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Chemistry

Julia Burdge

Chapter 3

Stoichiometry: Ratios of Combination - all with Video Answers

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Chapter Questions

01:10

Problem 1

What is meant by the term molecular mass, and why is the molecular mass that we calculate generally an average molecular mass?

Daniel Kim
Daniel Kim
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01:05

Problem 2

Explain the difference between the terms molecular mass and formula mass. To what type of compound does each term refer?

Daniel Kim
Daniel Kim
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04:21

Problem 3

Calculate the molecular mass (in amu) of each of the following substances: (a) $\mathrm{CH}_{3} \mathrm{Cl},$ (b) $\mathrm{N}_{2} \mathrm{O}_{4},$ (c) $\mathrm{SO}_{2},$ (d) $\mathrm{C}_{6} \mathrm{H}_{12},$ (e) $\mathrm{H}_{2} \mathrm{O}_{2}$
(f) $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11},(\mathrm{g}) \mathrm{NH}_{3}$.

Daniel Kim
Daniel Kim
Numerade Educator
04:31

Problem 4

Calculate the molecular mass (in amu) of each of the following substances: (a) $\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{O},(\mathrm{b}) \mathrm{H}_{2} \mathrm{SO}_{4},(\mathrm{c}) \mathrm{C}_{6} \mathrm{H}_{6},(\mathrm{d}) \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}$
(e) $\mathrm{BCl}_{3},$ (f) $\mathrm{N}_{2} \mathrm{O}_{5},(\mathrm{g}) \mathrm{H}_{3} \mathrm{PO}_{4}$.

Daniel Kim
Daniel Kim
Numerade Educator
02:38

Problem 5

Calculate the molecular mass or formula mass (in amu) of each of the following substances: (a) $\mathrm{CH}_{4},$ (b) $\mathrm{NO}_{2},$ (c) $\mathrm{SO}_{3},$ (d) $\mathrm{C}_{6} \mathrm{H}_{6}$
(e) $\mathrm{NaI},$ (f) $\mathrm{K}_{2} \mathrm{SO}_{4},(\mathrm{g}) \mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}$.

Dylan Miller
Dylan Miller
Numerade Educator
04:42

Problem 6

Calculate the molecular mass or formula mass (in amu) of each of the following substances: $(\mathrm{a}) \mathrm{Li}_{2} \mathrm{CO}_{3},(\mathrm{b}) \mathrm{C}_{2} \mathrm{H}_{6},(\mathrm{c}) \mathrm{NF}_{2}$
(d) $\mathrm{Al}_{2} \mathrm{O}_{3},(\mathrm{e}) \mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3},(\mathrm{f}) \mathrm{PCl}_{5},(\mathrm{g}) \mathrm{Mg}_{3} \mathrm{N}_{2}$.

Daniel Kim
Daniel Kim
Numerade Educator
02:20

Problem 7

Use ammonia ( $\mathrm{NH}_{3}$ ) to explain what is meant by the percent composition by mass of a compound.

Dylan Miller
Dylan Miller
Numerade Educator
03:33

Problem 8

Describe how the knowledge of the percent composition by mass of an unknown compound can help us identify the compound.

Benjamin Knudsen
Benjamin Knudsen
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02:12

Problem 9

Tin (Sn) exists in Earth's crust as $\mathrm{SnO}_{2}$. Calculate the percent composition by mass of $\mathrm{Sn}$ and $\mathrm{O}$ in $\mathrm{SnO}_{2}$.

Dylan Miller
Dylan Miller
Numerade Educator
02:03

Problem 10

For many years chloroform ( $\mathrm{CHCl}_{3}$ ) was used as an inhalation anesthetic in spite of the fact that it is also a toxic substance that may cause severe liver, kidney, and heart damage. Calculate the percent composition by mass of this compound.

Benjamin Knudsen
Benjamin Knudsen
Numerade Educator
06:25

Problem 11

All the substances listed here are fertilizers that contribute nitrogen to the soil. Which of these is the richest source of nitrogen on a mass percentage basis?
(a) Urea $\left[\left(\mathrm{NH}_{2}\right)_{2} \mathrm{CO}\right]$
(b) Ammonium nitrate $\left(\mathrm{NH}_{4} \mathrm{NO}_{3}\right)$
(c) Guanidine $\left[\mathrm{HNC}\left(\mathrm{NH}_{2}\right)_{2}\right]$
(d) Ammonia (NH $_{3}$ )

Daniel Kim
Daniel Kim
Numerade Educator
04:27

Problem 12

The anticaking agent added to Morton salt is calcium silicate $\left(\mathrm{CaSiO}_{3}\right) .$ This compound can absorb up to 2.5 times its mass of water and still remain a free-flowing powder. Calculate the percent composition of $\mathrm{CaSiO}_{3}$.

Pam Owens
Pam Owens
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05:04

Problem 13

Tooth enamel is $\mathrm{Ca}_{5}\left(\mathrm{PO}_{4}\right)_{3}(\mathrm{OH}) .$ Calculate the percent composition of the elements present.

Daniel Kim
Daniel Kim
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01:32

Problem 14

Use the formation of water from hydrogen and oxygen to explain the following terms: chemical reaction, reactant, and product.

Daniel Kim
Daniel Kim
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01:24

Problem 15

What is the difference between a chemical reaction and a chemical equation?

Daniel Kim
Daniel Kim
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01:07

Problem 16

Why must a chemical equation be balanced? What law is obeyed by a balanced chemical equation?

Daniel Kim
Daniel Kim
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00:36

Problem 17

Write the symbols used to represent gas, liquid, solid, and the aqueous phase in chemical equations.

Daniel Kim
Daniel Kim
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02:39

Problem 18

Write an unbalanced equation to represent each of the following reactions: (a) nitrogen and oxygen react to form nitrogen dioxide,
(b) dinitrogen pentoxide reacts to form dinitrogen tetroxide and oxygen, (c) ozone reacts to form oxygen, (d) chlorine and sodium iodide react to form iodine and sodium chloride, and (e) magnesium and oxygen react to form magnesium oxide.

Daniel Kim
Daniel Kim
Numerade Educator
04:21

Problem 19

Write an unbalanced equation to represent each of the following reactions: (a) potassium hydroxide and phosphoric acid react to form potassium phosphate and water; (b) zinc and silver chloride react to form zinc chloride and silver; (c) sodium hydrogen carbonate reacts to form sodium carbonate, water, and carbon dioxide; (d) ammonium nitrite reacts to form nitrogen and water; and (e) carbon dioxide and potassium hydroxide react to form potassium carbonate and water.

Daniel Kim
Daniel Kim
Numerade Educator
05:27

Problem 20

For each of the following unbalanced chemical equations, write the corresponding chemical statement.
(a) $\mathrm{S}_{8}+\mathrm{O}_{2} \longrightarrow \mathrm{SO}_{2}$
(b) $\mathrm{CH}_{4}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}$
(c) $\mathrm{N}_{2}+\mathrm{H}_{2} \longrightarrow \mathrm{NH}_{3}$
(d) $\mathrm{P}_{4} \mathrm{O}_{10}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{H}_{3} \mathrm{PO}_{4}$
(e) $\mathrm{S}+\mathrm{HNO}_{3} \longrightarrow \mathrm{H}_{2} \mathrm{SO}_{4}+\mathrm{NO}_{2}+\mathrm{H}_{2} \mathrm{O}$

Daniel Kim
Daniel Kim
Numerade Educator
06:56

Problem 21

For each of the following unbalanced chemical equations, write the corresponding chemical statement.
(a) $\mathrm{K}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{KOH}+\mathrm{H}_{2}$
(b) $\mathrm{Ba}(\mathrm{OH})_{2}+\mathrm{HCl} \longrightarrow \mathrm{BaCl}_{2}+\mathrm{H}_{2} \mathrm{O}$
(c) $\mathrm{Cu}+\mathrm{HNO}_{3} \longrightarrow \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{NO}+\mathrm{H}_{2} \mathrm{O}$
(d) $\mathrm{Al}+\mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}+\mathrm{H}_{2}$
(e) $\mathrm{HI} \longrightarrow \mathrm{H}_{2}+\mathrm{I}_{2}$

Daniel Kim
Daniel Kim
Numerade Educator
14:53

Problem 22

Balance the following equations using the method outlined in Section 3.3.
(a) $\mathrm{C}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}$
(b) $\mathrm{CO}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2}$
(c) $\mathrm{H}_{2}+\mathrm{Br}_{2} \longrightarrow \mathrm{HBr}$
(d) $\mathrm{K}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{KOH}+\mathrm{H}_{2}$
(e) $\mathrm{Mg}+\mathrm{O}_{2} \longrightarrow \mathrm{MgO}$
(f) $\mathrm{O}_{3} \longrightarrow \mathrm{O}_{2}$
$(g) \mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow \mathrm{H}_{2} \mathrm{O}+\mathrm{O}_{2}$
(h) $\mathrm{N}_{2}+\mathrm{H}_{2} \longrightarrow \mathrm{NH}_{3}$
(i) $\mathrm{Zn}+\mathrm{AgCl} \longrightarrow \mathrm{ZnCl}_{2}+\mathrm{Ag}$
(j) $\mathrm{S}_{8}+\mathrm{O}_{2} \longrightarrow \mathrm{SO}_{2}$
(k) $\mathrm{NaOH}+\mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}+\mathrm{H}_{2} \mathrm{O}$
(1) $\mathrm{Cl}_{2}+\mathrm{NaI} \longrightarrow \mathrm{NaCl}+\mathrm{I}_{2}$
$(\mathrm{m}) \mathrm{KOH}+\mathrm{H}_{3} \mathrm{PO}_{4} \longrightarrow \mathrm{K}_{3} \mathrm{PO}_{4}+\mathrm{H}_{2} \mathrm{O}$
(n) $\mathrm{CH}_{4}+\mathrm{Br}_{2} \longrightarrow \mathrm{CBr}_{4}+\mathrm{HBr}$

Daniel Kim
Daniel Kim
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Problem 23

Balance the following equations using the method outlined in Section 3.3.
(a) $\mathrm{N}_{2} \mathrm{O}_{5} \longrightarrow \mathrm{N}_{2} \mathrm{O}_{4}+\mathrm{O}_{2}$
(b) $\mathrm{KNO}_{3} \longrightarrow \mathrm{KNO}_{2}+\mathrm{O}_{2}$
(c) $\mathrm{NH}_{4} \mathrm{NO}_{3} \longrightarrow \mathrm{N}_{2} \mathrm{O}+\mathrm{H}_{2} \mathrm{O}$
(d) $\mathrm{NH}_{4} \mathrm{NO}_{2} \longrightarrow \mathrm{N}_{2}+\mathrm{H}_{2} \mathrm{O}$
(e) $\mathrm{NaHCO}_{3} \longrightarrow \mathrm{Na}_{2} \mathrm{CO}_{3}+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2}$
(f) $\mathrm{P}_{4} \mathrm{O}_{10}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{H}_{3} \mathrm{PO}_{4}$
(g) $\mathrm{HCl}+\mathrm{CaCO}_{3} \longrightarrow \mathrm{CaCl}_{2}+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2}$
(h) $\mathrm{Al}+\mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}+\mathrm{H}_{2}$
(i) $\mathrm{CO}_{2}+\mathrm{KOH} \longrightarrow \mathrm{K}_{2} \mathrm{CO}_{3}+\mathrm{H}_{2} \mathrm{O}$
(j) $\mathrm{CH}_{4}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}$
(k) $\mathrm{Be}_{2} \mathrm{C}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{Be}(\mathrm{OH})_{2}+\mathrm{CH}_{4}$
(l) $\mathrm{Cu}+\mathrm{HNO}_{3} \longrightarrow \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{NO}+\mathrm{H}_{2} \mathrm{O}$
$(\mathrm{m}) \mathrm{S}+\mathrm{HNO}_{3} \longrightarrow \mathrm{H}_{2} \mathrm{SO}_{4}+\mathrm{NO}_{2}+\mathrm{H}_{2} \mathrm{O}$
(n) $\mathrm{NH}_{3}+\mathrm{CuO} \longrightarrow \mathrm{Cu}+\mathrm{N}_{2}+\mathrm{H}_{2} \mathrm{O}$

Tom Comey
Tom Comey
Numerade Educator
01:18

Problem 24

Which of the following equations best represents the reaction shown in the diagram?
(a) $8 \mathrm{A}+4 \mathrm{B} \longrightarrow \mathrm{C}+\mathrm{D}$
(b) $4 \mathrm{A}+8 \mathrm{B} \longrightarrow 4 \mathrm{C}+4 \mathrm{D}$
(c) $2 \mathrm{A}+\mathrm{B} \longrightarrow \mathrm{C}+\mathrm{D}$
(d) $4 \mathrm{A}+2 \mathrm{B} \longrightarrow 4 \mathrm{C}+4 \mathrm{D}$
(e) $2 \mathrm{A}+4 \mathrm{B} \longrightarrow \mathrm{C}+\mathrm{D}$

Daniel Kim
Daniel Kim
Numerade Educator
01:07

Problem 25

Which of the following equations best represents the reaction shown in the diagram?
(a) $\mathrm{A}+\mathrm{B} \longrightarrow \mathrm{C}+\mathrm{D}$
(b) $6 \mathrm{A}+4 \mathrm{B} \longrightarrow \mathrm{C}+\mathrm{D}$
(c) $\mathrm{A}+2 \mathrm{B} \longrightarrow 2 \mathrm{C}+\mathrm{D}$
(d) $3 \mathrm{A}+2 \mathrm{B} \longrightarrow 2 \mathrm{C}+\mathrm{D}$
(e) $3 \mathrm{A}+2 \mathrm{B} \longrightarrow 4 \mathrm{C}+2 \mathrm{D}$

Daniel Kim
Daniel Kim
Numerade Educator
01:19

Problem 26

Define the term mole. What is the unit for mole in calculations? What does the mole have in common with the pair, the dozen, and the gross? What does Avogadro's number represent?

Dylan Miller
Dylan Miller
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01:11

Problem 27

What is the molar mass of an atom? What are the commonly used units for molar mass?

Benjamin Knudsen
Benjamin Knudsen
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01:03

Problem 28

What does the word empirical in empirical formula mean?

Daniel Kim
Daniel Kim
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02:50

Problem 29

If we know the empirical formula of a compound, what additional information do we need to determine its molecular formula?

Benjamin Knudsen
Benjamin Knudsen
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02:18

Problem 30

Earth's population is about 6.5 billion. Suppose that every person on Earth participates in a process of counting identical particles at the rate of two particles per second. How many years would it take to count $6.0 \times 10^{23}$ particles? Assume that there are 365 days in a year.

Daniel Kim
Daniel Kim
Numerade Educator
02:41

Problem 31

The thickness of a piece of paper is 0.0036 in. Suppose a certain book has an Avogadro's number of pages; calculate the thickness of the book in light-years. (Hint: See Problem 1.64 for the definition of light-year.)

Daniel Kim
Daniel Kim
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02:06

Problem 32

How many atoms are there in 5.10 moles of sulfur (S)?

Sharfa Farzandh
Sharfa Farzandh
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01:28

Problem 33

How many moles of cobalt (Co) atoms are there in $6.00 \times 10^{9}$ (6 billion) Co atoms?

Benjamin Knudsen
Benjamin Knudsen
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01:47

Problem 34

How many moles of calcium (Ca) atoms are in $77.4 \mathrm{g}$ of $\mathrm{Ca} ?$

Dr. Satish Ingale
Dr. Satish Ingale
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01:20

Problem 35

How many grams of gold (Au) are there in 15.3 moles of Au?

David Collins
David Collins
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02:49

Problem 36

What is the mass in grams of a single atom of each of the following elements: (a) Hg, (b) Ne?

Dr. Satish Ingale
Dr. Satish Ingale
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02:28

Problem 37

What is the mass in grams of a single atom of each of the following elements: (a) As, (b) Ni?

Benjamin Knudsen
Benjamin Knudsen
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01:52

Problem 38

What is the mass in grams of $1.00 \times 10^{12}$ lead (Pb) atoms?

Dylan Miller
Dylan Miller
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01:02

Problem 39

How many atoms are present in $3.14 \mathrm{g}$ of copper (Cu)?

Daniel Kim
Daniel Kim
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02:59

Problem 40

Which of the following has more atoms: $1.10 \mathrm{g}$ of hydrogen atoms or $14.7 \mathrm{g}$ of chromium atoms?

Dylan Miller
Dylan Miller
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01:39

Problem 41

Which of the following has a greater mass: two atoms of lead or $5.1 \times 10^{-23}$ mole of helium?

Daniel Kim
Daniel Kim
Numerade Educator
01:51

Problem 42

Calculate the molar mass of the following substances: (a) $\mathrm{Li}_{2} \mathrm{CO}_{3}$
(b) $\mathrm{CS}_{2},$ (c) $\mathrm{CHCl}_{3}$ (chloroform), (d) $\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{6}$ (ascorbic acid, or vitamin $\mathrm{C}$ ), (e) $\mathrm{KNO}_{3}$, (f) $\mathrm{Mg}_{3} \mathrm{N}_{2}$.

Benjamin Knudsen
Benjamin Knudsen
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01:23

Problem 43

Calculate the molar mass of a compound if 0.372 mole of it has a mass of $152 \mathrm{g}$.

Dylan Miller
Dylan Miller
Numerade Educator
01:16

Problem 44

How many molecules of ethane $\left(\mathrm{C}_{2} \mathrm{H}_{6}\right)$ are present in $0.334 \mathrm{g}$ of $\mathrm{C}_{2} \mathrm{H}_{6} ?$

Nishant Kumar
Nishant Kumar
Numerade Educator
02:49

Problem 45

Calculate the number of $\mathrm{C}, \mathrm{H},$ and $\mathrm{O}$ atoms in $1.50 \mathrm{g}$ of glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right),$ a sugar.

Dylan Miller
Dylan Miller
Numerade Educator
03:32

Problem 46

Urea $\left[\left(\mathrm{NH}_{2}\right)_{2} \mathrm{CO}\right]$ is used for fertilizer and many other things. Calculate the number of $\mathrm{N}, \mathrm{C}, \mathrm{O},$ and $\mathrm{H}$ atoms in $1.68 \times 10^{4} \mathrm{g}$ of urea.

Daniel Kim
Daniel Kim
Numerade Educator
02:22

Problem 47

Pheromones are a special type of compound secreted by the females of many insect species to attract the males for mating. One pheromone has the molecular formula $\mathrm{C}_{19} \mathrm{H}_{38} \mathrm{O}$. Normally, the amount of this pheromone secreted by a female insect is about $1.0 \times 10^{-12} \mathrm{g} .$ How many molecules are there in this quantity?

Dylan Miller
Dylan Miller
Numerade Educator
02:44

Problem 48

The density of water is $1.00 \mathrm{g} / \mathrm{mL}$ at $4^{\circ} \mathrm{C}$. How many water molecules are present in $2.56 \mathrm{mL}$ of water at this temperature?

Benjamin Knudsen
Benjamin Knudsen
Numerade Educator
03:37

Problem 49

Cinnamic alcohol is used mainly in perfumery, particularly in soaps and cosmetics. Its molecular formula is $\mathrm{C}_{9} \mathrm{H}_{10} \mathrm{O}$. (a) Calculate the percent composition by mass of $\mathrm{C}, \mathrm{H},$ and $\mathrm{O}$ in cinnamic alcohol. (b) How many molecules of cinnamic alcohol are contained in a sample of mass $0.469 \mathrm{g} ?$

Dylan Miller
Dylan Miller
Numerade Educator
02:33

Problem 50

Allicin is the compound responsible for the characteristic smell of garlic. An analysis of the compound gives the following percent composition by mass: $\mathrm{C}: 44.4$ percent; $\mathrm{H}: 6.21$ percent; $\mathrm{S}: 39.5$ percent; O: 9.86 percent. Calculate its empirical formula. What is its molecular formula given that its molar mass is about $162 \mathrm{g} ?$

Dylan Miller
Dylan Miller
Numerade Educator
05:06

Problem 51

Peroxyacylnitrate (PAN) is one of the components of smog. It is a compound of $\mathrm{C}, \mathrm{H}, \mathrm{N},$ and $\mathrm{O} .$ Determine the percent composition of oxygen and the empirical formula from the following percent composition by mass: 19.8 percent $\mathrm{C}, 2.50$ percent $\mathrm{H}, 11.6$ percent N. What is its molecular formula given that its molar mass is about 120 g?

Daniel Kim
Daniel Kim
Numerade Educator
01:38

Problem 52

The formula for rust can be represented by $\mathrm{Fe}_{2} \mathrm{O}_{3}$. How many moles of Fe are present in $24.6 \mathrm{g}$ of the compound?

Dylan Miller
Dylan Miller
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01:30

Problem 53

How many grams of sulfur (S) are needed to react completely with $246 \mathrm{g}$ of mercury (Hg) to form HgS?

Daniel Kim
Daniel Kim
Numerade Educator
01:51

Problem 54

Calculate the mass in grams of iodine $\left(\mathrm{I}_{2}\right)$ that will react completely with $20.4 \mathrm{g}$ of aluminum (Al) to form aluminum iodide $\left(\mathrm{AlI}_{3}\right)$

Daniel Kim
Daniel Kim
Numerade Educator
01:42

Problem 55

Tin(II) fluoride $\left(\mathrm{SnF}_{2}\right)$ is often added to toothpaste as an ingredient to prevent tooth decay. What is the mass of $\mathrm{F}$ in grams in $24.6 \mathrm{g}$ of the compound?

Daniel Kim
Daniel Kim
Numerade Educator
05:04

Problem 56

Determine the empirical formulas of the compounds with the following compositions: (a) 2.1 percent H, 65.3 percent O, 32.6 percent $S,$ (b) 20.2 percent $A 1,79.8$ percent $C$ l.

Daniel Kim
Daniel Kim
Numerade Educator
04:54

Problem 57

Determine the empirical formulas of the compounds with the following compositions: (a) 40.1 percent C, 6.6 percent H, 53.3 percent $\mathrm{O},(\mathrm{b}) 18.4$ percent $\mathrm{C}, 21.5$ percent $\mathrm{N}, 60.1$ percent $\mathrm{K}$.

Daniel Kim
Daniel Kim
Numerade Educator
01:40

Problem 58

The empirical formula of a compound is CH. If the molar mass of this compound is about $78 \mathrm{g},$ what is its molecular formula?

Daniel Kim
Daniel Kim
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02:11

Problem 59

The molar mass of caffeine is $194.19 \mathrm{g}$. Is the molecular formula of caffeine $\mathrm{C}_{4} \mathrm{H}_{5} \mathrm{N}_{2} \mathrm{O}$ or $\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{N}_{4} \mathrm{O}_{2} ?$

Dylan Miller
Dylan Miller
Numerade Educator
07:39

Problem 60

Monosodium glutamate (MSG), a food-flavor enhancer, has been blamed for "Chinese restaurant syndrome," the symptoms of which are headaches and chest pains. MSG has the following composition by mass: 35.51 percent $\mathrm{C}, 4.77$ percent $\mathrm{H}, 37.85$ percent $\mathrm{O}, 8.29$ percent $\mathrm{N},$ and 13.60 percent $\mathrm{Na}$. What is its molecular formula if its molar mass is about $169 \mathrm{g} ?$

Daniel Kim
Daniel Kim
Numerade Educator
04:14

Problem 61

Toxicologists use the term $L D_{50}$ to describe the number of grams of a substance per kilogram of body weight that is a lethal dose for 50 percent of test animals. Calculate the number of arsenic(VI) oxide molecules corresponding to an $L D_{50}$ value of 0.015 for a $184-1 \mathrm{b}$ man, assuming that the test animals and humans have the same LD $_{50}$.

Adedamola Opalade
Adedamola Opalade
Numerade Educator
04:55

Problem 62

Chemical analysis shows that the oxygen-carrying protein hemoglobin is 0.34 percent Fe by mass. What is the minimum possible molar mass of hemoglobin? The actual molar mass of hemoglobin is about 65,000 g. How would you account for the discrepancy between your minimum value and the experimental value?

Pam Owens
Pam Owens
Numerade Educator
01:12

Problem 63

Explain how the combined mass of $\mathrm{CO}_{2}$ and $\mathrm{H}_{2} \mathrm{O}$ produced in combustion analysis can be greater than the mass of the sample that is combusted.

Daniel Kim
Daniel Kim
Numerade Educator
01:06

Problem 64

Explain why, in combustion analysis, we cannot determine the amount of oxygen in the sample directly from the amount of oxygen in the products $\mathrm{H}_{2} \mathrm{O}$ and $\mathrm{CO}_{2}$.

Daniel Kim
Daniel Kim
Numerade Educator
07:31

Problem 65

Menthol is a flavoring agent extracted from peppermint oil. It contains $\mathrm{C}, \mathrm{H},$ and $\mathrm{O}$. In one combustion analysis, $10.00 \mathrm{mg}$ of the substance yields $11.53 \mathrm{mg} \mathrm{H}_{2} \mathrm{O}$ and $28.16 \mathrm{mg} \mathrm{CO}_{2} .$ What is the empirical formula of menthol?

Nadia Lara
Nadia Lara
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Problem 66

Determine the empirical formula of an organic compound containing only $\mathrm{C}$ and $\mathrm{H}$ given that combustion of a $1.50-\mathrm{g}$ sample of the compound produces $4.71 \mathrm{g} \mathrm{CO}_{2}$ and $1.93 \mathrm{g} \mathrm{H}_{2} \mathrm{O}$.

Bridger Johnston
Bridger Johnston
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Problem 67

Lactic acid, which consists of $\mathrm{C}, \mathrm{H},$ and $\mathrm{O},$ has long been thought to be responsible for muscle soreness following strenuous exercise. Determine the empirical formula of lactic acid given that combustion of a 10.0 -g sample produces $14.7 \mathrm{g} \mathrm{CO}_{2}$ and $6.00 \mathrm{g} \mathrm{H}_{2} \mathrm{O}$.

Bridger Johnston
Bridger Johnston
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Problem 68

Perchloroethylene, also known as "perc," is the solvent used in most dry cleaning. It consists of $C$ and Cl. Determine the empirical formula of perchloroethylene given that a $2.58-\mathrm{g}$ sample yields $1.37 \mathrm{g} \mathrm{CO}_{2}$ in a combustion analysis experiment.

Bridger Johnston
Bridger Johnston
Numerade Educator
03:34

Problem 69

Paradichlorobenzene, a common ingredient in solid air fresheners, contains only $\mathrm{C}, \mathrm{H},$ and $\mathrm{Cl}$ and has a molar mass of about $147 \mathrm{g}$. Given that combustion of $1.68 \mathrm{g}$ of this compound produces $3.02 \mathrm{g} \mathrm{CO}_{2}$ and $0.412 \mathrm{g} \mathrm{H}_{2} \mathrm{O}$, determine its empirical and molecular formulas.

Susan Hallstrom
Susan Hallstrom
Numerade Educator
05:53

Problem 70

Ascorbic acid (vitamin C) contains C, H, and O. In one combustion analysis, $5.24 \mathrm{g}$ of ascorbic acid yields $7.86 \mathrm{g} \mathrm{CO}_{2}$ and $2.14 \mathrm{g} \mathrm{H}_{2} \mathrm{O}$. Calculate the empirical formula and molecular formula of ascorbic acid given that its molar mass is about $176 \mathrm{g}$.

David Collins
David Collins
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Problem 71

The amino acid cysteine plays an important role in the threedimensional structure of proteins by forming "disulfide bridges." The percent composition of cysteine is 29.74 percent $C$, 5.82 percent $\mathrm{H}, 26.41$ percent $\mathrm{O}, 11.56$ percent $\mathrm{N},$ and 26.47 percent S. What is the molecular formula if its molar mass is approximately $121 \mathrm{g} ?$

Susan Hallstrom
Susan Hallstrom
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01:09

Problem 72

On what law is stoichiometry based? Why is it essential to use balanced equations in solving stoichiometric problems?

Daniel Kim
Daniel Kim
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02:01

Problem 73

Describe the steps involved in balancing a chemical equation.

Daniel Kim
Daniel Kim
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01:13

Problem 74

Consider the combustion of carbon monoxide (CO) in oxygen gas:
$$2 \mathrm{CO}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CO}_{2}(g)$$
Starting with 3.60 moles of $\mathrm{CO}$, calculate the number of moles of $\mathrm{CO}_{2}$ produced if there is enough oxygen gas to react with all the CO.

Daniel Kim
Daniel Kim
Numerade Educator
01:22

Problem 75

Silicon tetrachloride ( $\mathrm{SiCl}_{4}$ ) can be prepared by heating Si in chlorine gas:
$$\mathrm{Si}(s)+2 \mathrm{Cl}_{2}(g) \longrightarrow \mathrm{SiCl}_{4}(l)$$
In one reaction, 0.507 mole of $\mathrm{SiCl}_{4}$ is produced. How many moles of molecular chlorine were used in the reaction?

Daniel Kim
Daniel Kim
Numerade Educator
01:52

Problem 76

Ammonia is a principal nitrogen fertilizer. It is prepared by the reaction between hydrogen and nitrogen:
$$3 \mathrm{H}_{2}(g)+\mathrm{N}_{2}(g) \longrightarrow 2 \mathrm{NH}_{3}(g)$$
In a particular reaction, 6.0 moles of $\mathrm{NH}_{3}$ were produced. How many moles of $\mathrm{H}_{2}$ and how many moles of $\mathrm{N}_{2}$ were consumed to produce this amount of $\mathrm{NH}_{3} ?$

Daniel Kim
Daniel Kim
Numerade Educator
01:30

Problem 77

Consider the combustion of butane $\left(\mathrm{C}_{4} \mathrm{H}_{10}\right):$
$$2 \mathrm{C}_{4} \mathrm{H}_{10}(g)+13 \mathrm{O}_{2}(g) \longrightarrow 8 \mathrm{CO}_{2}(g)+10 \mathrm{H}_{2} \mathrm{O}(l)$$
In a particular reaction, 5.0 moles of $\mathrm{C}_{4} \mathrm{H}_{10}$ react with an excess of $\mathrm{O}_{2} .$ Calculate the number of moles of $\mathrm{CO}_{2}$ formed.

Daniel Kim
Daniel Kim
Numerade Educator
02:33

Problem 78

The annual production of sulfur dioxide from burning coal and fossil fuels, auto exhaust, and other sources is about 26 million tons. The equation for the reaction is
$$\mathrm{S}(s)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{SO}_{2}(g)$$
How much sulfur (in tons), present in the original materials, would result in that quantity of $\mathrm{SO}_{2} ?$

Daniel Kim
Daniel Kim
Numerade Educator
View

Problem 79

When baking soda (sodium bicarbonate or sodium hydrogen carbonate, $\mathrm{NaHCO}_{3}$ ) is heated, it releases carbon dioxide gas, which is responsible for the rising of cookies, doughnuts, and bread. (a) Write a balanced equation for the decomposition of the compound (one of the products is $\mathrm{Na}_{2} \mathrm{CO}_{3}$ ). (b) Calculate the mass of $\mathrm{NaHCO}_{3}$ required to produce $20.5 \mathrm{g}$ of $\mathrm{CO}_{2}$.

Bridger Johnston
Bridger Johnston
Numerade Educator
02:59

Problem 80

When potassium cyanide (KCN) reacts with acids, a deadly poisonous gas, hydrogen cyanide (HCN), is given off. Here is the equation:
$$\mathrm{KCN}(a q)+\mathrm{HCl}(a q) \longrightarrow \mathrm{KCl}(a q)+\mathrm{HCN}(g)$$
If a sample of $0.140 \mathrm{g}$ of $\mathrm{KCN}$ is treated with an excess of $\mathrm{HCl}$, calculate the amount of HCN formed, in grams.

Daniel Kim
Daniel Kim
Numerade Educator
03:43

Problem 81

Fermentation is a complex chemical process of wine making in which glucose is converted into ethanol and carbon dioxide:
$$\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} \longrightarrow 2 \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}+2 \mathrm{CO}_{2}$$
Starting with $500.4 \mathrm{g}$ of glucose, what is the maximum amount of ethanol in grams and in liters that can be obtained by this process (density of ethanol $=0.789 \mathrm{g} / \mathrm{mL}$ )?

Daniel Kim
Daniel Kim
Numerade Educator
01:26

Problem 82

Each copper(II) sulfate unit is associated with five water molecules in crystalline copper(II) sulfate pentahydrate (CuSO $_{4}$ $\left.\cdot 5 \mathrm{H}_{2} \mathrm{O}\right) \cdot$ When this compound is heated in air above $100^{\circ} \mathrm{C},$ it loses the water molecules and also its blue color:
$$\mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{CuSO}_{4}+5 \mathrm{H}_{2} \mathrm{O}$$
If $9.60 \mathrm{g}$ of $\mathrm{CuSO}_{4}$ are left after heating $15.01 \mathrm{g}$ of the blue compound, calculate the number of moles of $\mathrm{H}_{2} \mathrm{O}$ originally present in the compound.

Daniel Kim
Daniel Kim
Numerade Educator
01:31

Problem 83

For many years the extraction of gold $-$ that is, the separation of gold from other materials- involved the use of potassium cyanide:
$$4 \mathrm{Au}+8 \mathrm{KCN}+\mathrm{O}_{2}+2 \mathrm{H}_{2} \mathrm{O} \longrightarrow 4 \mathrm{KAu}(\mathrm{CN})_{2}+4 \mathrm{KOH}$$
What is the minimum amount of $\mathrm{KCN}$ in moles needed to extract 29.0 g (about an ounce) of gold?

Daniel Kim
Daniel Kim
Numerade Educator
03:02

Problem 84

Limestone (CaCO $_{3}$ ) is decomposed by heating to quicklime (CaO) and carbon dioxide. Calculate how many grams of quicklime can be produced from $1.0 \mathrm{kg}$ of limestone.

Daniel Kim
Daniel Kim
Numerade Educator
03:08

Problem 85

Nitrous oxide $\left(\mathrm{N}_{2} \mathrm{O}\right)$ is also called "laughing gas." It can be prepared by the thermal decomposition of ammonium nitrate $\left(\mathrm{NH}_{4} \mathrm{NO}_{3}\right) .$ The other product is $\mathrm{H}_{2} \mathrm{O}$. (a) Write a balanced equation for this reaction. (b) How many grams of $\mathrm{N}_{2} \mathrm{O}$ are formed if 0.46 mole of $\mathrm{NH}_{4} \mathrm{NO}_{3}$ is used in the reaction?

Daniel Kim
Daniel Kim
Numerade Educator
03:23

Problem 86

The fertilizer ammonium sulfate $\left[\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}\right]$ is prepared by the reaction between ammonia $\left(\mathrm{NH}_{3}\right)$ and sulfuric acid:
$$2 \mathrm{NH}_{3}(g)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}(a q)$$
How many kilograms of $\mathrm{NH}_{3}$ are needed to produce $1.00 \times 10^{5}$ $\mathrm{kg}$ of $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} ?$

Daniel Kim
Daniel Kim
Numerade Educator
03:23

Problem 87

A common laboratory preparation of oxygen gas is the thermal decomposition of potassium chlorate (KClO $_{3}$ ). Assuming complete decomposition, calculate the number of grams of $\mathrm{O}_{2}$ gas that can be obtained from $46.0 \mathrm{g}$ of $\mathrm{KClO}_{3}$. (The products are $\left.\mathrm{KCl} \text { and } \mathrm{O}_{2} .\right)$

Daniel Kim
Daniel Kim
Numerade Educator
02:12

Problem 88

Define limiting reactant and excess reactant. What is the significance of the limiting reactant in predicting the amount of the product obtained in a reaction? Can there be a limiting reactant if only one reactant is present?

Daniel Kim
Daniel Kim
Numerade Educator
01:20

Problem 89

Give an everyday example that illustrates the limiting reactant concept.

Daniel Kim
Daniel Kim
Numerade Educator
00:47

Problem 90

Why is the theoretical yield of a reaction determined only by the amount of the limiting reactant?

Daniel Kim
Daniel Kim
Numerade Educator
01:17

Problem 91

Why is the actual yield of a reaction almost always smaller than the theoretical yield?

Daniel Kim
Daniel Kim
Numerade Educator
View

Problem 92

Consider the reaction
$$2 \mathrm{A}+\mathrm{B} \longrightarrow \mathrm{C}$$
(a) In the diagram here that represents the reaction, which reactant, A or B, is the limiting reactant? (b) Assuming a complete reaction, draw a molecular-model representation of the amounts of reactants and products left after the reaction. The atomic arrangement in $\mathrm{C}$ is ABA.

Susan Hallstrom
Susan Hallstrom
Numerade Educator
02:31

Problem 93

Consider the reaction
$$\mathrm{N}_{2}+3 \mathrm{H}_{2} \longrightarrow 2 \mathrm{NH}_{3}$$
Assuming each model represents one mole of the substance, show the number of moles of the product and the excess reactant left after the complete reaction.

Nicole Krahulik
Nicole Krahulik
Numerade Educator
02:28

Problem 94

Nitric oxide (NO) reacts with oxygen gas to form nitrogen dioxide (NO $_{2}$ ), a dark-brown gas:
$$2 \mathrm{NO}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{NO}_{2}(g)$$ In one experiment 0.886 mole of $\mathrm{NO}$ is mixed with 0.503 mole of $\mathrm{O}_{2} .$ Determine which of the two reactants is the limiting reactant. Calculate also the number of moles of $\mathrm{NO}_{2}$ produced.

Daniel Kim
Daniel Kim
Numerade Educator
05:39

Problem 95

The depletion of ozone $\left(\mathrm{O}_{3}\right)$ in the stratosphere has been a matter of great concern among scientists in recent years. It is believed that ozone can react with nitric oxide (NO) that is discharged from high-altitude jet planes. The reaction is
$$\mathrm{O}_{3}+\mathrm{NO} \longrightarrow \mathrm{O}_{2}+\mathrm{NO}_{2}$$
If $0.740 \mathrm{g}$ of $\mathrm{O}_{3}$ reacts with $0.670 \mathrm{g}$ of $\mathrm{NO}$, how many grams of $\mathrm{NO}_{2}$ will be produced? Which compound is the limiting reactant? Calculate the number of moles of the excess reactant remaining at the end of the reaction.

Daniel Kim
Daniel Kim
Numerade Educator
03:09

Problem 96

Propane $\left(\mathrm{C}_{3} \mathrm{H}_{8}\right)$ is a minor component of natural gas and is used in domestic cooking and heating. (a) Balance the following equation representing the combustion of propane in air:
$$\mathrm{C}_{3} \mathrm{H}_{8}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}$$
(b) How many grams of carbon dioxide can be produced by burning 3.65 moles of propane? Assume that oxygen is the excess reactant in this reaction.

Daniel Kim
Daniel Kim
Numerade Educator
04:36

Problem 97

Consider the reaction
$$\mathrm{MnO}_{2}+4 \mathrm{HCl} \longrightarrow \mathrm{MnCl}_{2}+\mathrm{Cl}_{2}+2 \mathrm{H}_{2} \mathrm{O}$$
If 0.86 mole of $\mathrm{MnO}_{2}$ and $48.2 \mathrm{g}$ of $\mathrm{HCl}$ react, which reactant will be used up first? How many grams of $\mathrm{Cl}_{2}$ will be produced?

Daniel Kim
Daniel Kim
Numerade Educator
View

Problem 98

Hydrogen fluoride is used in the manufacture of Freons (which destroy ozone in the stratosphere) and in the production of aluminum metal. It is prepared by the reaction
$$\mathrm{CaF}_{2}+\mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow \mathrm{CaSO}_{4}+2 \mathrm{HF}$$
In one process $6.00 \mathrm{kg}$ of $\mathrm{CaF}_{2}$ is treated with an excess of $\mathrm{H}_{2} \mathrm{SO}_{4}$ and yields $2.86 \mathrm{kg}$ of $\mathrm{HF}$. Calculate the percent yield of $\mathrm{HF}$.

Bridger Johnston
Bridger Johnston
Numerade Educator
03:55

Problem 99

Nitroglycerin $\left(\mathrm{C}_{3} \mathrm{H}_{5} \mathrm{N}_{3} \mathrm{O}_{9}\right)$ is a powerful explosive. Its decomposition may be represented by
$$4 \mathrm{C}_{3} \mathrm{H}_{5} \mathrm{N}_{3} \mathrm{O}_{9} \longrightarrow 6 \mathrm{N}_{2}+12 \mathrm{CO}_{2}+10 \mathrm{H}_{2} \mathrm{O}+\mathrm{O}_{2}$$
This reaction generates a large amount of heat and gaseous products. It is the sudden formation of these gases, together with their rapid expansion, that produces the explosion. (a) What is the maximum amount of $\mathrm{O}_{2}$ in grams that can be obtained from 2.00
$\times 10^{2} \mathrm{g}$ of nitroglycerin? (b) Calculate the percent yield in this reaction if the amount of $\mathrm{O}_{2}$ generated is found to be $6.55 \mathrm{g}$.

Daniel Kim
Daniel Kim
Numerade Educator
04:50

Problem 100

Titanium(IV) oxide (TiO_) is a white substance produced by the action of sulfuric acid on the mineral ilmenite (FeTiO $_{3}$ ):
$$\mathrm{FeTiO}_{3}+\mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow \mathrm{TiO}_{2}+\mathrm{FeSO}_{4}+\mathrm{H}_{2} \mathrm{O}$$
Its opaque and nontoxic properties make it suitable as a pigment in plastics and paints. In one process $8.00 \times 10^{3} \mathrm{kg}$ of $\mathrm{FeTiO}_{3}$ yielded $3.67 \times 10^{3} \mathrm{kg}$ of $\mathrm{TiO}_{2} .$ What is the percent yield of the reaction?

Daniel Kim
Daniel Kim
Numerade Educator
04:44

Problem 101

Ethylene $\left(\mathrm{C}_{2} \mathrm{H}_{4}\right),$ an important industrial organic chemical, can be prepared by heating hexane $\left(\mathrm{C}_{6} \mathrm{H}_{14}\right)$ at $800^{\circ} \mathrm{C}$ :
$$\mathrm{C}_{6} \mathrm{H}_{14} \longrightarrow \mathrm{C}_{2} \mathrm{H}_{4}+\text { other products }$$
If the yield of ethylene production is 42.5 percent, what mass of hexane must be used to produce 481 g of ethylene?

Daniel Kim
Daniel Kim
Numerade Educator
05:50

Problem 102

When heated, lithium reacts with nitrogen to form lithium nitride:
$$6 \mathrm{Li}(s)+\mathrm{N}_{2}(g) \longrightarrow 2 \mathrm{Li}_{3} \mathrm{N}(s)$$
What is the theoretical yield of $L$ is $N$ in grams when 12.3 g of $L$ i are heated with $33.6 \mathrm{g}$ of $\mathrm{N}_{2}$ ? If the actual yield of $\mathrm{Li}_{3} \mathrm{N}$ is $5.89 \mathrm{g}$, what is the percent yield of the reaction?

Daniel Kim
Daniel Kim
Numerade Educator
06:18

Problem 103

Disulfide dichloride $\left(\mathrm{S}_{2} \mathrm{Cl}_{2}\right)$ is used in the vulcanization of rubber, a process that prevents the slippage of rubber molecules past one another when stretched. It is prepared by heating sulfur in an atmosphere of chlorine:
$$\mathrm{S}_{8}(l)+4 \mathrm{Cl}_{2}(g) \longrightarrow 4 \mathrm{S}_{2} \mathrm{Cl}_{2}(l)$$
What is the theoretical yield of $S_{2} \mathrm{Cl}_{2}$ in grams when $4.06 \mathrm{g}$ of
$S_{8}$ are heated with $6.24 \mathrm{g}$ of $\mathrm{Cl}_{2} ?$ If the actual yield of $\mathrm{S}_{2} \mathrm{Cl}_{2}$ is $6.55 \mathrm{g},$ what is the percent yield?

Daniel Kim
Daniel Kim
Numerade Educator
02:07

Problem 104

Determine whether each of the following equations represents a combination reaction, a decomposition reaction, or a combustion reaction: (a) $2 \mathrm{NaHCO}_{3} \longrightarrow \mathrm{Na}_{2} \mathrm{CO}_{3}+\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O},$ (b) $\mathrm{NH}_{3}$
$+\mathrm{HCl} \longrightarrow \mathrm{NH}_{4} \mathrm{Cl},(\mathrm{c}) 2 \mathrm{CH}_{3} \mathrm{OH}+3 \mathrm{O}_{2} \longrightarrow 2 \mathrm{CO}_{2}+$
$4 \mathrm{H}_{2} \mathrm{O}$.

Daniel Kim
Daniel Kim
Numerade Educator
02:17

Problem 105

Determine whether each of the following equations represents a combination reaction, a decomposition reaction, or a combustion reaction: (a) $\mathrm{C}_{3} \mathrm{H}_{8}+5 \mathrm{O}_{2} \longrightarrow 3 \mathrm{CO}_{2}+4 \mathrm{H}_{2} \mathrm{O},$ (b) $2 \mathrm{NF}_{2} \longrightarrow$
$\mathrm{N}_{2} \mathrm{F}_{4},(\mathrm{c}) \mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{CuSO}_{4}+5 \mathrm{H}_{2} \mathrm{O}$.

Daniel Kim
Daniel Kim
Numerade Educator
03:20

Problem 106

The diagram represents the products $\left(\mathrm{CO}_{2} \text { and } \mathrm{H}_{2} \mathrm{O}\right) \mathrm{f}$ formed after \right. the combustion of a hydrocarbon (a compound containing only C and H atoms). Write an equation for the reaction. (Hint: The molar mass of the hydrocarbon is about $30 \mathrm{g}$.)

Daniel Kim
Daniel Kim
Numerade Educator
02:30

Problem 107

Consider the reaction of hydrogen gas with oxygen gas:
$$2 \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(g)$$ Assuming a complete reaction, which of the diagrams (a-d) shown here represents the amounts of reactants and products left after the reaction?

Daniel Kim
Daniel Kim
Numerade Educator
View

Problem 108

Cysteine, shown here, is one of the 20 amino acids found in proteins in humans. Write the molecular formula of cysteine, and calculate its molar mass.

Bridger Johnston
Bridger Johnston
Numerade Educator
01:32

Problem 109

Isoflurane, shown here, is a common inhalation anesthetic. Write its molecular formula, and calculate its molar mass.

Daniel Kim
Daniel Kim
Numerade Educator
09:15

Problem 110

Industrially, nitric acid is produced by the Ostwald process represented by the following equations:
$$\begin{array}{c}
4 \mathrm{NH}_{3}(g)+5 \mathrm{O}_{2}(g) \longrightarrow 4 \mathrm{NO}(g)+6 \mathrm{H}_{2} \mathrm{O}(l) \\
2 \mathrm{NO}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{NO}_{2}(g) \\
2 \mathrm{NO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{HNO}_{3}(a q)+\mathrm{HNO}_{2}(a q)
\end{array}$$
What mass of $\mathrm{NH}_{3}$ (in grams) must be used to produce 1.00 ton of $\mathrm{HNO}_{3}$ by the Ostwald process, assuming an 80 percent yield in each step (1 ton $=2000$ lb; 1 b $=453.6$ g)?

Daniel Kim
Daniel Kim
Numerade Educator
04:39

Problem 111

A sample of a compound of $\mathrm{Cl}$ and $\mathrm{O}$ reacts with an excess of
$\mathrm{H}_{2}$ to give $0.233 \mathrm{g}$ of $\mathrm{HCl}$ and $0.403 \mathrm{g}$ of $\mathrm{H}_{2} \mathrm{O}$. Determine the empirical formula of the compound.

Daniel Kim
Daniel Kim
Numerade Educator
02:33

Problem 112

The atomic mass of element $X$ is 33.42 amu. A 27.22 -g sample of $\mathrm{X}$ combines with $84.10 \mathrm{g}$ of another element $\mathrm{Y}$ to form a compound XY. Calculate the atomic mass of Y.

Daniel Kim
Daniel Kim
Numerade Educator
01:17

Problem 113

How many moles of $\mathrm{O}$ are needed to combine with 0.212 mole of
C to form (a) $\mathrm{CO}$ and (b) $\mathrm{CO}_{2}$ ?

Daniel Kim
Daniel Kim
Numerade Educator
06:07

Problem 114

The aluminum sulfate hydrate $\left[\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3} \cdot x \mathrm{H}_{2} \mathrm{O}\right]$ contains 8.10 percent Al by mass. Calculate $x$, that is, the number of water molecules associated with each $\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}$ unit.

Daniel Kim
Daniel Kim
Numerade Educator
08:29

Problem 115

The explosive nitroglycerin $\left(\mathrm{C}_{3} \mathrm{H}_{5} \mathrm{N}_{3} \mathrm{O}_{9}\right)$ has also been used as a drug to treat heart patients to relieve pain (angina pectoris). We now know that nitroglycerin produces nitric oxide (NO), which causes muscles to relax and allows the arteries to dilate. If each nitroglycerin molecule releases one NO per atom of $\mathrm{N}$, calculate the mass percent of NO in nitroglycerin.

Shazia Naz
Shazia Naz
Numerade Educator
04:42

Problem 116

The compound 2,3-dimercaptopropanol (HSCH_CHSHCH_OH), commonly known as British Anti-Lewisite (BAL), was developed during World War I as an antidote to arsenic-containing poison gas. (a) If each BAL molecule binds one arsenic (As) atom, how many As atoms can be removed by $1.0 \mathrm{g}$ of $\mathrm{BAL}$ ? (b) $\mathrm{BAL}$ can also be used to remove poisonous heavy metals like mercury (Hg) and lead (Pb). If each BAL binds one Hg atom, calculate the mass percent of $\mathrm{Hg}$ in a BAL-Hg complex. (An $\mathrm{H}$ atom is removed when a BAL molecule binds an Hg atom.)

Daniel Kim
Daniel Kim
Numerade Educator
03:11

Problem 117

Mustard gas $\left(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{Cl}_{2} \mathrm{S}\right)$ is a poisonous gas that was used in World War I and banned afterward. It causes general destruction of body tissues, resulting in the formation of large water blisters. There is no effective antidote. Calculate the percent composition by mass of the elements in mustard gas.

Daniel Kim
Daniel Kim
Numerade Educator
01:14

Problem 118

The carat is the unit of mass used by jewelers. One carat is exactly $200 \mathrm{mg} .$ How many carbon atoms are present in a 2 -carat diamond?

Daniel Kim
Daniel Kim
Numerade Educator
03:03

Problem 119

An iron bar weighed 664 g. After the bar had been standing in moist air for a month, exactly one-eighth of the iron turned to rust $\left(\mathrm{Fe}_{2} \mathrm{O}_{3}\right) .$ Calculate the final mass of the iron bar and rust.

Daniel Kim
Daniel Kim
Numerade Educator
02:37

Problem 120

A certain metal oxide has the formula MO where M denotes the metal. A 39.46-g sample of the compound is strongly heated in an atmosphere of hydrogen to remove oxygen as water molecules. At the end, $31.70 \mathrm{g}$ of the metal is left over. If $\mathrm{O}$ has an atomic mass of 16.00 amu, calculate the atomic mass of $M$ and identify the element.

Daniel Kim
Daniel Kim
Numerade Educator
04:41

Problem 121

An impure sample of zinc (Zn) is treated with an excess of sulfuric acid $\left(\mathrm{H}_{2} \mathrm{SO}_{4}\right)$ to form zinc sulfate $\left(\mathrm{ZnSO}_{4}\right)$ and molecular hydrogen $\left(\mathrm{H}_{2}\right)$. (a) Write a balanced equation for the reaction.
(b) If $0.0764 \mathrm{g}$ of $\mathrm{H}_{2}$ is obtained from $3.86 \mathrm{g}$ of the sample, calculate the percent purity of the sample. (c) What assumptions must you make in part (b)?

Daniel Kim
Daniel Kim
Numerade Educator
03:21

Problem 122

One of the reactions that occurs in a blast furnace, where iron ore is converted to cast iron, is
$$\mathrm{Fe}_{2} \mathrm{O}_{3}+3 \mathrm{CO} \longrightarrow 2 \mathrm{Fe}+3 \mathrm{CO}_{2}$$
Suppose that $1.64 \times 10^{3} \mathrm{kg}$ of $\mathrm{Fe}$ is obtained from a $2.62 \times$ $10^{3}-\mathrm{kg}$ sample of $\mathrm{Fe}_{2} \mathrm{O}_{3}$. Assuming that the reaction goes to completion, what is the percent purity of $\mathrm{Fe}_{2} \mathrm{O}_{3}$ in the original sample?

Daniel Kim
Daniel Kim
Numerade Educator
05:40

Problem 123

Carbon dioxide $\left(\mathrm{CO}_{2}\right)$ is the gas that is mainly responsible for global warming (the greenhouse effect). The burning of fossil fuels is a major cause of the increased concentration of $\mathrm{CO}_{2}$ in the atmosphere. Carbon dioxide is also the end product of metabolism (see Sample Problem 3.4). Using glucose as an example of food, calculate the annual human production of $\mathrm{CO}_{2}$ in grams, assuming that each person consumes $5.0 \times 10^{2} \mathrm{g}$ of glucose per day, that the world's population is 6.5 billion, and that there are 365 days in a year.

Daniel Kim
Daniel Kim
Numerade Educator
04:40

Problem 124

Carbohydrates are compounds containing carbon, hydrogen, and oxygen in which the hydrogen to oxygen ratio is $2: 1 .$ A certain carbohydrate contains 40.0 percent carbon by mass. Calculate the empirical and molecular formulas of the compound if the approximate molar mass is $178 \mathrm{g}$

Daniel Kim
Daniel Kim
Numerade Educator
02:56

Problem 125

Which of the following has the greater mass: $0.72 \mathrm{g}$ of $\mathrm{O}_{2}$ or 0.0011 mole of chlorophyll $\left(\mathrm{C}_{55} \mathrm{H}_{72} \mathrm{MgN}_{4} \mathrm{O}_{5}\right) ?$

Daniel Kim
Daniel Kim
Numerade Educator
02:54

Problem 126

Analysis of a metal chloride $\mathrm{XCl}_{3}$ shows that it contains 67.2 percent Cl by mass. Calculate the molar mass of $X$, and identify the element.

Daniel Kim
Daniel Kim
Numerade Educator
04:06

Problem 127

Hemoglobin $\left(\mathrm{C}_{2952} \mathrm{H}_{4664} \mathrm{N}_{812} \mathrm{O}_{832} \mathrm{S}_{8} \mathrm{Fe}_{4}\right)$ is the oxygen carrier in
blood. (a) Calculate its molar mass. (b) An average adult has about $5.0 \mathrm{L}$ of blood. Every milliliter of blood has approximately $5.0 \times 10^{9}$ erythrocytes, or red blood cells, and every red blood cell has about $2.8 \times 10^{8}$ hemoglobin molecules. Calculate the mass of hemoglobin molecules in grams in an average adult.

Daniel Kim
Daniel Kim
Numerade Educator
02:03

Problem 128

Myoglobin stores oxygen for metabolic processes in muscle. Chemical analysis shows that it contains 0.34 percent Fe by mass. What is the molar mass of myoglobin? (There is one Fe atom per molecule.)

Daniel Kim
Daniel Kim
Numerade Educator
10:00

Problem 129

Calculate the number of cations and anions in each of the following compounds: (a) $8.38 \mathrm{g}$ of $\mathrm{KBr}$, (b) $5.40 \mathrm{g}$ of $\mathrm{Na}_{2} \mathrm{SO}_{4}$
(c) $7.45 \mathrm{g}$ of $\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}$.

Daniel Kim
Daniel Kim
Numerade Educator
17:57

Problem 130

A mixture of $\mathrm{NaBr}$ and $\mathrm{Na}_{2} \mathrm{SO}_{4}$ contains 29.96 percent $\mathrm{Na}$ by mass. Calculate the percent by mass of each compound in the mixture.

Shazia Naz
Shazia Naz
Numerade Educator
05:39

Problem 131

Aspirin or acetyl salicylic acid is synthesized by combining salicylic acid with acetic anhydride:
$$\mathrm{C}_{7} \mathrm{H}_{6} \mathrm{O}_{3}+\mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{3} \longrightarrow \mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4}+\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$$
(a) How much salicylic acid is required to produce $0.400 \mathrm{g}$ of aspirin (about the content in a tablet), assuming acetic anhydride is present in excess? (b) Calculate the amount of salicylic acid needed if only 74.9 percent of salicylic is converted to aspirin.
(c) In one experiment, 9.26 g of salicylic acid reacts with $8.54 \mathrm{g}$ of acetic anhydride. Calculate the theoretical yield of aspirin and the percent yield if only $10.9 \mathrm{g}$ of aspirin is produced.

Katherine Pohly
Katherine Pohly
Numerade Educator
03:17

Problem 132

Calculate the percent composition by mass of all the elements in calcium phosphate $\left[\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}\right],$ a major component of bone.

Daniel Kim
Daniel Kim
Numerade Educator
06:58

Problem 133

Lysine, an essential amino acid in the human body, contains $\mathrm{C}$ H, O, and N. In one experiment, the complete combustion of $2.175 \mathrm{g}$ of lysine gave $3.94 \mathrm{g} \mathrm{CO}_{2}$ and $1.89 \mathrm{g} \mathrm{H}_{2} \mathrm{O} .$ In a separate
experiment, $1.873 \mathrm{g}$ of lysine gave $0.436 \mathrm{g} \mathrm{NH}_{3}$. (a) Calculate the empirical formula of lysine. (b) The approximate molar mass of lysine is $150 \mathrm{g} .$ What is the molecular formula of the compound?

Adriano Chikande
Adriano Chikande
Numerade Educator
02:32

Problem 134

Does 1 g of hydrogen molecules contain as many H atoms as 1 g of hydrogen atoms?

Daniel Kim
Daniel Kim
Numerade Educator
01:28

Problem 135

Avogadro's number has sometimes been described as a conversion factor between amu and grams. Use the fluorine atom $(19.00 \mathrm{amu})$ as an example to show the relationship between the atomic mass unit and the gram.

Daniel Kim
Daniel Kim
Numerade Educator
02:37

Problem 136

The natural abundances of the two stable isotopes of hydrogen (hydrogen and deuterium) are 99.99 percent $_{1}^{1} \mathrm{H}$ and 0.01 percent
i. $\mathrm{H}$. Assume that water exists as either $\mathrm{H}_{2} \mathrm{O}$ or $\mathrm{D}_{2} \mathrm{O}$. Calculate the number of $\mathrm{D}_{2} \mathrm{O}$ molecules in exactly $400 \mathrm{mL}$ of water (density $1.00 \mathrm{g} / \mathrm{mL})$.

Daniel Kim
Daniel Kim
Numerade Educator
02:14

Problem 137

In the formation of carbon monoxide, $\mathrm{CO}$, it is found that $2.445 \mathrm{g}$ of carbon combine with $3.257 \mathrm{g}$ of oxygen. What is the atomic mass of oxygen if the atomic mass of carbon is 12.01 amu?

Daniel Kim
Daniel Kim
Numerade Educator
01:14

Problem 138

What mole ratio of molecular chlorine (Cl,) to molecular oxygen
$\left(\mathrm{O}_{2}\right)$ would result from the breakup of the compound $\mathrm{Cl}_{2} \mathrm{O}_{7}$ into its constituent elements?

Daniel Kim
Daniel Kim
Numerade Educator
04:24

Problem 139

Which of the following substances contains the greatest mass of chlorine: (a) $5.0 \mathrm{g} \mathrm{Cl}_{2},$ (b) $60.0 \mathrm{g} \mathrm{NaClO}_{3},$ (c) $0.10 \mathrm{mol} \mathrm{KCl}$
(d) $30.0 \mathrm{g} \mathrm{MgCl}_{2},$ (e) $0.50 \mathrm{mol} \mathrm{Cl}_{2}$ ?

Crystal Wang
Crystal Wang
Numerade Educator
05:01

Problem 140

A compound made up of $\mathrm{C}, \mathrm{H},$ and $\mathrm{Cl}$ contains 55.0 percent $\mathrm{Cl}$ by mass. If $9.00 \mathrm{g}$ of the compound contain $4.19 \times 10^{23} \mathrm{H}$ atoms, what is the empirical formula of the compound?

Daniel Kim
Daniel Kim
Numerade Educator
04:41

Problem 141

Platinum forms two different compounds with chlorine. One contains 26.7 percent $\mathrm{Cl}$ by mass, and the other contains 42.1 percent Cl by mass. Determine the empirical formulas of the two compounds.

Daniel Kim
Daniel Kim
Numerade Educator
04:12

Problem 142

Heating $2.40 \mathrm{g}$ of the oxide of metal $\mathrm{X}$ (molar mass of $\mathrm{X}=$ $55.9 \mathrm{g} / \mathrm{mol})$ in carbon monoxide (CO) yields the pure metal and carbon dioxide. The mass of the metal product is 1.68 g. From the data given, show that the simplest formula of the oxide is $\mathrm{X}_{2} \mathrm{O}_{3}$ and write a balanced equation for the reaction.

Daniel Kim
Daniel Kim
Numerade Educator
05:30

Problem 143

A compound $X$ contains 63.3 percent manganese $(\mathrm{Mn})$ and 36.7 percent O by mass. When $X$ is heated, oxygen gas is evolved and a new compound $Y$ containing 72.0 percent $M n$ and 28.0 percent
O is formed. (a) Determine the empirical formulas of $X$ and $Y$.
(b) Write a balanced equation for the conversion of X to Y.

Daniel Kim
Daniel Kim
Numerade Educator
01:19

Problem 144

The formula of a hydrate of barium chloride is $\mathrm{BaCl}_{2} \cdot x \mathrm{H}_{2} \mathrm{O}$. If 1.936 g of the compound gives 1.864 g of anhydrous BaSO_upon treatment with sulfuric acid, calculate the value of $x$

Kratika Bhadauria
Kratika Bhadauria
Numerade Educator
04:03

Problem 145

It is estimated that the day Mt. St. Helens erupted (May 18 ,
1980)$,$ about $4.0 \times 10^{5}$ tons of $\mathrm{SO}_{2}$ were released into the atmosphere. If all the $S O_{2}$ were eventually converted to sulfuric acid, how many tons of $\mathrm{H}_{2} \mathrm{SO}_{4}$ were produced?

Daniel Kim
Daniel Kim
Numerade Educator
03:53

Problem 146

A mixture of $\mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O}$ and $\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}$ is heated until
all the water is lost. If 5.020 g of the mixture gives 2.988 g of the anhydrous salts, what is the percent by mass of $\mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O}$ in the mixture?

Shazia Naz
Shazia Naz
Numerade Educator
04:10

Problem 147

When $0.273 \mathrm{g}$ of $\mathrm{Mg}$ is heated strongly in a nitrogen $\left(\mathrm{N}_{2}\right)$ atmosphere, a chemical reaction occurs. The product of the reaction weighs 0.378 g. Calculate the empirical formula of the compound containing Mg and N. Name the compound.

Daniel Kim
Daniel Kim
Numerade Educator
09:51

Problem 148

A mixture of methane $\left(\mathrm{CH}_{4}\right)$ and ethane $\left(\mathrm{C}_{2} \mathrm{H}_{6}\right)$ of mass $13.43 \mathrm{g}$ is completely burned in oxygen. If the total mass of $\mathrm{CO}_{2}$ and $\mathrm{H}_{2} \mathrm{O}$ produced is $64.84 \mathrm{g},$ calculate the fraction of $\mathrm{CH}_{4}$ in the mixture.

Shazia Naz
Shazia Naz
Numerade Educator
06:20

Problem 149

Leaded gasoline contains an additive to prevent engine "knocking." On analysis, the additive compound is found to contain carbon, hydrogen, and lead (Pb) (hence, "leaded gasoline"). When $51.36 \mathrm{g}$ of this compound are burned in an apparatus such as that shown in Figure $3.5,55.90 \mathrm{g}$ of $\mathrm{CO}_{2}$ and $28.61 \mathrm{g}$ of $\mathrm{H}_{2} \mathrm{O}$ are produced. Determine the empirical formula of the gasoline additive.

Daniel Kim
Daniel Kim
Numerade Educator
05:51

Problem 150

Because of its detrimental effect on the environment, the lead compound described in Problem 3.149 has been replaced in recent years by methyl tert-butyl ether (a compound of $\mathrm{C}, \mathrm{H}$, and $\mathrm{O}$ ) to enhance the performance of gasoline. (As of 1999 , this compound is also being phased out because of its contamination of drinking water.) When $12.1 \mathrm{g}$ of the compound is burned in an apparatus like the one shown in Figure $3.5,30.2 \mathrm{g}$ of $\mathrm{CO}_{2}$ and $14.8 \mathrm{g}$ of $\mathrm{H}_{2} \mathrm{O}$ are formed. What is the empirical formula of the compound?

Daniel Kim
Daniel Kim
Numerade Educator
05:52

Problem 151

Suppose you are given a cube made of magnesium (Mg) metal of edge length $1.0 \mathrm{cm} .$ (a) Calculate the number of $\mathrm{Mg}$ atoms in the cube. (b) Atoms are spherical in shape. Therefore, the Mg atoms in the cube cannot fill all the available space. If only 74 percent of the space inside the cube is taken up by Mg atoms, calculate the radius in picometers of an $\mathrm{Mg}$ atom. (The density of $\mathrm{Mg}$ is $\left.1.74 \mathrm{g} / \mathrm{cm}^{3}, \text { and the volume of a sphere of radius } r \text { is } \frac{4}{3} \pi r^{3} .\right)$

Daniel Kim
Daniel Kim
Numerade Educator
03:58

Problem 152

A certain sample of coal contains 1.6 percent sulfur by mass. When the coal is burned, the sulfur is converted to sulfur dioxide. To prevent air pollution, this sulfur dioxide is treated with calcium oxide (CaO) to form calcium sulfite (CaSO $_{3}$ ). Calculate the daily mass (in kilograms) of $\mathrm{CaO}$ needed by a power plant that uses $6.60 \times 10^{6} \mathrm{kg}$ of coal per day.

Daniel Kim
Daniel Kim
Numerade Educator
02:58

Problem 153

Air is a mixture of many gases. However, in calculating its molar mass we need consider only the three major components: nitrogen, oxygen, and argon. Given that one mole of air at sea level is made up of 78.08 percent nitrogen, 20.95 percent oxygen, and 0.97 percent argon, what is the molar mass of air?

Daniel Kim
Daniel Kim
Numerade Educator
05:04

Problem 154

A die has an edge length of $1.5 \mathrm{cm}$. (a) What is the volume of one mole of such dice? (b) Assuming that the mole of dice could be packed in such a way that they were in contact with one another, forming stacking layers covering the entire surface of Earth, calculate the height in meters the layers would extend outward. [The radius ( $r$ ) of Earth is $6371 \mathrm{km}$, and the area of a sphere is $\left.4 \pi r^{2} \cdot\right]$

Daniel Kim
Daniel Kim
Numerade Educator
02:33

Problem 155

The following is a crude but effective method for estimating the order of magnitude of Avogadro's number using stearic acid $\left(\mathrm{C}_{18} \mathrm{H}_{36} \mathrm{O}_{2}\right) .$ When stearic acid is added to water, its molecules collect at the surface and form a monolayer; that is, the layer is only one molecule thick. The cross-sectional area of each stearic acid molecule has been measured to be $0.21 \mathrm{nm}^{2} .$ In one experiment it is found that $1.4 \times 10^{-4} \mathrm{g}$ of stearic acid is needed to form a monolayer over water in a dish of diameter $20 \mathrm{cm}$. Based on these measurements, what is Avogadro's number? (The area of a circle of radius $r$ is $\pi r^{2}$.)

Crystal Wang
Crystal Wang
Numerade Educator
21:37

Problem 156

Octane $\left(\mathrm{C}_{8} \mathrm{H}_{18}\right)$ is a component of gasoline. Complete combustion of octane yields $\mathrm{H}_{2} \mathrm{O}$ and $\mathrm{CO}_{2}$. Incomplete combustion produces $\mathrm{H}_{2} \mathrm{O}$ and $\mathrm{CO},$ which not only reduces the efficiency of the engine using the fuel but is also toxic. In a certain test run, 1.000 gallon (gal) of octane is burned in an engine. The total mass of $\mathrm{CO}$, $\mathrm{CO}_{2},$ and $\mathrm{H}_{2} \mathrm{O}$ produced is $11.53 \mathrm{kg}$. Calculate the efficiency of the process; that is, calculate the fraction of octane converted to $\mathrm{CO}_{2} .$ The density of octane is $2.650 \mathrm{kg} / \mathrm{gal}$

Shazia Naz
Shazia Naz
Numerade Educator
03:56

Problem 157

Industrially, hydrogen gas can be prepared by combining propane $\operatorname{gas}\left(\mathrm{C}_{3} \mathrm{H}_{8}\right)$ with steam at about $400^{\circ} \mathrm{C} .$ The products are carbon monoxide (CO) and hydrogen gas ( $\mathrm{H}_{2}$ ). (a) Write a balanced equation for the reaction. (b) How many kilograms of $\mathrm{H}_{2}$ can be obtained from $2.84 \times 10^{3} \mathrm{kg}$ of propane?

Daniel Kim
Daniel Kim
Numerade Educator
03:28

Problem 158

A reaction having a 90 percent yield may be considered a successful experiment. However, in the synthesis of complex molecules such as chlorophyll and many anticancer drugs, a chemist often has to carry out multiple-step syntheses. What is the overall percent yield for such a synthesis, assuming it is a 30-step reaction with a 90 percent yield at each step?

Cheryl Glor
Cheryl Glor
Numerade Educator
05:55

Problem 159

Potash is any potassium mineral that is used for its potassium content. Most of the potash produced in the United States goes into fertilizer. The major sources of potash are potassium chloride (KCl) and potassium sulfate ( $\mathrm{K}_{2} \mathrm{SO}_{4}$ ). Potash production is often reported as the potassium oxide $\left(\mathrm{K}_{2} \mathrm{O}\right)$ equivalent or the amount of $\mathrm{K}_{2} \mathrm{O}$ that could be made from a given mineral. (a) If $\mathrm{KCl}$ costs $\$ 0.55$ per $\mathrm{kg}$, for what price (dollar per $\mathrm{kg}$ ) must $\mathrm{K}_{2} \mathrm{SO}_{4}$ be sold in order to supply the same amount of potassium on a per dollar basis? (b) What mass (in kg) of $\mathrm{K}_{2} \mathrm{O}$ contains the same number of moles of $\mathrm{K}$ atoms as $1.00 \mathrm{kg}$ of $\mathrm{KCl}$ ?

Daniel Kim
Daniel Kim
Numerade Educator
20:05

Problem 160

A $21.496-\mathrm{g}$ sample of magnesium is burned in air to form magnesium oxide and magnesium nitride. When the products are treated with water, $2.813 \mathrm{g}$ of gaseous ammonia is generated. Calculate the amounts of magnesium nitride and magnesium oxide formed.

Shazia Naz
Shazia Naz
Numerade Educator
05:06

Problem 161

A certain metal M forms a bromide containing 53.79 percent $\mathrm{Br}$ by mass. What is the chemical formula of the compound?

Daniel Kim
Daniel Kim
Numerade Educator
06:47

Problem 162

A sample of iron weighing $15.0 \mathrm{g}$ was heated with potassium chlorate $\left(\mathrm{KC} 1 \mathrm{O}_{3}\right)$ in an evacuated container. The oxygen generated from the decomposition of $\mathrm{KClO}_{3}$ converted some of the Fe to $\mathrm{Fe}_{2} \mathrm{O}_{3}$. If the combined mass of $\mathrm{Fe}$ and $\mathrm{Fe}_{2} \mathrm{O}_{3}$ was 17.9 g, calculate the mass of $\mathrm{Fe}_{2} \mathrm{O}_{3}$ formed and the mass of $\mathrm{KClO}_{3}$ decomposed.

Daniel Kim
Daniel Kim
Numerade Educator
24:34

Problem 163

A sample containing $\mathrm{NaCl}, \mathrm{Na}_{2} \mathrm{SO}_{4},$ and $\mathrm{NaNO}_{3}$ gives the following elemental analysis: 32.08 percent $\mathrm{Na}, 36.01$ percent $\mathrm{O}$ 19.51 percent Cl. Calculate the mass percent of each compound in the sample.

Shazia Naz
Shazia Naz
Numerade Educator