, determine which of the samples contains the greatest amount of the element in moles. Which contains the greatest mass of the element?
$$\text { a. }55.0 \mathrm{gCr} \quad \text { b. } 45.0 \mathrm{g} \text { Ti } \quad \text { c. } 60.0 \mathrm{g} \mathrm{Zn}$$

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Eugene Schneider

University of Minnesota - Twin Cities

Problem 137

The atomic radii of the isotopes of an element are identical to one another. However, the atomic radii of the ions of an element are significantly different from the atomic radii of the neutral atom of the element. Explain.

David Collins

Numerade Educator

Problem 138

The table shown here includes data similar to those used by Mendeleev when he created the periodic table. On a small card, write the symbol, atomic mass, and a stable compound formed by each element. Without consulting a periodic table, arrange the cards so that atomic mass increases from left to right and elements with similar properties are above and below each other. Copy the periodic table you have invented onto a piece of paper. There is one element missing. Predict its mass and a stable compound it might form.

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Eugene Schneider

University of Minnesota - Twin Cities

Problem 139

In a naturally occurring sample, 19.8$\%$ of boron atoms have five neutrons and 80.2$\%$ have six neutrons. What is the mass number of each boron isotope? Sketch a sample of 10 atoms that is nearly representative of a natural sample. What is the average mass of the atoms in your drawing? What is the atomic mass of boron? (Boron-10 has a mass of 10.01294 amu and boron-11 has a mass of 11.00931 amu.)

David Collins

Numerade Educator

Problem 140

In complete sentences, describe the similarities and differences between:
a. different isotopes of an element
b. a neutral atom and an ion of the same element

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Eugene Schneider

University of Minnesota - Twin Cities

Problem 141

Calculate the mass in grams of one mole of each of the following (the mass of a single item is given in parentheses): electrons $\left(9.10938 \times 10^{-28} \mathrm{g}\right),$ protons $\left(1.67262 \times 10^{-24} \mathrm{g}\right),$ neutrons $\left(1.67493 \times 10^{-24} \mathrm{g}\right),$ atoms of carbon-12 $\left(1.992646 \times 10^{-23} \mathrm{g}\right)$ and doughnuts $(74$ g). Compare the mass of one mole of carbon-12 atoms to the sum of the masses of the particles that it contains. If the doughnut mentioned in this question were made entirely of carbon, how many atoms would it contain?

David Collins

Numerade Educator

Problem 142

Demand for recycled paper has increased as consumers have become more aware of the environmental issues surrounding waste disposal. Paper is a natural raw material made from renewable wood and plants. Recycled paper is made from waste paper and paperboard. Both new paper and recycled paper contain traces of heavy metals. However, some types of recycled paper contain more heavy metals than new paper due, in part, to the inks used for printing or adding color to the original paper. Metals can migrate from the paper packaging and containers used for food to the food itself. This metal migration is controlled and monitored to reduce the exposure of humans to heavy metals. Food agencies in each country determine the limit of cadmium, zinc, nickel, and copper in packaging materials. Most countries impose a limit of heavy metals in recycled paper not to exceed 100.0 ppm or 100.0 $\mathrm{mg} / \mathrm{kg}$ . The limit for lead in eggfruit, or vegetable-packaging is lower-not to exceed-20.0 mg/kg. The table in Figure a $\nabla$ lists the results of the analysis of samples of recycled paper produced by a manufacturer during a three-month period. The goal of the manufacturer is to reduce the amount of heavy metals-especially lead-in the recycled paper it produces and sells. From March to May, the manufacturer varied the
methods of production each month to determine which method would produce paper with the lowest metal content. Each month, lab technicians cut small samples of recycled paper with an area of 1.000 $\mathrm{dm}^{2}$ and a thickness of 0.0500 $\mathrm{cm} .$ The technicians then prepared the samples for analysis. The average density of the samples is $800.0 \pm 0.0245 \mathrm{kg} / \mathrm{m}^{3} .$ Use the information provided in the figure to answer the
following questions:
a. Did the company reduce the amount of lead in its product between March and May?
b. Which metal was not reduced?
c. Each month's sample represents a different manufacturing process. Which process would you recommend the manufacturer choose to continue to use over the next year while additional processes are tested? Why?
d. What is the total amount of the five metals for the April sample (in mg/kg)?
e. What is the total mass (in mg) of the five metals for the April sample found in the 1.000 $\mathrm{dm}^{2} \times 0.0500 \mathrm{cm}$ sample?
f. Lead has four stable isotopes: 204 $\mathrm{Pb}$ $^{206} \mathrm{Pb}_{,}^{207} \mathrm{Pb},^{208} \mathrm{Pb}$ with 96 abundances of $1.40,24.10,22.10,$ and $52.40,$ respectively.Determine the mass (in mg) of $^{208} \mathrm{Pb}$ in the April sample.
g. Sketch the mass spectrum for lead.

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Eugene Schneider

University of Minnesota - Twin Cities