# CHEMISTRY: The Molecular Nature of Matter and Change 2016

## Educators

Problem 1

What is the key difference between an element and a compound

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Problem 2

List two differences between a compound and a mixture.

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Problem 3

List two differences between a compound and a mixture.
(a) Calcium chloride, used to melt ice on roads, consists of two elements, calcium and chlorine, in a fixed mass ratio.
(b) Sulfur consists of sulfur atoms combined into octatomic molecules.
(c) Baking powder, a leavening agent, contains 26$\%$ to 30$\%$ sodium hydrogen carbonate and 30$\%$ to 35$\%$ calcium dihydrogen phosphate by mass.
(d) Cytosine, a component of DNA, consists of H, C, N, and O atoms bonded in a specific arrangement.

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Problem 4

Classify each substance in Problem 2.3 as an element, compound, or mixture, and explain your answers.

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Problem 5

Explain the following statement: The smallest particles unique to an element may be atoms or molecules.

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Problem 6

Explain the following statement: The smallest particles unique to a compound cannot be atoms.

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Problem 7

Can the relative amounts of the components of a mixture vary? Can the relative amounts of the components of a compound vary? Explain.

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Problem 8

The tap water found in many areas of the United States leaves white deposits when it evaporates. Is this tap water a mixture or a compound? Explain.

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Problem 9

Each scene below represents a mixture. Describe each one in terms of the number(s) of elements and/or compounds present.

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Problem 10

Samples of illicit “street” drugs often contain an inactive component, such as ascorbic acid (vitamin C). After obtaining a sample of cocaine, government chemists calculate the mass of vitamin C per gram of drug sample, and use it to track the drug’s distribution. For example, if different samples of cocaine obtained on the streets of New York, Los Angeles, and Paris all contain 0.6384 g of vitamin C per gram of sample, they very likely come from a common source. Do these street samples consist of a compound, element, or mixture? Explain.

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Problem 11

Why was it necessary for separation techniques and methods of chemical analysis to be developed before the laws of definite composition and multiple proportions could be formulated?

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Problem 12

To which classes of matter—element, compound, and/or mixture—do the following apply: (a) law of mass conservation; (b) law of definite composition; (c) law of multiple proportions?

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Problem 13

In our modern view of matter and energy, is the law of mass conservation still relevant to chemical reactions? Explain.

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Problem 14

Identify the mass law that each of the following observations demonstrates, and explain your reasoning:
(a) A sample of potassium chloride from Chile chitains the same percent by mass of potassium as one from Poland.
(b) A flashbulb contains magnesium and oxygen before use and magnesium oxide afterward, but its mass does not change.
(c) Arsenic and oxygen form one compound that is 65.2 mass $\%$ arsenic and another that is 75.8 mass $\%$ arsenic.

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Problem 15

Which of the following scenes illustrate(s) the fact that compounds of chlorine (green) and oxygen (red) exhibit the law of multiple proportions? Name the compounds.

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Problem 16

(a) Does the percent by mass of each element in a compound depend on the amount of compound? Explain. (b) Does the mass of each element in a compound depend on the amount of compound? Explain

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Problem 17

Does the percent by mass of each element in a compound depend on the amount of that element used to make the compound? Explain

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Problem 18

State the mass law(s) demonstrated by the following experimental results, and explain your reasoning:
Experiment $1 :$ A student heats 1.00 $\mathrm{g}$ of a blue compound and obtains 0.64 $\mathrm{g}$ of a white compound and 0.36 $\mathrm{g}$ of a colorless gas. Experiment $2 : \mathrm{A}$ second student heats 3.25 $\mathrm{g}$ of the same blue compound and obtains 2.08 $\mathrm{g}$ of a white compound and 1.17 $\mathrm{g}$ of a colorless gas.

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Problem 19

State the mass law(s) demonstrated by the following experimental results, and explain your reasoning:
Experiment $1 :$ A student heats 1.27 g of copper and 3.50 g of iodine to produce 3.81 $\mathrm{g}$ of a white compound; 0.96 $\mathrm{g}$ of iodine remains. Experiment $2 : \mathrm{A}$ second student heats 2.55 $\mathrm{g}$ of copper and 3.50 $\mathrm{g}$ of iodine to form 5.25 $\mathrm{g}$ of a white compound; 0.80 $\mathrm{g}$ of copper remains.

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Problem 20

Fluorite, a mineral of calcium, is a compound of the metal with fluorine. Analysis shows that a 2.76-g sample of fluorite contains 1.42 g of calcium. Calculate the (a) mass of fluorine in the sample; (b) mass fractions of calcium and fluorine in fluorite; (c) mass percents of calcium and fluorine in fluorite

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Problem 21

Galena, a mineral of lead, is a compound of the metal with sulfur. Analysis shows that a 2.34-g sample of galena contains 2.03 g of lead. Calculate the (a) mass of sulfur in the sample; (b) mass fractions of lead and sulfur in galena; (c) mass percents of lead and sulfur in galena.

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Problem 22

Magnesium oxide (MgO) forms when the metal burns in air.
(a) If 1.25 g of MgO contains 0.754 g of Mg, what is the mass ratio of magnesium to magnesium oxide?
(b) How many grams of Mg are in 534 g of MgO?

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Problem 23

Zinc sulfide (ZnS) occurs in the zinc blende crystal structure.
(a) If 2.54 g of ZnS contains 1.70 g of Zn, what is the mass ratio of zinc to zinc sulfide?
(b) How many kilograms of Zn are in 3.82 kg of ZnS?

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Problem 24

A compound of copper and sulfur contains 88.39 g of metal and 44.61 g of nonmetal. How many grams of copper are in 5264 kg of compound? How many grams of sulfur?

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Problem 25

A compound of iodine and cesium contains 63.94 g of metal and 61.06 g of nonmetal. How many grams of cesium are in 38.77 g of compound? How many grams of iodine?

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Problem 26

Show, with calculations, how the following data illustrate the law of multiple proportions:
Compound $1 : 47.5$ mass $\%$ sulfur and 52.5 mass $\%$ chlorine
Compound $2 : 31.1$ mass $\%$ sulfur and 68.9 mass $\mathscr{C}$ chlorine

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Problem 27

Show, with calculations, how the following data illustrate the law of multiple proportions:
Compound $1 : 77.6$ mass $\%$ xenon and 22.4 mass $\%$ fluorine
Compound $2 : 63.3$ mass $\%$ xenon and 36.7 mass $\%$ fluorine

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Problem 28

Dolomite is a carbonate of magnesium and calcium. Analysis shows that 7.81 g of dolomite contains 1.70 g of Ca. Calculate the mass percent of Ca in dolomite. On the basis of the mass percent of Ca, and neglecting all other factors, which is the richer source of Ca, dolomite or fluorite (see Problem 2.20)?

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Problem 29

The mass percent of sulfur in a sample of coal is a key factor in the environmental impact of the coal because the sulfur combines with oxygen when the coal is burned and the oxide can then be incorporated into acid rain. Which of the following coals would have the smallest environmental impact?

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Problem 30

Which of Dalton’s postulates about atoms are inconsistent with later observations? Do these inconsistencies mean that Dalton was wrong? Is Dalton’s model still useful? Explain.

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Problem 31

Use Dalton’s theory to explain why potassium nitrate from India or Italy has the same mass percents of K, N, and O.

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Problem 32

Thomson was able to determine the mass/charge ratio of the electron but not its mass. How did Millikan’s experiment allow determination of the electron’s mass?

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Problem 33

The following charges on individual oil droplets were obtained during an experiment similar to Millikan's. Determine a charge for the electron (in $\mathrm{C},$ coulombs $),$ and explain your answer: $-3.204 \times 10^{-19} \mathrm{C} ;-4.806 \times 10^{-19} \mathrm{C} ;-8.010 \times 10^{-19} \mathrm{C}$
$-1.442 \times 10^{-18} \mathrm{C}$

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Problem 34

Describe Thomson’s model of the atom. How might it account for the production of cathode rays?

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Problem 35

When Rutherford’s coworkers bombarded gold foil with a particles, they obtained results that overturned the existing (Thomson) model of the atom. Explain.

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Problem 36

Define atomic number and mass number. Which can vary without changing the identity of the element?

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Problem 37

Choose the correct answer. The difference between the mass number of an isotope and its atomic number is (a) directly related to the identity of the element; (b) the number of electrons; (c) the number of neutrons; (d) the number of isotopes.

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Problem 38

Even though several elements have only one naturally occurring isotope and all atomic nuclei have whole numbers of protons and neutrons, no atomic mass is a whole number. Use the data from Table 2.2 to explain this fact.

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Problem 39

Argon has three naturally occurring isotopes, $^{36} \mathrm{Ar},^{38} \mathrm{Ar}$ , and 40 Ar. What is the mass number of each isotope? How many protons, neutrons, and electrons are present in each?

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Problem 40

Chlorine has two naturally occurring isotopes, $^{35} \mathrm{Cl}$ and $^{37} \mathrm{Cl}$ What is the mass number of each isotope? How many protons, neutrons, and electrons are present in each?

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Problem 41

Do both members of the following pairs have the same number of protons? Neutrons? Electrons?
$$\text{(a)}\frac{16}{8} \mathrm{O} \text { and } \stackrel{17}{8} \mathrm{O}$$
$$\text{(b)}\stackrel{14}{6} \mathrm{C} \text { and } \frac{15}{7} \mathrm{N}$$
$$\text{(c)}\frac{60}{27} \mathrm{Co} \text { and } \frac{60}{28} \mathrm{Ni}$$

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Problem 42

Do both members of the following pairs have the same number of protons? Neutrons? Electrons?
$$\text{(a)}_{1}^{3} \mathrm{H} \text { and }_{2}^{3} \mathrm{He}$$
$$\text{(b)}\stackrel{14}{6} \mathrm{C} \text { and } \stackrel{15}{7} \mathrm{N}$$
$$\text{(c)}\stackrel{19}{9} \mathrm{F} \text { and } \stackrel{18}{9} \mathrm{F}$$

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Problem 43

Write the $\frac{A}{z} X$ notation for each atomic depiction:

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Problem 44

Write the $_{Z}^{A} X$ notation for each atomic depiction:

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Problem 45

Draw atomic depictions similar to those in Problem 2.43 for
$$_{22}^{48} \mathrm{Ti} ;(\mathrm{b})_{34}^{79} \mathrm{Se} ;(\mathrm{c}) \stackrel{11}{5} \mathrm{B}$$

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Problem 46

Draw atomic depictions similar to those in Problem 2.43 for
$$\frac{207 \mathrm{Pb}}{82} \mathrm{Pb} ;(\mathrm{b})^{9} \mathrm{Be} ;(\mathrm{c})_{33}^{7} \mathrm{As}$$

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Problem 47

Gallium has two naturally occurring isotopes, 69 $\mathrm{Ga}$ (isotopic mass $=68.9256$ amu, abundance $=60.11 \%$ ) and $^{n}$ Ga (isotopic mass $=70.9247$ amu, abundance $=39.89 \%$ ). Calculate the atomic mass of gallium.

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Problem 48

Magnesium has three naturally occurring isotopes, 24 $\mathrm{Mg}$ (isotopic mass $=23.9850$ amu, abundance $=78.99 \% ), 25 \mathrm{Mg}$ (isotopic mass $=24.9858$ amu, abundance $=10.00 \%$ ), and $^{26} \mathrm{Mg}$

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Problem 49

Chlorine has two naturally occurring isotopes, $^{35} \mathrm{Cl}$ (isotopic mass $=34.9689$ amu) and $^{37} \mathrm{Cl}(\text { isotopic mass }=36.9659 \text { amu). If }$ chlorine has an atomic mass of 35.4527 $\mathrm{amu}$ , what is the percent abundance of each isotope?

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Problem 50

Copper has two naturally occurring isotopes, $^{63} \mathrm{Cu}$ (isotopicmass $=62.9296$ amu) and of Cu (isotopic mass $=64.9278$ amu). If copper has an atomic mass of 63.546 amu, what is the percent abundance of each isotope?

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Problem 51

How can iodine $(Z=53)$ have a higher atomic number yet a lower atomic mass than tellurium $(Z=52) ?$

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Problem 52

Correct each of the following statements:
(a) In the modern periodic table, the elements are arranged in order of increasing atomic mass.
(b) Elements in a period have similar chemical properties.
(c) Elements can be classified as either metalloids or nonmetals.

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Problem 53

What class of elements lies along the “staircase” line in the periodic table? How do the properties of these elements compare with those of metals and nonmetals?

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Problem 54

What are some characteristic properties of elements to the left of the elements along the "staircase"? To the right?

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Problem 55

The elements in Groups 1A(1) and 7A(17) are all quite reactive. What is a major difference between them?

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Problem 56

Give the name, atomic symbol, and group number of the element with each Z value, and classify it as a metal, metalloid, or nonmetal:
$$Z=32 \quad \text { (b) } Z=15 \quad(\mathrm{c}) Z=2 \quad \text { (d) } Z=3 \quad \text { (e) } Z=42$$

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Problem 57

Give the name, atomic symbol, and group number of the element with each Z value, and classify it as a metal, metalloid, or nonmetal:
$$Z=33 \quad \text { (b) } Z=20 \quad(\text { c) } Z=35 \quad \text { (d) } Z=19 \quad \text { (e) } Z=13$$

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Problem 58

Fill in the blanks:
(a) The symbol and atomic number of the heaviest alkaline earth metal are _____________ and _________
(b) The symbol and atomic number of the lightest metalloid in Group 4 $\mathrm{A}(14)$ are $\longrightarrow$ and _________
(c) Group 1 $\mathrm{B}(11)$ consists of the coinage metals. The symbol and atomic mass of the coinage metal whose atoms have the fewest electrons are $\frac{\text { and }}{\text { and }}$
(d) The symbol and atomic mass of the halogen in Period 4 are_____and_____

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Problem 59

Fill in the blanks:
(a) The symbol and atomic number of the heaviest nonradioactive noble gas are_______ and_______
(b) The symbol and group number of the Period 5 transition element whose atoms have the fewest protons are_______
(c) The elements in Group 6 $\mathrm{A}(16)$ are sometimes called the chalcogens. The symbol and atomic number of the first metallic chalcogen are_____
(d) The symbol and number of protons of the Period 4 alkali metal atom are $\longrightarrow$ and_____

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Problem 60

Describe the type and nature of the bonding that occurs between reactive metals and nonmetals.

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Problem 61

Describe the type and nature of the bonding that often occurs between two nonmetals.

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Problem 62

How can ionic compounds be neutral if they consist of positive and negative ions?

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Problem 63

Given that the ions in LiF and in MgO are of similar size, which compound has stronger ionic bonding? Use Coulomb’s law in your explanation.

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Problem 64

Are molecules present in a sample of $\mathrm{BaF}_{2} ?$ Explain.

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Problem 65

Are ions present in a sample of $\mathrm{P}_{4} \mathrm{O}_{6} ?$ Explain.

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Problem 66

The monatomic ions of Groups 1A(1) and 7A(17) are all singly charged. In what major way do they differ? Why?

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Problem 67

Describe the formation of solid magnesium chloride (MgCl_s) from large numbers of magnesium and chlorine atoms.

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Problem 68

Describe the formation of solid magnesium chloride $\left(\mathrm{MgCl}_{2}\right)$ large numbers of potassium and sulfur atoms.

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Problem 69

Does potassium nitrate $\left(\mathrm{KNO}_{3}\right)$ incorporate ionic bonding, Does potassium nitrate $\left(\mathrm{KNO}_{3}\right)$ incorporate ionic bonding,

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Problem 70

What monatomic ions would you expect potassium (Z 5 19) and bromine (Z 5 35) to form?

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Problem 71

What monatomic ions would you expect radium (Z 5 88) and selenium (Z 5 34) to form?

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Problem 72

For each ionic depiction, give the name of the parent atom, its mass number, and its group and period numbers:

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Problem 73

For each ionic depiction, give the name of the parent atom, its mass number, and its group and period numbers:

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Problem 74

An ionic compound forms when lithium $(Z=3)$ reacts with oxygen $(Z=8) .$ If a sample of the compound contains $8.4 \times 10^{21}$ lithium ions, how many oxide ions does it contain?

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Problem 75

An ionic compound forms when calcium $(Z=20)$ reacts with iodine $(Z=53) .$ If a sample of the compound contains $7.4 \times 10^{21}$ calcium ions, how many iodide ions does it contain?

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Problem 76

The radii of the sodium and potassium ions are 102 pm and 138 pm, respectively. Which compound has stronger ionic attractions, sodium chloride or potassium chloride?

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Problem 77

The radii of the lithium and magnesium ions are 76 pm and 72 pm, respectively. Which compound has stronger ionic attractions, lithium oxide or magnesium oxide?

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Problem 78

What information about the relative numbers of ions and the percent mass of elements is in the formula $\mathrm{MgF}_{2} ?$

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Problem 79

How is a structural formula similar to a molecular formula? How is it different?

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Problem 80

Consider a mixture of 10 billion $\mathrm{O}_{2}$ molecules and 10 billion $\mathrm{H}_{2}$ molecules. In what way is this mixture similar to a sample containing 10 billion hydrogen peroxide $\left(\mathrm{H}_{2} \mathrm{O}_{2}\right)$ molecules? In what way is it different?

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Problem 81

For what type(s) of compound do we use Roman numerals in the names?

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Problem 82

For what type(s) of compound do we use Greek numerical prefixes in the names?

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Problem 83

For what type of compound are we unable to write a molecular formula?

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Problem 84

Give the name and formula of the compound formed from the following elements: (a) sodium and nitrogen; (b) oxygen and strontium; (c) aluminum and chlorine.

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Problem 85

Give the name and formula of the compound formed from the following elements: (a) cesium and bromine; (b) sulfur and barium; (c) calcium and fluorine.

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Problem 86

Give the name and formula of the compound formed from the following elements
$$_{12} \mathrm{L} \text { and }_{9} \mathrm{M} \quad \text { (b) }_{30} \mathrm{L} \text { and }_{16} \mathrm{M} \quad \text { (c) }_{17} \mathrm{L} \text { and }_{38} \mathrm{M}$$

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Problem 87

Give the name and formula of the compound formed from the following elements:
$$\begin{array}{ll}{\text { (a) }_{37} \mathrm{Q} \text { and }_{35} \mathrm{R}} & {\text { (b) }_{8} \mathrm{Q} \text { and }_{13} \mathrm{R}} & {\text { (c) }_{20} \mathrm{Q} \text { and }_{53} \mathrm{R}}\end{array}$$

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Problem 88

Give the systematic names for the formulas or the formulas for the names: (a) tin(IV) chloride; (b) FeBr; bromide; (d) $\mathrm{Mn}_{2} \mathrm{O}_{3}$

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Problem 89

Give the systematic names for the formulas or the formulas for the names: (a) $\mathrm{Na}_{2} \mathrm{HPO}_{4} ;(\mathrm{b})$ potassium carbonate dihydrate; (c) $\mathrm{NaNO}_{2} ;(\mathrm{d})$ ammonium perchlorate.

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Problem 90

Give the systematic names for the formulas or give the formulas for the names: (a) CoO; (b) mercury(I) chloride; (c) $\mathrm{Pb}\left(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)_{2} \cdot 3 \mathrm{H}_{2} \mathrm{O} ;(\mathrm{d})$ chromic oxide.

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Problem 91

Give the systematic names for the formulas or the formulas for the names: (a) $\operatorname{Sn}\left(\mathrm{SO}_{3}\right)_{2} ;(\mathrm{b})$ potassium dichromate; $(\mathrm{c}) \mathrm{FeCO}_{3}$ (d) copper(II) nitrate.

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Problem 92

Correct each of the following formulas:
(a) Barium oxide is $\mathrm{BaO}_{2}$
(b) Iron(II) nitrate is $\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3}$
(c) Magnesium sulfide is MnSO $_{3}$

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Problem 93

Correct each of the following names:
(a) Cul is cobalt (II) iodide
(b) $\mathrm{Fe}\left(\mathrm{HSO}_{4}\right)_{3}$ is iron(II) sulfate
(c) $\mathrm{MgCr}_{2} \mathrm{O}_{7}$ is magnesium dichromium heptaoxide

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Problem 94

Give the name and formula for the acid derived from each of the following anions:
(a) hydrogen carbonate
(b) $\mathrm{IO}_{4}^{-}$
(c) cyanide
(d) HS -

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Problem 95

Give the name and formula for the acid derived from each of the following anions:
(a) perchlorate
(b) $\mathrm{NO}_{3}^{-}$
(c) bromite
(d) $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}$

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Problem 96

Many chemical names are similar at first glance. Give the formulas of the species in each set:
(a) Ammonium ion and ammonia
(b) Magnesium sulfide, magnesium sulfite, and magnesium sulfate
(c) Hydrochloric acid, chloric acid, and chlorous acid
(d) Cuprous bromide and cupric bromide

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Problem 97

Give the formulas of the compounds in each set:
(b) Lithium nitride, lithium nitrite, and lithium nitrate
(c) Strontium hydride and strontium hydroxide
(d) Magnesium oxide and manganese(\Pi) oxide

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Problem 98

Give the name and formula of the compound whose molecules consist of two sulfur atoms and four fluorine atoms

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Problem 99

Give the name and formula of the compound whose molecules consist of two chlorine atoms and one oxygen atom

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Problem 100

Correct the name to match the formula of the following compounds: (a) calcium(II) dichloride, $\mathrm{CaCl}_{2} ;$ (b) copper(\Pii) oxide, $\mathrm{Cu}_{2} \mathrm{O} ;(\mathrm{c})$ stannous tetrafluoride, $\mathrm{SnF}_{4} ;$ (d) hydrogen chloride acid, HCl.

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Problem 101

Correct the formula to match the name of the following compounds: (a) iron(II) oxide, $\mathrm{Fe}_{3} \mathrm{O}_{4} ;$ (b) chloric acid, $\mathrm{HCl} ;$ (c) mercuric oxide, $\mathrm{Hg}_{2} \mathrm{O} ;(\mathrm{d})$ potassium iodide, $\mathrm{P}_{2} \mathrm{I}_{3}$ .

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Problem 102

Write the formula of each compound, and determine itsmolecular (formula) mass: (a) ammonium sulfate; (b) sodium dihydrogen phosphate; (c) potassium bicarbonate

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Problem 103

Write the formula of each compound, and determine its molecular (formula) mass: (a) sodium dichromate; (b) ammonium perchlorate; (c) magnesium nitrite trihydrate.

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Problem 104

Calculate the molecular (formula) mass of each compound: (a) dinitrogen pentoxide; (b) lead(II) nitrate; (c) calcium peroxide.

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Problem 105

Calculate the molecular (formula) mass of each compound: (a) iron(II) acetate tetrahydrate; (b) sulfur tetrachloride; (c) potassium permanganate

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Problem 106

Give the number of atoms of the specified element in a formula unit of each of the following compounds, and calculate the molecular (formula) mass:
(a) Oxygen in aluminum sulfate, Al_{?} ( \mathrm { SO } _ { 4 } ) _ { 3 }
(b) Hydrogen in ammonium hydrogen phosphate, (NH $_{4} )_{2} \mathrm{HPO}_{4}$
(c) Oxygen in the mineral azurite, $\mathrm{Cu}_{3}(\mathrm{OH})_{2}\left(\mathrm{CO}_{3}\right)_{2}$

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Problem 107

Give the number of atoms of the specified element in a formula unit of each of the following compounds, and calculate the molecular (formula) mass:
(a) Hydrogen in ammonium benzoate, $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COONH}_{4}$
(b) Nitrogen in hydrazinium sulfate, $\mathrm{N}_{2} \mathrm{H}_{6} \mathrm{SO}_{4}$
(c) Oxygen in the mineral leadhillite, $\mathrm{Pb}_{4} \mathrm{SO}_{4}\left(\mathrm{CO}_{3}\right)_{2}(\mathrm{OH})_{2}$

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Problem 108

Give the formula, name, and molecular mass of the following molecules:

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Problem 109

Give the formula, name, and molecular mass of the following molecules:

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Problem 110

Before the use of systematic names, many compounds had common names. Give the systematic name for each of the following:
(a) Blue vitriol, CuSO $_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O}$
(b) Slaked lime, $\mathrm{Ca}(\mathrm{OH})_{2}$
(c) Oil of vitriol, $\mathrm{H}_{2} \mathrm{SO}_{4}$
(d) Washing soda, $\mathrm{Na}_{2} \mathrm{CO}_{3}$
(e) Muriatic acid, HCl
(f) Epsom salt, MgSO_ $\cdot 7 \mathrm{H}_{2} \mathrm{O}$
(g) Chalk, CaCO_ $_{3}$
(h) Dry ice, $\mathrm{CO}_{2}$
(i) Baking soda, NaHCO_{3}
(j) Lye, NaOH

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Problem 111

Each circle contains a representation of a binary compound. Determine its name, formula, and molecular (formula) mass.

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Problem 112

In what main way is separating the components of a mixture different from separating the components of a compound?

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Problem 113

What is the difference between a homogeneous and a heterogeneous mixture?

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Problem 114

Is a solution a homogeneous or a heterogeneous mixture? Give an example of an aqueous solution.

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Problem 115

Classify each of the following as a compound, a homogeneous mixture, or a heterogeneous mixture: (a) distilled water; (b) gasoline; (c) beach sand; (d) wine; (e) air.

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Problem 116

Classify each of the following as a compound, a homogeneous mixture, or a heterogeneous mixture: (a) orange juice; (b) vegetable soup; (c) cement; (d) calcium sulfate; (e) tea.

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Problem 117

Which separation method is operating in each of the following procedures?
(a) Pouring a mixture of cooked pasta and boiling water into a colander
(b) Removing colored impurities from raw sugar to make refined sugar

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Problem 118

A quality-control laboratory analyzes a product mixture using gas-liquid chromatography. The separation of components is more than adequate, but the process takes too long. Suggest two ways, other than changing the stationary phase, to shorten the analysis time

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Problem 119

Helium is the lightest noble gas and the second most abundant element (after hydrogen) in the universe.
(a) The radius of a helium atom is $3.1 \times 10^{-11} \mathrm{m} ;$ the radius of its nucleus is $2.5 \times 10^{-15} \mathrm{m} .$ What fraction of the spherical atomic volume is occupied by the nucleus $\left(V \text { of a sphere }=\frac{4}{3} \pi r^{3}\right) ?$
(b) The mass of a helium- 4 atom is $6.64648 \times 10^{-24} \mathrm{g},$ and each of its two electrons has a mass of $9.10939 \times 10^{-28} \mathrm{g} .$ What fraction of this atom's mass is contributed by its nucleus?

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Problem 120

From the following ions (with their radii in pm), choose the pair that forms the strongest ionic bond and the pair that forms the weakest:
$$\begin{array}{llllll}{\text { Ion: }} & {\mathrm{Mg}^{2+}} & {\mathrm{Rb}^{+}} & {\mathrm{Rb}^{+}} & {\mathrm{Ba}^{2+}} & {\mathrm{Cl}^{2+}} & {\mathrm{Cl}^{-}} & {\mathrm{O}^{2-}} & {\mathrm{I}^{-}} \\ {\mathrm{Radius} :} & {72} & {138} & {152} & {135} & {181} & {140} & {220}\end{array}$$

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Problem 121

Give the molecular mass of each compound depicted below, and provide a correct name for any that are named incorrectly

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Problem 122

Polyatomic ions are named by patterns that apply to elements in a given group. Using the periodic table and Table $2.5,$ give the name of each of the following: (a) $\mathrm{SeO}_{4}^{2-} ;(\mathrm{b}) \mathrm{AsO}_{4}^{3-} ;$

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Problem 123

Ammonium dihydrogen phosphate, formed from the reaction of phosphoric acid with ammonia, is used as a crop fertilizer as well as a component of some fire extinguishers. (a) What are the mass percentages of N and P in the compound? (b) How much ammonia is incorporated into 100. g of the compound?

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Problem 124

Nitrogen forms more oxides than any other element. The percents by mass of $\mathrm{N}$ in three different nitrogen oxides are (1) $46.69 \%,$ (II) $36.85 \%,$ and (III) 25.94$\% .$ For each compound,
determine (a) the simplest whole-number ratio of $\mathrm{N}$ to $\mathrm{O}$ and (b) the number of grams of oxygen per 1.00 $\mathrm{g}$ of nitrogen.

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Problem 125

The number of atoms in 1 $\mathrm{dm}^{3}$ of aluminum is nearly the same as the number of atoms in 1 $\mathrm{dm}^{3}$ of lead, but the densities of these metals are very different (see Table 1.5$) .$ Explain.

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Problem 126

You are working in the laboratory preparing sodium chloride. Consider the following results for three preparations of the compound:
$$\begin{array}{l}{\text { Case } 1 : 39.34 \mathrm{g} \mathrm{Na}+60.66 \mathrm{g} \mathrm{Cl}_{2} \longrightarrow 100.00 \mathrm{g} \mathrm{NaCl}} \\ {\text { Case } 2 : 39.34 \mathrm{g} \mathrm{Na}+70.00 \mathrm{g} \mathrm{Cl}_{2}} & {\longrightarrow} \\ {100.00 \mathrm{g} \mathrm{NaCl}+9.34 \mathrm{gCl}_{2}}\end{array}$$
$$3 : 50.00 \mathrm{g} \mathrm{Na}+50.00 \mathrm{g} \mathrm{Cl}_{2} \longrightarrow_{82.43 \mathrm{g} \mathrm{NaCl}+17.57 \mathrm{g} \mathrm{Na}}$$

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Problem 127

Scenes A–I depict various types of matter on the atomic scale. Choose the correct scene(s) for each of the following:
(a) A mixture that fills its container
(b) A substance that cannot be broken down into simpler ones
(c) An element with a very high resistance to flow
(d) A homogeneous mixture
(e) An element that conforms to the walls of its container and
displays an upper surface
(f) A gas consisting of diatomic particles
(g) A gas that can be broken down into simpler substances
(h) A substance with a 2/1 ratio of its component atoms
(i) Matter that can be separated into its component substances by
physical means
(j) A heterogeneous mixture
(k) Matter that obeys the law of definite composition

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Problem 128

The seven most abundant ions in seawater make up more than 99% by mass of the dissolved compounds. Here are their abundances in units of mg ion/kg seawater: chloride 18,980; sodium 10,560; sulfate 2650; magnesium 1270; calcium 400; potassium 380; hydrogen carbonate 140.
(a) What is the mass % of each ion in seawater?
(b) What percent of the total mass of ions is sodium ion?
(c) How does the total mass % of alkaline earth metal ions compare with the total mass % of alkali metal ions?
(d) Which make up the larger mass fraction of dissolved components, anions or cations?

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Problem 129

The scenes on the next page represent a mixture of two monatomic gases undergoing a reaction when heated. Which mass law(s) is (are) illustrated by this change?

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Problem 130

When barium (Ba) reacts with sulfur (S) to form barium sulfide (BaS), each Ba atom reacts with an $\mathrm{S}$ atom. If 2.50 $\mathrm{cm}^{3}$ of Ba reacts with 1.75 $\mathrm{cm}^{3}$ of $\mathrm{S},$ are there enough Ba atoms to react with the S atoms $\left(d \text { of } \mathrm{Ba}=3.51 \mathrm{g} / \mathrm{cm}^{3} ; d \text { of } \mathrm{S}=2.07 \mathrm{g} / \mathrm{cm}^{3}\right) ?$

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Problem 131

Succinic acid (below) is an important metabolite in biological energy production. Give the molecular formula, molecular mass, and the mass percent of each element in succinic acid.

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Problem 132

Fluoride ion is poisonous in relatively low amounts: 0.2 $\mathrm{g}$ of $\mathrm{F}^{-}$ per 70 $\mathrm{kg}$ of body weight can cause death. Nevertheless, in order to prevent tooth decay, $\mathrm{F}^{-}$ ions are added to drinking water at a concentration of 1 $\mathrm{mg}$ of $\mathrm{F}^{-}$ ion per $\mathrm{L}$ of water. How many liters of fluoridated drinking water would a $70-\mathrm{kg}$ per-son have to consume in one day to reach this toxic level? How many kilograms of sodium fluoride would be needed to treat a $8.50 \times 10^{7}$ -gal reservoir?

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Problem 133

Antimony has many uses, for example, in infrared devices and as part of an alloy in lead storage batteries. The element has two naturally occurring isotopes, one with mass 120.904 amu, the other with mass 122.904 amu. (a) Write the $\frac{A}{2} \mathrm{X}$ notation for each isotope. (b) Use the atomic mass of antimony from the periodic table to calculate the natural abundance of each isotope.

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Problem 134

Dinitrogen monoxide $\left(\mathrm{N}_{2} \mathrm{O} ; \text { nitrous oxide ) is a greenhouse }\right.$
gas that enters the atmosphere principally from natural fertilizer breakdown. Some studies have shown that the isotope ratios of 15 $\mathrm{N}$ to 14 $\mathrm{N}$ and of 18 $\mathrm{O}$ to 16 $\mathrm{O}$ in $\mathrm{N}_{2} \mathrm{O}$ depend on the source, which can thus be determined by measuring the relative abundance of molecular masses in a sample of $\mathrm{N}_{2} \mathrm{O}$ .
(a) What different molecular masses are possible for $\mathrm{N}_{2} \mathrm{O}$ ?
(b) The percent abundance of 14 $\mathrm{N}$ is $99.6 \%,$ and that of 16 $\mathrm{O}$ is
99.8$\%$ . Which molecular mass of $\mathrm{N}_{2} \mathrm{O}$ is least common, and which is most common?

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Problem 135

Use the box color(s) in the periodic table below to identify the element(s) described by each of the following:
(a) Four elements that are nonmetals
(b) Two elements that are metals
(c) Three elements that are gases at room temperature
(d) Three elements that are solid at room temperature
(e) One pair of elements likely to form a covalent compound
(f) Another pair of elements likely to form a covalent compound
(g) One pair of elements likely to form an ionic compound with formula MX
(h) Another pair of elements likely to form an ionic compound with formula MX
(i) Two elements likely to form an ionic compound with formula M2X
(j) Two elements likely to form an ionic compound with formula MX2
(k) An element that forms no compounds
(l) A pair of elements whose compounds exhibit the law of multiple proportions

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Problem 136

The two isotopes of potassium with significant abundance in nature are $^{39} \mathrm{K}$ (isotopic mass 38.9637 amu, 93.258$\% )$ and $^{41} \mathrm{K}$ (isotopic mass $40.9618 \mathrm{amu}, 6.730 \%$ ). Fluorine has only one naturally occurring isotope, 19 $\mathrm{F}$ (isotopic mass 18.9984 amu). Calculate the formula mass of potassium fluoride.

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Problem 137

Boron trifluoride is used as a catalyst in the synthesis of organic compounds. When this compound is analyzed by mass spectrometry ( see Tools of the Laboratory, p. 57 ), several different $1+$ ions form, including ions representing the whole molecule as well as molecular fragments formed by the loss of one, two, and three $\mathrm{F}$ atoms. Given that boron has two naturally occurring iso-
topes, 10 $\mathrm{B}$ and 11 $\mathrm{B}$ , and fluorine has one, 19 $\mathrm{F}$ , calculate the masses of all possible $1+$ ions.

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Problem 138

Nitrogen monoxide (NO) is a bioactive molecule in blood. Low NO concentrations cause respiratory distress and the formation of blood clots. Doctors prescribe nitroglycerin, $\mathrm{C}_{3} \mathrm{H}_{5} \mathrm{N}_{3} \mathrm{O}_{9}$ each compound releases one molecule of NO per atom of N it contains, calculate the mass percent of NO in each.

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Problem 139

TNT (trinitrotoluene; below) is used as an explosive in construction. Calculate the mass of each element in 1.00 lb of TNT.

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Problem 140

Nuclei differ in their stability, and some are so unstable that they undergo radioactive decay. The ratio of the number of neutrons to number of protons $(N / Z)$ in a nucleus correlates with its stability. Calculate the $N / Z$ ratio for $(a)^{144} \mathrm{Sm} ;(\mathrm{b})^{56} \mathrm{Fe}$ (c) 20 Ne; (d) 107 $\mathrm{Ag}$ . (e) The radioactive isotope 238 $\mathrm{U}$ decays in a series of nuclear reactions that includes another uranium isotope, 234 $\mathrm{U}$ , and three lead isotopes, $214 \mathrm{Pb}, 210 \mathrm{Pb}$ , and 206 $\mathrm{Pb}$ . How many neutrons, protons, and electrons are in each of these five isotopes?

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Problem 141

The anticancer drug Platinol (cisplatin), $\operatorname{Pt}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}$ reacts with the cancer cell's DNA and interferes with its growth. (a) What is the mass $\%$ of platinum (Pt) in Platinol? (b) If Pt costs $\$ 51 / \mathrm{g},$how many grams of Platinol can be made for$\$1.00$ million (assume that the cost of Pt determines the cost of the drug)?

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Problem 142

In the periodic table below, give the name, symbol, atomic number, atomic mass, period number, and group number of (a) the building-block elements (red), which occur in nearly every biological molecule, and (b) the macronutrients (green), which are either essential ions in cell fluids or are part of many
biomolecules.

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Problem 143

The block diagram below classifies the components of matter on the macroscopic scale. Identify blocks (a)–(d).

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Problem 144

Which of the steps in the following process involve(s) a physical change and which involve(s) a chemical change?

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