• Home
  • Textbooks
  • World of Chemistry
  • Chemical Composition

World of Chemistry

Steven S.Zumdahl, Susan L.Zumdahl, Donald J.DeCoste

Chapter 6

Chemical Composition - all with Video Answers

Educators

+ 10 more educators

Chapter Questions

01:56

Problem 1

Merchants usually sell small nuts, washers, and bolts by weight (like jelly beans!) rather than by individually counting the items. Suppose a particular type of washer weighs 0.110 g on the
average. What would 100 such washers weigh? How many washers would there be in 100 g of washers?

David Collins
David Collins
Numerade Educator
03:03

Problem 2

A particular small laboratory cork weighs 1.63 g, whereas a rubber lab stopper of the same size weighs 4.31 g. How many corks would there be in 500 g of such corks? How many rubber stoppers would there be in 500 g of similar stoppers? How many grams of rubber stoppers would be needed to contain the same number of stoppers as there are corks in 1.00 kg of corks?

Angelina Chavez
Angelina Chavez
Numerade Educator
View

Problem 3

Define the amu. What is one amu equivalent to in grams?

Susan Hallstrom
Susan Hallstrom
Numerade Educator
00:20

Problem 4

Why do we use the average atomic mass of the elements when performing calculations?

Angelina Chavez
Angelina Chavez
Numerade Educator
02:07

Problem 5

Using average atomic masses for each of the following elements (see the table in the inside
front cover of this book), calculate the mass, in amu, of each of the following samples.
a. 635 atoms of hydrogen
b. $1.261 \times 10^{4}$ atoms of tungsten
c. 42 atoms of potassium
d. $7.213 \times 10^{23}$ atoms of nitrogen
e. 891 atoms of iron

Angelina Chavez
Angelina Chavez
Numerade Educator
03:30

Problem 6

Using average atomic masses for each of the following elements (see the table in the inside front cover of this book), calculate the number of atoms present in each of the following samples.
a. 10.81 amu of boron
b. 320.7 amu of sulfur
c. $19,697$ amu of gold
d. $19,695$ amu of xenon
e. 3588.3 amu of aluminum

Jesse Leeder
Jesse Leeder
Numerade Educator
01:36

Problem 7

If an average atom of sulfur weighs 32.07 amu, how many sulfur atoms are contained in a
sample with mass 8274 amu? What is the mass of $5.213 \times 10^{24}$ sulfur atoms?

Angelina Chavez
Angelina Chavez
Numerade Educator
00:48

Problem 8

In 24.02 g of carbon, there are ______ carbon atoms.

Ronald Prasad
Ronald Prasad
Numerade Educator
00:18

Problem 9

A sample equal to the atomic mass of an element in grams contains ______ atoms.

Angelina Chavez
Angelina Chavez
Numerade Educator
03:38

Problem 10

What mass of calcium metal contains the same number of atoms as 12.16 g of magnesium?
What mass of calcium metal contains the same number of atoms as 24.31 g of magnesium?

Chareen Guzman
Chareen Guzman
Numerade Educator
03:51

Problem 11

What mass of cobalt contains the same number of atoms as 57.0 g of fluorine?

Cathy Geisel
Cathy Geisel
Numerade Educator
00:48

Problem 12

Calculate the average mass in grams of 1 atom of oxygen.

Angelina Chavez
Angelina Chavez
Numerade Educator
01:59

Problem 13

Which weighs more, 0.50 mol of oxygen atoms or 4 mol of hydrogen atoms?

Michelle Stauffer
Michelle Stauffer
Numerade Educator
03:52

Problem 14

Using the average atomic masses given in the inside front cover of this book, calculate the
number of moles of each element in samples with the following masses.
a. 26.2 g of gold
b. 41.5 g of calcium
c. 335 mg of barium
d. $1.42 \times 10^{23}$ g of palladium
e. $3.05 \times 10^{25} \mathrm{mg}$ of nickel
f. 1.00 lb of iron
g. 12.01 g of carbon

Angelina Chavez
Angelina Chavez
Numerade Educator
03:31

Problem 15

Using the average atomic masses given in the inside front cover of this book, calculate the mass in grams of each of the following samples.
a. 2.00 mol of iron
b. 0.521 mol of nickel
c. $1.23 \times 10^{-3}$ mol of platinum
d. 72.5 mol of lead
e. 0.00102 mol of magnesium
f. $4.87 \times 10^{3}$ mol of aluminum
g. 211.5 mol of lithium
h. $1.72 \times 10^{-6}$ mol of sodium

Angelina Chavez
Angelina Chavez
Numerade Educator
05:02

Problem 16

Using the average atomic masses given in the inside front cover of this book, calculate the indicated quantities.
a. the number of cobalt atoms in 0.00103 g of cobalt atoms in
b. the number of cobalt atoms in 0.00103 mol of cobalt
c. the number of moles of cobalt in 2.75 $\mathrm{g}$ of cobalt
d. the number of moles of cobalt represented by $5.99 \times 10^{21}$ cobalt atoms
e. the mass of 4.23 mol of cobalt
f. the number of cobalt atoms in 4.23 mol of cobalt
g. the number of cobalt atoms in 4.23 $g$ of cobalt

David Collins
David Collins
Numerade Educator
00:13

Problem 17

The ________ of a substance is the mass (in grams) of 1 mol of the substance.

Angelina Chavez
Angelina Chavez
Numerade Educator
00:15

Problem 18

The molar mass of a substance can be obtained by ________ the atomic masses of the component atoms.

Angelina Chavez
Angelina Chavez
Numerade Educator
04:07

Problem 19

Calculate the molar mass for each of the following substances.
a. sodium nitride, $\mathrm{Na}_{3} \mathrm{N}$
b. carbon disulfide, $\mathrm{CS}_{2}$
c. ammonium bromide, $\mathrm{NH}_{4} \mathrm{Br}$
d. ethyl alcohol, C_ $\mathrm{H}_{5} \mathrm{OH}$
e. sulfurous acid, $\mathrm{H}_{2} \mathrm{SO}_{3}$
f. sulfuric acid, $\mathrm{H}_{2} \mathrm{SO}_{4}$

Angelina Chavez
Angelina Chavez
Numerade Educator
04:12

Problem 20

Calculate the molar mass for each of the following substances.
a. barium perchlorate
b. magnesium sulfate
c. lead(II) chloride
d. copper(II) nitrate
e. tin(IV) chloride
f. phenol, $\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{O}$

Angelina Chavez
Angelina Chavez
Numerade Educator
03:10

Problem 21

Calculate the number of moles of the indicated substance in each of the following samples.
a. 49.2 mg of sulfur trioxide
b. $7.44 \times 10^{4} \mathrm{kg}$ of lead(IV) oxide
c. 59.1 $\mathrm{g}$ of chloroform, CHCl_
d. 3.27 $\mathrm{mg}$ of trichloroethane, $\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{Cl}_{3}$
e. 4.01 $\mathrm{g}$ of lithium hydroxide

Angelina Chavez
Angelina Chavez
Numerade Educator
02:38

Problem 22

Calculate the number of moles of the indicated substance in each of the following samples.
a. $4.26 \times 10^{-3} \mathrm{g}$ of sodium dihydrogen phosphate
b. 521 $\mathrm{g}$ of copper(I) chloride
c. 151 $\mathrm{kg}$ of iron
d. 8.76 $\mathrm{g}$ of strontium fluoride
e. $1.26 \times 10^{4} \mathrm{g}$ of aluminum

Angelina Chavez
Angelina Chavez
Numerade Educator
02:32

Problem 23

Calculate the mass in grams of each of the following samples.
a. 1.50 mol of aluminum iodide
b. $1.91 \times 10^{-3}$ mol of benzene, $\mathrm{C}_{6} \mathrm{H}_{6}$
c. 4.00 mol of glucose, $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}$
d. $4.56 \times 10^{5}$ mol of ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$
e. 2.27 $\mathrm{mol}$ of calcium nitrate

Angelina Chavez
Angelina Chavez
Numerade Educator
02:34

Problem 24

Calculate the mass in grams of each of the following samples.
a. $1.27 \times 10^{-3}$ mol of carbon dioxide
b. $4.12 \times 10^{3}$ mol of nitrogen trichloride
c. 0.00451 mol of ammonium nitrate
d. 18.0 mol of water
e. 62.7 mol of copper (II) sulfate

Angelina Chavez
Angelina Chavez
Numerade Educator
03:37

Problem 25

Calculate the number of molecules present in each of the following samples.
a. 6.37 mol of carbon monoxide
b. 6.37 g of carbon monoxide
c. $2.62 \times 10^{-6}$ of water
d. $2.62 \times 10^{-6}$ mol of water
e. 5.23 g of benzene, $\mathrm{C}_{6} \mathrm{H}_{6}$

Ronald Prasad
Ronald Prasad
Numerade Educator
02:50

Problem 26

Calculate the number of moles of sulfur atoms present in each of the following samples.
a. 2.01 g of sodium sulfate
b. 2.01 g of sodium sulfite
c. 2.01 g of sodium sulfide
d. 2.01 g of sodium thiosulfate, $\mathrm{Na}_{2} \mathrm{S}_{2} \mathrm{O}_{3}$

Angelina Chavez
Angelina Chavez
Numerade Educator
15:09

Problem 27

Calculate the percent by mass of each element in the following compounds
a. sodium sulfate
b. sodium sulfate
c. sodium sulfite
d. sodium thiosulfate, $\mathrm{Na}_{2} \mathrm{S}_{2} \mathrm{O}_{3}$
e. potassium phosphate
f. potassium hydrogen phosphate
g. potassium dihydrogen phosphate
h. potassium phosphide.

Temi Ajayi
Temi Ajayi
Numerade Educator
08:13

Problem 28

Calculate the percent by mass of the element listed first in the formulas for each of the following compounds.
a. copper(II) bromide, CuBr $_{2}$
b. copper (I) bromide, CuBr
c. iron(II) chloride, FeCl $_{2}$
d. iron(III) chloride, $\mathrm{FeCl}_{3}$
e. cobalt(II) iodide, $\mathrm{CoI}_{2}$
f. cobalt(III) iodide, $\mathrm{CoI}_{3}$
g. $\operatorname{tin}(\mathrm{II})$ oxide, $\mathrm{SnO}$
h. $\operatorname{tin}(\mathrm{IV})$ oxide, $\mathrm{SnO}_{2}$

Abdel Osman
Abdel Osman
Numerade Educator
08:13

Problem 29

Calculate the percent by mass of the element listed first in the formulas for each of the following compounds.
a. adipic acid, $\mathrm{C}_{6} \mathrm{H}_{10} \mathrm{O}_{4}$
b. ammonium nitrate, $\mathrm{NH}_{4} \mathrm{NO}_{3}$
c. caffeine, $\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{N}_{4} \mathrm{O}_{2}$
d. chlorine dioxide, $\mathrm{ClO}_{2}$
e. cyclohexanol, $\mathrm{C}_{6} \mathrm{H}_{11} \mathrm{OH}$
f. dextrose, $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}$
g. eicosane, $\mathrm{C}_{20} \mathrm{H}_{42}$
h. ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$

Abdel Osman
Abdel Osman
Numerade Educator
08:16

Problem 30

For each of the following ionic substances, calculate the percentage of the overall molar
mass of the compound that is represented by the positive ions the compound contains.
a. ammonium chloride
b. copper(II) sulfate
c. gold(III) chloride
d. silver nitrate

Abdel Osman
Abdel Osman
Numerade Educator
01:12

Problem 31

What experimental evidence about a new compound must be known before its formula can be determined?

David Collins
David Collins
Numerade Educator
02:05

Problem 32

What does the empirical formula of a compound represent? How does the molecular formula differ
from the empirical formula?

Abdel Osman
Abdel Osman
Numerade Educator
02:34

Problem 33

Give the empirical formula that corresponds to each of the following molecular formulas.
a. sodium peroxide, $\mathrm{Na}_{2} \mathrm{O}_{2}$
b. terephthalic acid, $\mathrm{C}_{8} \mathrm{H}_{6} \mathrm{O}_{4}$
c. phenobarbital, $\mathrm{C}_{12} \mathrm{H}_{12} \mathrm{N}_{2} \mathrm{O}_{3}$
d. $1,4$ -dichloro- 2 -butene, $\mathrm{C}_{4} \mathrm{H}_{6} \mathrm{Cl}_{2}$

Chareen Guzman
Chareen Guzman
Numerade Educator
02:54

Problem 34

Which of the following pairs of compounds have the same empirical formula?
a. acetylene, $\mathrm{C}_{2} \mathrm{H}_{2}$ , and benzene, $\mathrm{C}_{6} \mathrm{H}_{6}$
b. ethane, $\mathrm{C}_{2} \mathrm{H}_{6}$ , and butane, $\mathrm{C}_{4} \mathrm{H}_{10}$
c. nitrogen dioxide, $\mathrm{NO}_{2}$ , and dinitrogen
d. diphenyl ether, $\mathrm{C}_{12} \mathrm{H}_{10} \mathrm{O}$ , and phenol,
$\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH}$

Abdel Osman
Abdel Osman
Numerade Educator
02:27

Problem 35

A new compound has been prepared. A 0.4791-g sample was analyzed and was found to contain the following masses of elements: carbon, 0.1929 g hydrogen, 0.01079 g oxygen, 0.08566 g chlorine, 0.1898 g Determine the empirical formula of the new compound.

Abdel Osman
Abdel Osman
Numerade Educator
02:29

Problem 36

In an experiment, a 2.514-g sample of calcium was heated in a stream of pure oxygen, and was
found to increase in mass by 1.004 g. Calculate the empirical formula of calcium oxide.

Abdel Osman
Abdel Osman
Numerade Educator
02:40

Problem 37

A compound has the following percentages by mass: barium, 58.84%; sulfur, 13.74%; oxygen, 27.43%. Determine the empirical formula of the compound.

Abdel Osman
Abdel Osman
Numerade Educator
02:12

Problem 38

If a 1.271-g sample of aluminum metal is heated in a chlorine gas atmosphere, the mass of aluminum chloride produced is 6.280 g. Calculate the empirical formula of aluminum chloride.

Alexandra Grace
Alexandra Grace
Numerade Educator
03:03

Problem 39

If cobalt metal is mixed with excess sulfur and heated strongly, a sulfide is produced that
contains 55.06% cobalt by mass. Calculate the empirical formula of the sulfide.

Abdel Osman
Abdel Osman
Numerade Educator
01:34

Problem 40

If 2.461 g of metallic calcium is heated in a stream of chlorine gas, 4.353 g of $C l_{2}$ is absorbed in forming the metal chloride. Calculate the empirical formula of calcium chloride.

Abdel Osman
Abdel Osman
Numerade Educator
02:35

Problem 41

If 10.00 g of copper metal is heated strongly in the air, the sample gains 2.52 g of oxygen in
forming an oxide. Determine the empirical formula of this oxide.

Abdel Osman
Abdel Osman
Numerade Educator
02:21

Problem 42

A compound has the following percentage composition by mass: copper, 33.88%; nitrogen, 14.94%; oxygen, 51.18%. Determine the empirical formula of the compound.

Abdel Osman
Abdel Osman
Numerade Educator
02:36

Problem 43

Sodium and nitrogen form two binary compounds. The percentages of the elements in these compounds are:
$$\begin{array}{|c|c|c|c|}\hline \text { Compound } & {\text { Na }} & {\mathrm{N}} \\ \hline 1 & {83.12 \%} & {16.88 \%} \\ \hline 2 & {35.36 \%} & {64.64 \%} \\ \hline\end{array}$$
Calculate the empirical formula of each of the compounds.

Abdel Osman
Abdel Osman
Numerade Educator
01:48

Problem 44

How does the molecular formula of a compound differ from the empirical formula? Can a compound’s empirical and molecular formulas be the same? Explain.

Abdel Osman
Abdel Osman
Numerade Educator
05:01

Problem 45

What information do we need to determine the molecular formula of a compound if we know only the empirical formula?

Temi Ajayi
Temi Ajayi
Numerade Educator
02:27

Problem 46

A compound with the empirical formula $\mathrm{CH}_{2} \mathrm{O}$ was found to have a molar mass between 89 and 91 g. What is the molecular formula of the compound?

Abdel Osman
Abdel Osman
Numerade Educator
04:50

Problem 47

A compound with the empirical formula $\mathrm{CH}_{2}$ was found to have a molar mass of approximately 84 g. What is the molecular formula of the compound?

Temi Ajayi
Temi Ajayi
Numerade Educator
01:56

Problem 48

A compound with the empirical formula $\mathrm{CH}_{4} \mathrm{O}$ was found in a subsequent experiment to have a molar mass of approximately 192 g. What is the molecular formula of the compound?

Abdel Osman
Abdel Osman
Numerade Educator
03:19

Problem 49

A compound having an approximate molar mass of $165-170$ g has the following percentage composition by mass: carbon, 42.87$\%$ ; hydrogen, $3.598 \% ;$ oxygen, 28.55$\%$ ;
nitrogen, 25.00$\%$ . Determine the empirical and molecular formulas of the compound.

Ronald Prasad
Ronald Prasad
Numerade Educator
03:15

Problem 50

A compound consists of $65.45 \% \mathrm{C}, 5.492 \% \mathrm{H}$ , and 29.06$\%$ O on a mass basis and has a molar mass of approximately $110 .$ Determine the molecular formula of the compound.

Abdel Osman
Abdel Osman
Numerade Educator
09:16

Problem 51

Use the periodic table inside the back cover of this text to determine the atomic mass (per
mole) or molar mass of each of the substances in column 1, and find that mass in column 2.
(COLUMN IS NOT AVAILABLE TO COPY)

Abdel Osman
Abdel Osman
Numerade Educator
09:38

Problem 52

Copy and complete the following table.
(TABLE IS NOT AVAILABLE TO COPY)

Abdel Osman
Abdel Osman
Numerade Educator
09:38

Problem 53

Copy and complete the following table.
(TABLE IS NOT AVAILABLE TO COPY)

Abdel Osman
Abdel Osman
Numerade Educator
03:07

Problem 54

A binary compound of magnesium and nitrogen is analyzed, and 1.2791 g of the compound is found to contain 0.9240 g of magnesium. When a second sample of this compound is treated with water and heated, the nitrogen is driven off as ammonia, leaving a compound that contains 60.31% magnesium and 39.69% oxygen by mass. Calculate the empirical formulas of the two magnesium compounds.

Abdel Osman
Abdel Osman
Numerade Educator
07:11

Problem 55

When a 2.118-g sample of copper is heated in an atmosphere in which the amount of oxygen present is restricted, the sample gains 0.2666 g of oxygen in forming a reddish-brown oxide. However, when 2.118 g of copper is heated in a stream of pure oxygen, the sample gains 0.5332 g of oxygen. Calculate the empirical formulas of the two oxides of copper.

Temi Ajayi
Temi Ajayi
Numerade Educator
02:59

Problem 56

A molecule of an organic compound has twice as many hydrogen atoms as carbon atoms, the
same number of oxygen atoms as carbon atoms, and one-eighth as many sulfur atoms as hydrogen atoms. The molar mass of the compound is 152 g/mol. What are the empirical and molecular formulas for this compound?

Abdel Osman
Abdel Osman
Numerade Educator
02:48

Problem 57

Calculate the number of grams of iron that contain the same number of atoms as 2.24 g of cobalt.

Jennifer Hudspeth
Jennifer Hudspeth
Numerade Educator
04:39

Problem 58

Calculate the number of grams of cobalt that contain the same number of atoms as 2.24 g of iron.

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
05:16

Problem 59

A strikingly beautiful copper compound with the common name blue vitriol has the following elemental composition: 25.45$\%$ Cu, $12.84 \% \mathrm{S}, 4.036 \% \mathrm{H}, 57.67 \%$ O. Determine the empirical formula of the compound.

Temi Ajayi
Temi Ajayi
Numerade Educator
02:35

Problem 60

A 0.7221 -g sample of a new compound has been analyzed and found to contain the following masses of elements: carbon, 0.2990 $\mathrm{g}$ ; hydrogen, 0.05849 g; nitrogen, $0.2318 \mathrm{g} ;$
oxygen, 0.1328 g. Calculate the empirical formula of the compound.

Abdel Osman
Abdel Osman
Numerade Educator
05:30

Problem 61

When 4.01 g of mercury is strongly heated in air, the resulting oxide weighs 4.33 g. Calculate the empirical formula of the oxide.

Vishal Sharma
Vishal Sharma
Numerade Educator
02:14

Problem 62

When barium metal is heated in chlorine gas, a binary compound forms that consists of
65.95% Ba and 34.05% Cl by mass. Calculate the empirical formula of the compound.

Abdel Osman
Abdel Osman
Numerade Educator
01:48

Problem 63

A particular compound in the chemistry laboratory is found to contain $7.2 \times 10^{24}$ atoms of
oxygen, 56.0 g of nitrogen, and 4.0 mol of hydrogen. What is its empirical formula?

Abdel Osman
Abdel Osman
Numerade Educator
02:02

Problem 64

The compound $A_{2} O$ is 63.7$\%$ ( a mystery element) and 36.3$\%$ oxygen. What is the identity of element A?

Abdel Osman
Abdel Osman
Numerade Educator
03:47

Problem 65

Find the item in list $\mathrm{B}$ that best explains or completes the statement or question in list A.
List $\mathrm{A}$
(1) 1 amu
(2) 1008 amu
(3) mass of the "average" atom of an element
(4) number of carbon atoms in 12.01 g of carbon
(5) $6.022 \times 10^{23}$ molecules
(6) total mass of all atoms in 1 mol of a compound
(7) smallest whole-number ratio of atoms present in a molecule
(8) formula showing the actual number of atoms present in a molecule
(9) product formed when any carbon-containing compound is burned in $\mathrm{O}_{2}$
(10) have the same empirical formulas, but different molecular formulas
List $B$
(a) $6.022 \times 10^{23}$
(b) atomic mass
(c) mass of 1000 hydrogen atoms
(d) benzene, $\mathrm{C}_{6} \mathrm{H}_{6}$ , and acetylene, $\mathrm{C}_{2} \mathrm{H}_{2}$
(f) carbon dioxide
(f) empirical formula
(f) molecular formula
(i) molar mass
(j) 1 $\mathrm{mol}$

Abdel Osman
Abdel Osman
Numerade Educator