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Chemistry Principles and Reactions

William L Masterton; Cecile N Hurley; Edward J Neth

Chapter 2

Atoms, Molecules, and Ions - all with Video Answers

Educators

Chapter Questions

05:10

Problem 1

State in your own words the law of conservation of mass. State the law in its modern form.

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04:40

Problem 2

State in your own words the law of constant composition.

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01:54

Problem 3

Two basic laws of chemistry are the law of conservation of mass and the law of constant composition. Which of these laws (if any) do the following statements illustrate?
(a) Lavoisier found that when mercury(II) oxide, $\mathrm{HgO},$ decomposes, the total mass of mercury (Hg) and oxygen formed equals the mass of mercury(II) oxide decomposed.
(b) Analysis of the calcium carbonate found in the marble mined in Carrara, Italy, and in the stalactites of the Carlsbad Caverns in New Mexico gives the same value for the percentage of calcium in calcium carbonate.
(c) Hydrogen occurs as a mixture of two isotopes, one of which is twice as heavy as the other.

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01:15

Problem 4

Which of the laws described in Question 3 do the following statements illustrate?
(a) A sealed bag of popcorn has the same mass before and after it is put in a microwave oven. (Assume no breaks develop in the bag.)
(b) Hydrogen has three isotopes. One has a mass number $A$ equal to its atomic number $Z$. In another isotope, $A=2 Z,$ and in a third, $A=3 Z$.
(c) A teaching assistant writes "highly improbable" on a student's report that states that her unknown is $\mathrm{Cu}_{1.3} \mathrm{O}_{1.4}$

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03:30

Problem 5

Who discovered the electron? Describe the experiment that led to the deduction that electrons are negatively charged particles.

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09:16

Problem 6

Who discovered the nucleus? Describe the experiment that led to this discovery.

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01:39

Problem 7

Selenium is widely sold as a dietary supplement. It is advertised to "protect" women from breast cancer. Write the nuclear symbol for naturally occurring selenium. It has 34 protons and 46 neutrons.

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00:46

Problem 8

Yttrium-90 is used in the treatment of cancer, particularly nonHodgkin's lymphoma.
(a) How many protons are there in an atom of Y-90?
(b) How many neutrons?
(c) Write the nuclear symbol $\left({ }_{Z}^{A} X\right)$ for $Y-90$.

Nicole Smina
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00:46

Problem 9

How do the isotopes of $\mathrm{Cu}-63$ and Cu-65 differ from each other? Write nuclear symbols for both.

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Problem 10

Consider two isotopes Fe-54 and Fe-56.
(a) Write the nuclear symbol for both isotopes.
(b) How do they differ from each other?

Ronald Prasad
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01:48

Problem 11

Uranium- 235 is the isotope of uranium commonly used in nuclear power plants. How many
(a) protons are in its nucleus?
(b) neutrons are in its nucleus?
(c) electrons are in a uranium atom?

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02:32

Problem 12

An isotope of americium (Am) with 146 neutrons is used in many smoke alarms.
(a) How many electrons does an atom of americium have?
(b) What is the isotope's mass number $A$ ?
(c) Write its nuclear symbol.

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Problem 13

Consider the following nuclear symbols. How many protons, neutrons, and electrons does each element have? What elements do $\mathrm{R}, \mathrm{T},$ and $\mathrm{X}$ represent?
(a) $\frac{30}{14} R$
(b) $\frac{89 \mathrm{~T}}{39}$
(c) $133 \mathrm{X}$

Ronald Prasad
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01:17

Problem 14

Consider the following nuclear symbols. How many protons, neutrons, and electrons does each element have? What elements do $A, L,$ and $Z$
represent?
(a) $\frac{75}{33} \mathrm{~A}$
(b) $\frac{51}{23} \mathrm{~L}$
(c) $\frac{131}{54} Z$

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06:25

Problem 15

Nuclei with the same mass number but different atomic numbers are called isobars. Consider Ca-40, Ca-41, K-41 and Ar-41.
(a) Which of these are isobars? Which are isotopes?
(b) What do Ca-40 and Ca-41 have in common?
(c) Correct the statement (if it is incorrect): Atoms of Ca-41, K-41, and Ar-41 have the same number of neutrons.

Jennifer Hudspeth
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01:15

Problem 16

See the definition for isobars in Question 15. Consider boron-12, and write the nuclear symbol for
(a) an isobar of boron- 12 with atomic number 6 .
(b) a nucleus with 4 protons and 8 neutrons. Is this nucleus an isotope or an isobar of boron- $12 ?$
(c) a nucleus with 5 protons and 6 neutrons. Is this nucleus an isotope or an isobar of boron- $12 ?$

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04:39

Problem 17

Calculate the mass ratio of a bromine atom to an atom of
(a) neon
(b) calcium
(c) helium

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01:28

Problem 18

Arrange the following in order of increasing mass.
(a) a sodium ion
(b) a selenium atom
(c) a sulfur $\left(\mathrm{S}_{8}\right)$ molecule
(d) a scandium atom

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00:35

Problem 19

Cerium is the most abundant rare earth metal. Pure cerium ignites when scratched by even a soft object. It has four known isotopes: ${ }^{136} \mathrm{Ce}$ (atomic mass $=135.907 \mathrm{amu}),{ }^{138} \mathrm{Ce}$ (atomic mass $\left.=137.905 \mathrm{amu}\right),{ }^{140} \mathrm{Ce}$ (atomic mass $=$
$139.905 \mathrm{amu}$ ), and ${ }^{142} \mathrm{Ce}$ (atomic mass $=141.909 \mathrm{amu}$ ). Ce-140 and Ce-142 are fairly abundant. Which is the more abundant isotope?

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00:32

Problem 20

Consider the three stable isotopes of oxygen with their respective atomic masses: $\mathrm{O}-16(15.9949 \mathrm{amu}), \mathrm{O}-17(16.9993 \mathrm{amu}), \mathrm{O}-18(17.9992 \mathrm{amu}) .$
Which is the most abundant?

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01:09

Problem 21

Gallium has two naturally occurring isotopes: ${ }^{69} \mathrm{Ga}$, with atomic mass $68.9257 \mathrm{amu},$ and ${ }^{71} \mathrm{Ga},$ with atomic mass 70.9249 amu. The percent abundance of ${ }^{69}$ Ga can be estimated to be which of the following?
(a) $0 \%$
(b) $25 \%$
(c) $50 \%$
(d) $75 \%$

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05:30

Problem 22

Rubidium has two naturally occurring isotopes: ${ }^{85} \mathrm{Rb}$ (atomic mass = 84.9118 amu $)$ and ${ }^{87} \mathrm{Rb}$ (atomic mass $=86.9092 \mathrm{amu}$ ). The percent abundance of ${ }^{87} \mathrm{Rb}$ can be estimated to be which of the following?
(a) $0 \%$
(b) $25 \%$
(c) $50 \%$
(d) $75 \%$

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03:56

Problem 23

Strontium has four isotopes with the following masses: 83.9134 amu $(0.56 \%), 85.9094$ amu $(9.86 \%), 86.9089$ amu $(7.00 \%),$ and 87.9056 amu $(82.58 \%) .$ Calculate the average atomic mass of strontium.

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01:32

Problem 24

Silicon is widely used in the semiconductor industry. Its isotopes and abundances are:
$\mathrm{Si}-28$
$\begin{array}{ll}27.977 \mathrm{amu} & 92.34 \%\end{array}$
$\begin{array}{lll}\mathrm{Si}-29 & 28.977 \mathrm{amu} & 4.70 \% \\ \mathrm{Si}-30 & 29.974 \mathrm{amu} & 2.96 \%\end{array}$
What is the average atomic mass of silicon?

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01:29

Problem 25

Naturally occurring silver (Ag) consists of two isotopes. One of the isotopes has a mass of 106.90509 amu and $51.84 \%$ abundance. What is the atomic mass of the other isotope?

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05:25

Problem 26

Copper has two naturally occurring isotopes. Cu-63 has an atomic mass of 62.9296 amu and an abundance of $69.17 \% .$ What is the atomic mass of the second isotope? What is its nuclear symbol?

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02:57

Problem 27

Chromium (average atomic mass $=51.9961$ amu $)$ has four isotopes. Their masses are 49.94605 amu, 51.94051 amu, 52.94065 amu, and 53.93888 amu. The first two isotopes have a total abundance of $87.87 \%$, and the last isotope has an abundance of $2.365 \% .$ What is the abundance of the third isotope? Estimate the abundances of the first two isotopes.

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06:02

Problem 28

Magnesium (average atomic mass $=24.305$ amu) consists of three isotopes with masses 23.9850 amu, 24.9858 amu, and 25.9826 amu. The abundance of the middle isotope is $10.00 \%$. Estimate the abundances of the other isotopes.

Susan Hallstrom
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01:20

Problem 29

Neon consists of three isotopes, $\mathrm{Ne}-20, \mathrm{Ne}-21,$ and $\mathrm{Ne}-22 .$ Their abundances are $90.48 \%, 0.27 \%,$ and $9.22 \%$, respectively. Sketch the mass spectrum for neon.

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09:21

Problem 30

Chlorine has two isotopes, Cl-35 and Cl-37. Their abundances are $75.53 \%$ and $24.47 \%$, respectively. Assume that the only hydrogen isotope present is $\mathrm{H}-1$
(a) How many different HCl molecules are possible?
(b) What is the sum of the mass numbers of the two atoms in each molecule?
(c) Sketch the mass spectrum for HCl if all the positive ions are obtained by removing a single electron from an $\mathrm{HCl}$ molecule.

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04:30

Problem 31

Lead is a heavy metal that remains in the bloodstream, causing mental retardation in children. It is believed that $3 \times 10^{-7} \mathrm{~g}$ of $\mathrm{Pb}$ in $1.00 \mathrm{~mL}$ of blood is a health hazard. For this amount of lead how many atoms of lead are there in one $\mathrm{mL}$ of a child's blood?

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03:47

Problem 32

Silversmiths are warned to limit their exposure to silver in the air to $1 \times 10^{-8} \mathrm{~g} \mathrm{Ag} / \mathrm{L}$ of air in a 40 -hour week. What is the allowed exposure in terms of atoms of $\mathrm{Ag} / \mathrm{L} /$ week?

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04:33

Problem 33

Determine
(a) the number of atoms in $0.185 \mathrm{~g}$ of palladium (Pd).
(b) the mass of 127 protons of palladium.

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02:02

Problem 34

How many protons are in
(a) ten atoms of platinum?
(b) ten grams of platinum?

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04:45

Problem 35

The isotope Si-28 has a mass of 27.977 amu. For ten grams of $\mathrm{Si}-28$, calculate
(a) the number of atoms.
(b) the total number of protons, neutrons, and electrons.

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02:11

Problem 36

Consider an isotope of yttrium, Y-90. This isotope is incorporated into cancer-seeking antibodies so that the cancer can be irradiated by the yttrium and destroyed. How many neutrons are in
(a) twenty-five atoms of yttrium?
(b) one nanogram $\left(10^{-9} \mathrm{~g}\right)$ of yttrium?

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01:48

Problem 37

A cube of sodium has length 1.25 in. How many atoms are in that cube? (Note: $\left.d_{\mathrm{Na}}=0.968 \mathrm{~g} / \mathrm{cm}^{3} .\right)$

Eileen Sullivan
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05:47

Problem 38

A cylindrical piece of pure copper $\left(d=8.92 \mathrm{~g} / \mathrm{cm}^{3}\right)$ has diameter $1.15 \mathrm{~cm}$ and height 4.00 inches. How many atoms are in that cylinder? (Note: the volume of a right circular cylinder of radius $r$ and height $h$ is $\left.V=\pi r^{2} h .\right)$

Dr. Satish Ingale
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00:24

Problem 39

Give the symbols for
(a) potassium
(b) cadmium
(c) aluminum
(d) antimony
(e) phosphorus

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00:45

Problem 40

Name the elements represented by
(a) $\mathrm{S}$
(b) $\mathrm{Sc}$
(c) Se
(d) $\mathrm{Si}$
(e) $\mathrm{Sr}$

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01:20

Problem 41

Classify the elements in Question 39 as metals (main group, transition, or post-transition), nonmetals, or metalloids.

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01:30

Problem 42

Classify the elements in Question 40 as metals (main group, transition, or post-transition), nonmetals, or metalloids.

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00:52

Problem 43

How many metals are in the following groups?
(a) Group 1
(b) Group 13
(c) Group 17

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00:31

Problem 44

How many nonmetals are in the following periods?
(a) period 2
(b) period 4
(c) period 6

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03:32

Problem 45

Which group in the periodic table
(a) has one metalloid and no nonmetals?
(b) has no nonmetals or transition metals?
(c) has no metals or metalloids?

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00:50

Problem 46

Which period of the periodic table
(a) has no metals?
(b) has no nonmetals?
(c) has one post-transition metal and two metalloids?

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00:32

Problem 47

Given the following condensed formulas, write the molecular formulas for the following molecules.
(a) dimethylamine $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}$
(b) propyl alcohol $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{2} \mathrm{OH}$

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00:48

Problem 48

Write the condensed structural formulas and molecular formulas for the
following molecules. The reactive groups are shown in red.

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01:44

Problem 49

Give the number of protons and electrons in
(a) an $\mathrm{N}_{2}$ molecule (identified in 1772 ).
(b) an $\mathrm{N}_{3}^{-}$ unit (synthesized in 1890 ).
(c) an $\mathrm{N}_{5}{ }^{+}$ unit (synthesized in 1999 ).
(d) an $\mathrm{N}_{5} \mathrm{~N}_{5}$ salt (a U.S. Air Force research team's synthesis project).

Susan Hallstrom
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00:54

Problem 50

Give the number of protons and electrons in the following:
(a) $\mathrm{S}_{8}$ molecule.
(b) $\mathrm{SO}_{4}^{2-}$ ion.
(c) $\mathrm{H}_{2} \mathrm{~S}$ molecule.
(d) $\mathrm{S}^{2-}$ ion.

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03:56

Problem 51

Complete the table below. If necessary, use the periodic table.

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03:56

Problem 52

Complete the table below. Use the periodic table if necessary.

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01:14

Problem 53

Classify the following compounds as electrolytes or nonelectrolytes.
(a) potassium chloride, $\mathrm{KCl}$
(b) hydrogen peroxide, $\mathrm{H}_{2} \mathrm{O}_{2}$
(c) methane, $\mathrm{CH}_{4}$
(d) barium nitrate, $\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}$

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02:00

Problem 54

Which (if any) of the following compounds are nonelectrolytes?
(a) citric acid $\left(\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7}\right)$
(b) calcium nitrate, $\mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}$
(c) ammonium carbonate, $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}$
(d) iodine tribromide (IBr $_{3}$ )

Dr. Satish Ingale
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00:50

Problem 55

Write the formulas for the following molecules.
(a) methane
(b) carbon tetraiodide
(c) hydrogen peroxide
(d) nitrogen oxide
(e) silicon dioxide

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00:41

Problem 56

Write the formulas for the following molecules.
(a) water
(b) ammonia
(c) hydrazine
(d) sulfur hexafluoride
(e) phosphorus pentachloride

Nicole Smina
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01:32

Problem 57

Write the names of the following molecules.
(a) $\mathrm{ICl}_{3}$
(b) $\mathrm{N}_{2} \mathrm{O}_{5}$
(c) $\mathrm{PH}_{3}$
(d) $\mathrm{CBr}_{4}$
(e) $\mathrm{SO}_{3}$

Dr. Satish Ingale
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01:14

Problem 58

Write the names of the following molecules.
(a) $\mathrm{Se}_{2} \mathrm{Cl}_{2}$
(b) $\mathrm{CS}_{2}$
(c) $\mathrm{PH}_{3}$
(d) $\mathrm{IF}_{7}$
(e) $\mathrm{P}_{4} \mathrm{O}_{6}$

Nicole Smina
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02:00

Problem 59

Give the formulas of all the compounds containing no ions other than $\mathrm{K}^{+}, \mathrm{Ca}^{2+}, \mathrm{Cl}^{-},$ and $\mathrm{S}^{2-}$

Dr. Satish Ingale
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02:55

Problem 60

Give the formulas of compounds in which
(a) the cation is $\mathrm{Ba}^{2+},$ the anion is $\mathrm{I}^{-}$ or $\mathrm{N}^{3-}$.
(b) the anion is $\mathrm{O}^{2-}$, the cation is $\mathrm{Fe}^{2+}$ or $\mathrm{Fe}^{3+}$.

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01:25

Problem 61

Write the formulas of the following ionic compounds.
(a) iron(III) carbonate
(b) sodium azide $\left(\mathrm{N}_{3}-\right)$
(c) calcium sulfate
(d) copper(I) sulfide
(e) lead(IV) oxide

Nicole Smina
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01:35

Problem 62

Write formulas for the following ionic compounds:
(a) potassium hydrogen phosphate
(b) magnesium nitride
(c) lead(IV) bromide
(d) scandium(III) chloride
(e) barium acetate

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02:05

Problem 63

Write the names of the following ionic compounds.
(a) $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$
(b) $\mathrm{Cu}_{3}\left(\mathrm{PO}_{4}\right)_{2}$
(c) $\mathrm{Ba}\left(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)_{2}$
(d) AlN
(e) $\mathrm{Co}\left(\mathrm{NO}_{3}\right)_{2}$

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01:14

Problem 64

Write the names of the following ionic compounds.
(a) $\mathrm{ScCl}_{3}$
(b) $\mathrm{Sr}(\mathrm{OH})_{2}$
(c) $\mathrm{KMnO}_{4}$
(d) $\mathrm{Rb}_{2} \mathrm{~S}$
(e) $\mathrm{Na}_{2} \mathrm{CO}_{3}$

Nicole Smina
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01:33

Problem 65

Write the names of the following ionic compounds.
(a) $\mathrm{HCl}(a q)$
(b) $\mathrm{HClO}_{3}(a q)$
(c) $\mathrm{Fe}_{2}\left(\mathrm{SO}_{3}\right)_{3}$
(d) $\mathrm{Ba}\left(\mathrm{NO}_{2}\right)_{2}$
(e) $\mathrm{NaClO}$

Dr. Satish Ingale
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01:21

Problem 66

Write formulas for the following ionic compounds.
(a) nitric acid
(b) potassium sulfate
(c) iron(III) perchlorate
(d) aluminum iodate
(e) sulfurous acid

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02:54

Problem 67

Complete the following table.

Bryan Lynn
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02:54

Problem 68

Complete the following table.

Bryan Lynn
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01:26

Problem 69

Write the formulas and names of the following:
(a) An ionic compound whose cation is a transition metal with 25 protons and 22 electrons and whose anion is an oxoanion of nitrogen with two oxygen atoms.
(b) A molecule made up of a metalloid in Group 13 and three atoms of a halogen in period 2 .
(c) An ionic compound made up of an alkaline earth with 20 protons, and an anion with one hydrogen atom, a carbon atom, and 3 oxygen atoms.

Prashant Bana
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01:17

Problem 70

Identify the following elements:
(a) A member of the same period as selenium but with two fewer protons than selenium.
(b) A transition metal in group $6,$ period 6 .
(c) An alkaline earth with 38 protons.
(d) A post-transition metal in group $15 .$

Dr. Satish Ingale
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01:40

Problem 71

Hydrogen-1 can take the form of a molecule, an anion $\left(\mathrm{H}^{-}\right),$ or a cation
$\left(\mathrm{H}^{+}\right)$
(a) How many protons, electrons, and neutrons are in each possible species?
(b) Write the name and formula for the compound formed between hydrogen and a metal in Group 2 with 12 protons.
(c) What is the general name of the aqueous compounds in which hydrogen is a cation?

Nicole Smina
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03:02

Problem 72

A molecule of ethylamine is made up of two carbon atoms, seven hydrogen atoms, and one nitrogen atom.
(a) Write its molecular formula.
(b) The reactive group in ethylamine is $\mathrm{NH}_{2}$. Write its condensed structural formula.

Dr. Satish Ingale
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01:29

Problem 73

Criticize each of the following statements.
(a) In an ionic compound, the number of cations is always the same as the number of anions.
(b) The molecular formula for strontium bromide is $\operatorname{SrBr}_{2}$.
(c) The mass number is always equal to the atomic number.
(d) For any ion, the number of electrons is always more than the number of protons.

Nicole Smina
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01:46

Problem 74

Which of the following statements is/are always true? Never true? Usually true?
(a) Compounds containing chlorine can be either molecular or ionic.
(b) An ionic compound always has at least one metal.
(c) When an element in a molecule has a "di" prefix, it means that the element has a +2 charge.

Dr. Satish Ingale
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07:28

Problem 75

Some brands of salami contain $0.090 \%$ sodium benzoate $\left(\mathrm{NaC}_{7} \mathrm{H}_{5} \mathrm{O}_{2}\right)$ as a preservative. If you eat 6.00 oz of this salami, how many atoms of sodium will you consume, assuming salami contains no other source of that element?

Dr. Satish Ingale
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05:34

Problem 76

Carbon tetrachloride, $\mathrm{CCl}_{4}$, was a popular dry-cleaning agent until it was shown to be carcinogenic. It has a density of $1.589 \mathrm{~g} / \mathrm{cm}^{3} .$ What volume of carbon tetrachloride will contain a total of $6.00 \times 10^{25}$ molecules of $\mathrm{CCl}_{4} ?$

Dr. Satish Ingale
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01:20

Problem 77

Which statements are true?
(a) Neutrons have neither mass nor charge.
(b) Isotopes of an element have an identical number of protons.
(c) C-14 and N-14 have identical neutron/proton ( $n / p^{+}$ ) ratios.
(d) The vertical columns in a periodic table are referred to as "groups."
(e) When an atom loses an electron, it becomes positively charged.

Nicole Smina
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01:53

Problem 78

A student saw the following nuclear symbol for an unknown element:
${ }_{11}^{23} \mathrm{X} .$ Which of the following statements about $\mathrm{X}$ and ${ }_{11}^{23} \mathrm{X}$ are true?
(a) $\mathrm{X}$ is sodium.
(b) $\mathrm{X}$ is vanadium.
(c) $\mathrm{X}$ has 23 neutrons in its nucleus.
(d) $\mathrm{X}^{2+}$ has 13 electrons.
(e) ${ }_{11}^{23} \mathrm{X}$ has a proton/neutron ratio of about 1.1 .

Dr. Satish Ingale
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01:02

Problem 79

Using the laws of constant composition and the conservation of mass, complete the molecular picture of hydrogen molecules $(\bigcirc-\bigcirc)$ reacting with chlorine molecules $(\square-\square)$ to give hydrogen chloride $(\square-\bigcirc)$ molecules.

Nicole Smina
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01:00

Problem 80

Use the law of conservation of mass to determine which numbered box(es) represent(s) the product mixture after the substances in the box at the top of the next column undergo a reaction.

Nicole Smina
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02:07

Problem 81

If squares represent carbon and spheres represent chlorine, make a representation of liquid $\mathrm{CCl}_{4}$.

Dr. Satish Ingale
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01:18

Problem 82

If squares represent $\mathrm{Cl}$ atoms and spheres represent $\mathrm{K}$ atoms, make a representation of a KCl crystal.

Crystal Wang
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02:07

Problem 83

Scientists are trying to synthesize elements with more than 114 protons. State the expected atomic number of
(a) the newest inert gas.
(b) the new element with properties similar to those of the alkaline earth metals.
(c) the new element that will behave like the halogens.
(d) the new (nontransition) metal whose ion will have a +2 charge.
(e) the new element that will start period 8 .

Nicole Smina
Nicole Smina
Numerade Educator
02:48

Problem 84

Write the nuclear symbol for the element whose mass number is 234 and has $60 \%$ more neutrons than protons.

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
07:58

Problem 85

Mercury(II) oxide, a red powder, can be decomposed by heating to produce liquid mercury and oxygen gas. When a sample of this compound is decomposed, $3.87 \mathrm{~g}$ of oxygen and $48.43 \mathrm{~g}$ of mercury are produced. In a second experiment, $15.68 \mathrm{~g}$ of mercury is allowed to react with an excess of oxygen and $16.93 \mathrm{~g}$ of red mercury(II) oxide is produced. Show that these results are consistent with the law of constant composition.

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
02:46

Problem 86

Write the atomic symbol for the element whose ion has a -2 charge, has 20 more neutrons than electrons, and has a mass number of $126 .$

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
02:42

Problem 87

Consider the elements oxygen, fluorine, argon, sulfur, potassium, and strontium. From this group of elements, which ones fit the descriptions below?
(a) Two elements that are metals.
(b) Four elements that are nonmetals.
(c) Three elements that are solid at room temperature.
(d) An element that is found in nature as $\mathrm{X}_{8}$.
(e) One pair of elements that may form a molecular compound.
(f) One pair of elements that may form an ionic compound with formula AX.
(g) One pair of elements that may form an ionic compound with formula $\mathrm{AX}_{2}$
(h) One pair of elements that may form an ionic compound with formula $\mathrm{A}_{2} \mathrm{X}$
(i) An element that can form no compounds.
(j) Three elements that are gases at room temperature.

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
04:40

Problem 88

Three compounds containing only carbon and hydrogen are analyzed. The results for the analysis of the first two compounds are given below:
Which, if any, of the following results for the mass of hydrogen in compound
C follows the law of multiple proportions?
(a) $5.84 \mathrm{~g}$
(b) $3.47 \mathrm{~g}$
(c) $2.72 \mathrm{~g}$

Zaida Minjares
Zaida Minjares
Numerade Educator
04:14

Problem 89

Ethane and ethylene are two gases containing only hydrogen and carbon atoms. In a certain sample of ethane, $4.53 \mathrm{~g}$ of hydrogen is combined with $18.0 \mathrm{~g}$ of carbon. In a sample of ethylene, $7.25 \mathrm{~g}$ of hydrogen is combined with $43.20 \mathrm{~g}$ of carbon.
(a) Show how the data illustrate the law of multiple proportions.
(b) Suggest reasonable formulas for the two compounds.

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
03:12

Problem 90

Calculate the average density of a single Al-27 atom by assuming that it is a sphere with a radius of $0.143 \mathrm{nm}$. The masses of a proton, electron, and neutron are $1.6726 \times 10^{-24} \mathrm{~g}, 9.1094 \times 10^{-28} \mathrm{~g},$ and $1.6749 \times 10^{-24} \mathrm{~g},$ respec-
tively. The volume of a sphere is $4 \pi r^{3} / 3,$ where $r$ is its radius. Express the answer in grams per cubic centimeter. The density of aluminum is found experimentally to be $2.70 \mathrm{~g} / \mathrm{cm}^{3} .$ What does that suggest about the packing of aluminum atoms in the metal?

Crystal Wang
Crystal Wang
Numerade Educator
01:07

Problem 91

The mass of a beryllium atom is $1.4965 \times 10^{-23} \mathrm{~g}$. Using that fact and other information in this chapter, find the mass of a $\mathrm{Be}^{2+}$ ion.

Crystal Wang
Crystal Wang
Numerade Educator
11:44

Problem 92

Each time you inhale, you take in about $500 \mathrm{~mL}$ (two significant figures) of air, each milliliter of which contains $2.5 \times 10^{19}$ molecules. In delivering the Gettysburg Address, Abraham Lincoln is estimated to have inhaled about 200 times.
(a) How many molecules did Lincoln take in?
(b) In the entire atmosphere, there are about $1.1 \times 10^{44}$ molecules. What fraction of the molecules in the earth's atmosphere was inhaled by Lincoln at Gettysburg?
(c) In the next breath that you take, how many molecules were inhaled by Lincoln at Gettysburg?

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator