Chemistry Structure and Properties

Nivaldo J. Tro

Chapter 2

Measurement, Problem Solving, and the Mole Concept - all with Video Answers

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Chapter Questions

Problem 1

Explain the relationship between the reliability of a measurement and
the instrument used to make the measurement.

Ronald Prasad

Ronald Prasad

Numerade Educator

Problem 2

What is the significance of the number of digits reported in a measured quantity?

Ronald Prasad

Numerade Educator

Problem 3

Explain the difference between precision and accuracy.

Ahmed Ali

Numerade Educator

Problem 4

Explain the difference between random error and systematic error.

Nicole Smina

Numerade Educator

Problem 5

Explain the difference between density and mass.

Ahmed Ali

Numerade Educator

Problem 6

Explain the difference between intensive and extensive properties.

Mayukh Banik

Numerade Educator

Problem 7

What is energy? Explain the difference between kinetic energy and
potential energy.

David Collins

Numerade Educator

Problem 8

State the law of conservation of energy, and explain its significance.

Ronald Prasad

Numerade Educator

Problem 9

What kind of energy is chemical energy? In what way is an elevated
weight similar to a tank of gasoline?

Qiao Ruan

Numerade Educator

Problem 10

Explain the difference between an exothermic process and an endothermic one.

Ronald Prasad

Numerade Educator

Problem 11

What is dimensional analysis?

Ahmed Ali

Numerade Educator

Problem 12

How should units be treated in calculations?

Kim Trang Nguyen

Kim Trang Nguyen

Numerade Educator

Problem 13

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

Sisi Gao

Numerade Educator

Problem 14

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 15

A ruler used to measure a penny has markings every 1 $\mathrm{mm} .$ Which
measurement for the size of the penny is correctly reported for this
ruler?
$$\begin{array}{llll}{\text { a. } 19.05 \mathrm{mm}} & {\text { b. } 19 \mathrm{mm}} & {\text { c. } 19.1 \mathrm{mm}}\end{array}$$

Dalton Hilovsky

Dalton Hilovsky

Numerade Educator

Problem 16

A scale used to weigh produce at a market has markings every 0.1 $\mathrm{kg}$ .
Which measurement for the mass of a dozen apples is correctly reported for this scale?
$$\begin{array}{llll}{\text { a. } 1.87 \mathrm{kg}} & {\text { b. } 1.9 \mathrm{kg}} & {\text { c. } 1.875 \mathrm{kg}}\end{array}$$

Ronald Prasad

Numerade Educator

Problem 17

Read each measurement to the correct number of significant figures.
Laboratory glassware should always be read from the bottom of the
meniscus.

Qiao Ruan

Numerade Educator

Problem 18

Read each measurement to the correct number of significant figures.
Laboratory glassware should always be read from the bottom of the
meniscus. Digital balances normally display mass to the correct number of significant figures for that particular balance.

Ahmed Ali

Numerade Educator

Problem 19

A new penny has a mass of 2.49 $\mathrm{g}$ and a volume of 0.349 $\mathrm{cm}^{3} .$ Is the
penny made of pure copper? Explain.

Ronald Prasad

Numerade Educator

Problem 20

A titanium bicycle frame displaces 0.314 L of water and has a mass of
1.41 $\mathrm{kg} .$ What is the density of the titanium in $\mathrm{g} / \mathrm{cm}^{3} ?$

Ahmed Ali

Numerade Educator

Problem 21

Glycerol is a syrupy liquid used in cosmetics and soaps. $\mathrm{A} 3.25$ -L sample
of pure glycerol has a mass of $4.10 \times 10^{3} \mathrm{g} .$ What is the density of glycerol in $\mathrm{g} / \mathrm{cm}^{3} ?$

Ronald Prasad

Numerade Educator

Problem 22

An allegedly gold nugget is tested to determine its density. It is found to
displace 19.3 $\mathrm{mL}$ of water and has a mass of 371 $\mathrm{g}$ . Could the nugget be
made of gold?

Ronald Prasad

Numerade Educator

Problem 23

Ethylene glycol (antifreeze) has a density of 1.11 $\mathrm{g} / \mathrm{cm}^{3} .$
a. What is the mass in $g$ of 417 $\mathrm{mL}$ of this liquid?
b. What is the volume in $\mathrm{L}$ of 4.1 $\mathrm{kg}$ of this liquid?

Ronald Prasad

Numerade Educator

Problem 24

Acetone (nail polish remover) has a density of 0.7857 $\mathrm{g} / \mathrm{cm}^{3}$ .
a. What is the mass, in g, of 28.56 $\mathrm{mL}$ of acetone?
b. What is the volume, in mL, of 6.54 g of acetone?

Jennifer Hudspeth

Jennifer Hudspeth

Numerade Educator

Problem 25

A small airplane takes on 245 L of fuel. If the density of the fuel is 0.821
$\mathrm{g} / \mathrm{mL},$ what mass of fuel has the airplane taken on?

Ronald Prasad

Numerade Educator

Problem 26

Human fat has a density of 0.918 $\mathrm{g} / \mathrm{cm}^{3} .$ How much volume ( in $\mathrm{cm}^{3} )$ is
gained by a person who gains 10.0 $\mathrm{lbs}$ of pure fat?

Ronald Prasad

Numerade Educator

Problem 27

Perform each unit conversion.
a. 27.8 $\mathrm{L}$ to $\mathrm{cm}^{3} \quad$ b. 1898 $\mathrm{mg}$ to $\mathrm{kg} \quad$ c. 198 $\mathrm{km}$ to $\mathrm{cm}$

Qiao Ruan

Numerade Educator

Problem 28

Perform each unit conversion.
a. 28.9 nm to $\mu \mathrm{m} \quad$ b. 1432 $\mathrm{cm}^{3}$ to L $\quad$ c. 1211 $\mathrm{Tm}$ to $\mathrm{Gm}$

Ronald Prasad

Numerade Educator

Problem 29

Perform each unit conversion.
$\begin{array}{ll}{\text { a. } 154 \mathrm{cm} \text { to in }} & {\text { b. } 3.14 \mathrm{kg} \text { to g }} \\ {\text { c. } 3.5 \mathrm{L} \text { to } \mathrm{qt}} & {\text { d. } 109 \mathrm{mm} \text { to in }}\end{array}$

Qiao Ruan

Numerade Educator

Problem 30

Perform each unit conversion.
$\begin{array}{ll}{\text { a. } 1.4 \text { in to mm }} & {\text { b. } 116 \text { ft to cm }} \\ {\text { c. } 1845 \text { kg to lb }} & {\text { d. } 815 \text { yd to } k m}\end{array}$

Ronald Prasad

Numerade Educator

Problem 31

A runner wants to run 10.0 $\mathrm{km}$ . She knows that her running pace is 7.5
miles per hour. How many minutes must she run?

Ronald Prasad

Numerade Educator

Problem 32

A cyclist rides at an average speed of 18 miles per hour. If she wants to
bike 212 $\mathrm{km}$ , how long (in hours) must she ride?

Ronald Prasad

Numerade Educator

Problem 33

A European automobile has a gas mileage of 17 $\mathrm{km} / \mathrm{L} .$ What is the
car's gas mileage in miles per gallon?

Ronald Prasad

Numerade Educator

Problem 34

A gas can holds 5.0 gallons of gasoline. Express this quantity in $\mathrm{cm}^{3} .$

Chareen Guzman

Numerade Educator

Problem 35

A house has an area of 195 $\mathrm{m}^{2} .$ What is its area in:
\begin{equation}
\text { a. }\mathrm{km}^{2} \quad \text { b. } \mathrm{dm}^{2} \quad \text { c. } \mathrm{cm}^{2}
\end{equation}

Ronald Prasad

Numerade Educator

Problem 36

A bedroom has a volume of 115 $\mathrm{m}^{3} .$ What is its volume in:
\begin{equation}
\text { a. }\mathrm{km}^{3} \quad \text { b. } \mathrm{dm}^{3} \quad \text { c. } \mathrm{cm}^{3}
\end{equation}

Ronald Prasad

Numerade Educator

Problem 37

The average U.S. farm occupies 435 acres. How many square miles is
this? $(1$ acre $=43,560 \mathrm{ft}^{2}, 1$ mile $=5280 \mathrm{ft})$

Ronald Prasad

Numerade Educator

Problem 38

Total U.S. farmland occupies 954 million acres. How many square
miles is this? $(1$ acre $=43,560 \mathrm{ft}^{2}, 1$ mile $=5280 \mathrm{ft}) .$ Total U.S. land
area is 3.537 million square miles. What percentage of U.S. land is
farmland?

Paul Gabriel

Numerade Educator

Problem 39

An acetaminophen suspension for infants contains 80 $\mathrm{mg} / 0.80 \mathrm{mL}$ suspension. The recommended dose is 15 $\mathrm{mg} / \mathrm{kg}$ body weight. How many
$\mathrm{mL}$ of this suspension should be given to an infant weighing 14 $\mathrm{lbs}$ ?
(Assume two significant figures.)

Ronald Prasad

Numerade Educator

Problem 40

An ibuprofen suspension for infants contains 100 $\mathrm{mg} / 5.0 \mathrm{mL}$ suspension. The recommended dose is 10 $\mathrm{mg} / \mathrm{kg}$ body weight. How many
$\mathrm{mL}$ of this suspension should be given to an infant weighing 18 lbs?
(Assume two significant figures.)

Ronald Prasad

Numerade Educator

Problem 41

Convert between energy units.
$$
\begin{array}{ll}{\text { a. } 534 \mathrm{kWh} \text { to } \mathrm{J}} & {\text { b. } 215 \mathrm{kJ} \text { to Cal }} \\ {\text { c. } 567 \mathrm{Cal} \text { to } \mathrm{J}} & {\text { d. } 2.85 \times 10^{3} \mathrm{J} \text { to cal }}\end{array}
$$

Sisi Gao

Numerade Educator

Problem 42

Convert between energy units.
$$
\begin{array}{ll}{\text { a. } 231 \text { cal to } \mathrm{kJ}} & {\text { b. } 132 \times 10^{4} \mathrm{kJ} \text { to kcal }} \\ {\text { c. } 4.99 \times 10^{3} \mathrm{kJ} \text { to } \mathrm{kWh}} & {\text { d. } 2.88 \times 10^{4} \mathrm{J} \text { to Cal }}\end{array}
$$

Katie Miller

Numerade Educator

Problem 43

Suppose that a person eats 2387 Calories per day. Convert this amount
of energy into each unit.
$$a. J \quad b. kJ \quad c. kWh$$

Sisi Gao

Numerade Educator

Problem 44

A particular frost-free refrigerator uses about 745 $\mathrm{kW}$ h of electrical
energy per vear. Express this amount of energy in each unit.
$$a. J \quad b. kJ \quad c. Cal$$

Ronald Prasad

Numerade Educator

Problem 45

A household receives a $\$ 145$ electricity bill. The cost of electricity is
$\$ 0.120 / \mathrm{k} \mathrm{W}$ h. How much energy, in joules, did the household use?

Ronald Prasad

Numerade Educator

Problem 46

A 150 -lb person burns about 2700 Calories to run a marathon. How
much energy is burned in ky? Assume two significant figures.

David Collins

Numerade Educator

Problem 47

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

Sisi Gao

Numerade Educator

Problem 48

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

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 49

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

Sisi Gao

Numerade Educator

Problem 50

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

Ronald Prasad

Numerade Educator

Problem 51

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

Vasu Makani

Numerade Educator

Problem 52

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

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 53

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

Sisi Gao

Numerade Educator

Problem 54

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

ES

Eugene Schneider

University of Minnesota - Twin Cities

Problem 55

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

Sisi Gao

Numerade Educator

Problem 56

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

Ronald Prasad

Numerade Educator

Problem 57

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

David Collins

Numerade Educator

Problem 58

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 59

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

Sisi Gao

Numerade Educator

Problem 60

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 61

A thief uses a can of sand to replace a solid gold cylinder that sits on a
weight-sensitive, alarmed pedestal. The can of sand and the gold cylinder
have exactly the same dimensions (length $=22 \mathrm{cm}$ and radius $=3.8 \mathrm{cm} ) .$
a. Calculate the mass of each cylinder (ignore the mass of the can itself.. (density of gold $=19.3 \mathrm{g} / \mathrm{cm}^{3}$ , density of sand $=3.00 \mathrm{g} / \mathrm{cm}^{3} )$
b. Did the thief set off the alarm? Explain.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 62

The proton has a radius of approximately $1.0 \times 10^{-13} \mathrm{cm}$ and a mass
of $1.7 \times 10^{-24} \mathrm{g} .$ Determine the density of a proton. For a sphere
$V=(4 / 3) \pi r^{3}$

Ahmed Ali

Numerade Educator

Problem 63

The density of titanium is 4.51 $\mathrm{g} / \mathrm{cm}^{3} .$ What is the volume (in cubic
inches of 3.5 $\mathrm{lbs}$ of titanium?

Ronald Prasad

Numerade Educator

Problem 64

The density of iron is 7.86 $\mathrm{g} / \mathrm{cm}^{3} .$ What is its density in pounds per
cubic inch $\left(1 \mathrm{b} / \mathrm{in}^{3}\right) ?$

Ahmed Ali

Numerade Educator

Problem 65

A steel cylinder has a length of 2.16 in, a radius of 0.22 in, and a mass of
41 g. What is the density of the steel in $\mathrm{g} / \mathrm{cm}^{3}$ ?

Qiao Ruan

Numerade Educator

Problem 66

A solid aluminum sphere has a mass of 85 g. Use the density of aluminum to find the radius of the sphere in inches.

Ronald Prasad

Numerade Educator

Problem 67

A backyard swimming pool holds 185 cu yd $\left(\mathrm{yd}^{3}\right)$ of water. What is the
mass of the water in pounds?

Ankur S

Numerade Educator

Problem 68

An iceberg has a volume of 7655 cu ft. What is the mass of the ice (in
kg composing the iceberg (at $0^{\circ} \mathrm{C} ) ?$

Ronald Prasad

Numerade Educator

Problem 69

The Toyota Prius, a hybrid electric vehicle, has a U.S. Environmental
Protection Agency (EPA) gas mileage rating of 52 mi/gal in the city.
How many kilometers can the Prius travel on 15 of gasoline?

Ronald Prasad

Numerade Educator

Problem 70

The Honda Insight, a hybrid electric vehicle, has an U.S. Environmental
Protection Agency (EPA) gas mileage rating of 57 mi/gal in the city. How many kilometers can the Insight travel on the amount of gasoline that
would fit in a soda can? The volume of a soda can is 355 $\mathrm{mL} .$

Ronald Prasad

Numerade Educator

Problem 71

The single proton that forms the nucleus of the hydrogen atom has a
radius of approximately 1.0 $\times 10^{-13} \mathrm{cm} .$ The hydrogen atom itself has
a radius of approximately 52.9 $\mathrm{pm} .$ What fraction of the space within
the atom is occupied by the nucleus?

Ahmed Ali

Numerade Educator

Problem 72

A sample of gaseous neon atoms at atmospheric pressure and $0^{\circ} \mathrm{C} \mathrm{con}$
tains $2.69 \times 10^{22}$ atoms per liter. The atomic radius of neon is 69 $\mathrm{pm} .$
What fraction of the space is occupied by the atoms themselves? What
does this reveal about the separation between atoms in the gaseous phase?

Ronald Prasad

Numerade Educator

Problem 73

The diameter of a hydrogen atom is 212 pm. Find the length in kilometers of a row of $6.02 \times 10^{23}$ hydrogen atoms. The diameter of a
ping pong ball is 4.0 $\mathrm{cm} .$ Find the length in kilometers of a row of
$6.02 \times 10^{23}$ ping pong balls.

Qiao Ruan

Numerade Educator

Problem 74

The world's record in the $100-\mathrm{m}$ dash is $9.58 \mathrm{s},$ and in the 100 -yd dash
it is 9.07 s. Find the speed in mi/hr of the runners who set these records.

Daphne G. Moore

Daphne G. Moore

Numerade Educator

Problem 75

Table salt contains 39.33 g of sodium per 100 g of salt. The U.S. Food
and Drug Administration (FDA) recommends that adults consume
less than 2.40 of sodium per day. A particular snack mix contains
1.25 g of salt per 100 $\mathrm{g}$ of the mix. What mass of the snack mix can an
adult consume and not exceed the FDA limit?

Ronald Prasad

Numerade Educator

Problem 76

Lead metal can be extracted from a mineral called galena, which contains 86.6$\%$ lead by mass. A particular ore contains 68.5$\%$ galena by
mass. If the lead can be extracted with 92.5$\%$ efficiency, what mass of
ore is required to make a lead sphere with a 5.00 -cm radius?

Ronald Prasad

Numerade Educator

Problem 77

A length of $\# 8$ copper wire (radius $=1.63 \mathrm{mm} )$ has a mass of 24.0 $\mathrm{kg}$
and a resistance of 2.061 ohm per $\mathrm{km}(\Omega / \mathrm{km}) .$ What is the overall resistance of the wire?

Qiao Ruan

Numerade Educator

Problem 78

Rolls of aluminum foil are 304 $\mathrm{mm}$ wide and 0.016 $\mathrm{mm}$ thick. What
maximum length of aluminum foil can be made from 1.10 $\mathrm{kg}$ of
aluminum?

Ronald Prasad

Numerade Educator

Problem 79

Liquid nitrogen has a density of 0.808 $\mathrm{g} / \mathrm{mL}$ and boils at 77 $\mathrm{K}$ . Re-
searchers often purchase liquid nitrogen in insulated $175-\mathrm{L}$ tanks. The
liquid vaporizes quickly to gaseous nitrogen (which has a density of 1.15
$\mathrm{g} / \mathrm{L}$ at room temperature and atmospheric pressure) when the liquid is tank accidentally vaporized in a lab that measured 10.00 $\mathrm{m} \times 10.00 \mathrm{m}$
$\times 2.50 \mathrm{m} .$ What maximum fraction of the air in the room could be displaced by the gaseous nitrogen?

Ronald Prasad

Numerade Educator

Problem 80

Mercury is often used in thermometers. The mercury sits in a bulb on
the bottom of the thermometer and rises up a thin capillary as the temperature rises. Suppose a mercury thermometer contains 3.380 $\mathrm{g}$ of
mercury and has a capillary that is 0.200 $\mathrm{mm}$ in diameter. How far does
the mercury rise in the capillary when the temperature changes from $0.0^{\circ} \mathrm{C}$ to $25.0^{\circ} \mathrm{C}^{2}$ The density of mercury at these temperatures is
13.596 $\mathrm{g} / \mathrm{cm}^{3}$ and 13.534 $\mathrm{g} / \mathrm{cm}^{3}$ , respectively.

Cheryl Glor

Numerade Educator

Problem 81

Carbon-12 contains 6 protons and 6 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.)

Jean Gephart

Numerade Educator

Problem 82

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 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 83

Consider the stack of pennies in problem $82 .$ How much money (in dollars) would this represent? If this money were equally distrributed among
the world's population of 6.5 billion people, how much would each person
receive? Would each person be a millionaire? A billionaire? A tril

Ronald Prasad

Numerade Educator

Problem 84

The mass of an average blueberry is $0.75 \mathrm{g},$ and the mass of an automobile is $2.0 \times 10^{3}$ kg. How many automobiles have the same total combined mass as 1.0 mol blueberries?lionaire?

Ronald Prasad

Numerade Educator

Problem 85

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 86

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 87

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?

Sisi Gao

Numerade Educator

Problem 88

Common brass is a copper and zinc alloy 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?

Ronald Prasad

Numerade Educator

Problem 89

The U.S. Environmental Protection Agency (EPA) sets limits on health-fullevels of air pollutants. The maximum level 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 L.)

Ronald Prasad

Numerade Educator

Problem 90

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

Sisi Gao

Numerade Educator

Problem 91

In 1999 , scientists discovered a new class of black
holes with masses 100 to
$10,000$ times the mass of
our sun that occupy less
space than our moon.
Slack holes has a mass of
$1 \times 10^{3}$ suns and a radio$1 \times 10^{3}$ suns and a radio us equal to one-half the radius of our moon. What is the density of the black hole in $\mathrm{g} / \mathrm{cm}^{3}$ ?
The radius of our sun is $7.0 \times 10^{5} \mathrm{km},$ and it has an average density
of $1.4 \times 10^{3} \mathrm{kg} / \mathrm{m}^{3} .$ The diameter of the moon is $2.16 \times 10^{3}$ miles.

Crystal Wang

Numerade Educator

Problem 92

Polluted air can have carbon monoxide (CO) levels of 15.0 ppm. An average human inhales about 0.50 L of air per breath and takes about 20
breaths per minute. How many milligrams of carbon monoxide dees the average person inhale in an 8 -hour period in this level of carbon monoxide pollution? Assume that the carbon monoxide has a density of 1.2 $\mathrm{g} / \mathrm{L}$ .(Hint: 15.0 ppm CO means 15.0 $\mathrm{L}$ $\mathrm{CO} \operatorname{per} 10^{6} \mathrm{L}$ air. $)$

Ronald Prasad

Numerade Educator

Problem 93

Nanotechnology, the field of building ultrasmall structures one atom at
a time, has progressed in recent years. One potential application of nanotechnology is the construction of artificial cells. The simplest cells
would probably mimic red blood cells, the body's oxygen transporters. Nanocontainers, perhaps constructed of carbon, could be pumped full of
oxygen and injected into a person's bloodstream. If the person needed
additional oxygen - due to a heart attack or for the purpose of space travel, for example - these containers could slowly release oxygen into
the blood, allowing tissues that would otherwise die to remain alive.
Suppose that the nanocontainers were cubic and had an edge length
of 25 nanometers.a. What is the volume of one nanocontainer? ( Ignore the thickness of
the nanocontainer's wall.)
b. Suppose that each nanocontainer could contain pure oxygen pressurized to a density of 85 $\mathrm{g} / \mathrm{L}$ How many grams of oxygen could be
contained by each nanocontainer? c. Air typically contains about 0.28 of oxygen per liter. An average
human inhales about 0.50 L of air per breath and takes about 20
breaths per minute. How many grams of oxygen does a human inhale per hour? (Assume two significant figures.) d. What is the minimum number of nanocontainers that a person
would need in his bloodstream to provide 1 hours worth of oxygen?
e. What is the minimum volume occupied by the number of nanocontainers calculated in part d? Is such a volume feasible, given that
total blood volume in an adult is about 5 $\mathrm{L} ?$

John Incabo

Numerade Educator

Problem 94

Determine the approximate percent increase in waist size that occurs
when a $155-$ -lb person gains 40.0 lbs of fat. Assume that the volume of the person can be modeled by a cylinder that is 4.0 ft tall. The average density of
a human is about $1.0 \mathrm{g} / \mathrm{cm}^{3},$ and the density of fat is 0.918 $\mathrm{g} / \mathrm{cm}^{3} .$

Ronald Prasad

Numerade Educator

Problem 95

A box contains a mixture of small copper spheres and small lead spheres.
The total volume of both metals is measured by the displacement of
water to be 427 $\mathrm{cm}^{3}$ , and the total mass is 4.36 $\mathrm{kg} .$ What percentage of
the spheres is copper?

Ronald Prasad

Numerade Educator

Problem 96

In Section 2.8 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 mm. Texas has a land area of $268,601$ sq mi.

Ronald Prasad

Numerade Educator

Problem 97

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 smaller 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.

Ronald Prasad

Numerade Educator

Problem 98

A cube has an edge length of 7 $\mathrm{cm} .$ If it is divided up into $1-\mathrm{cm}$ cubes,
how many $1-\mathrm{cm}$ cubes are there?

Qiao Ruan

Numerade Educator

Problem 99

Substance $A$ has a density of 1.7 $\mathrm{g} / \mathrm{cm}^{3} .$ Substance $\mathrm{B}$ has a density of
1.7 $\mathrm{kg} / \mathrm{m}^{3} .$ Without doing any calculations, determine which substance is more dense.

Ahmed Ali

Numerade Educator

Problem 100

For each box, examine the blocks attached to the balances. Based on
their positions and sizes, determine which block is more dense (the dark
block or the lighter-colored block), or if the relative densities cannot be
determined. (Think carefully about the information being shown.)

Qiao Ruan

Numerade Educator

Problem 101

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 $\mathrm{C}-12,$ but the amu with respect to $\mathrm{Ne}-20$ ?

Sisi Gao

Numerade Educator

Problem 102

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 $\mathrm{C}-12,$ but the amu with respect to $\mathrm{Ne}-20$ ?
$$55.0 \mathrm{gCr} \quad \text { b. } 45.0 \mathrm{gTi} \quad \text { c. } 60.0 \mathrm{g} \mathrm{Zn}$$

David Collins

Numerade Educator