Determine the number of protons and the number of neutrons in each isotope. a. 40 19K b

Two samples of carbon tetrachloride were decomposed into their constituent elements. One sample produced 38.9 g of carbon and 448 g of chlorine, and the other sample produced 14.8 g of carbon and 134 g of chlorine. Are these results consistent with the law of definite proportions? Show why or why not.

Two samples of sodium chloride were decomposed into their constituent elements. One sample produced 6.98 g of sodium and 10.7 g of chlorine, and the other sample produced 11.2 g of sodium and 17.3 g of chlorine. Are these results consistent with the law of definite proportions? Explain your answer.

The mass ratio of sodium to fluorine in sodium fluoride is 1.21:1. A sample of sodium fluoride produces 28.8 g of sodium upon decomposition. How much fluorine (in grams) is formed?

Upon decomposition, one sample of magnesium fluoride produced 1.65 kg of magnesium and 2.57 kg of fluorine. A second sample produced 1.32 kg of magnesium. How much fluorine (in grams) did the second sample produce?

Palladium forms three different compounds with sulfur. The mass of sulfur per gram of palladium in each compound is listed below. Show that these masses are consistent with the law of multiple proportions.

Two different compounds containing osmium and oxygen have the following masses of oxygen per gram of osmium: 0.168 and 0.3369 g. Show that these amounts are consistent with the law of multiple proportions.

Sulfur and oxygen form both sulfur dioxide and sulfur trioxide. When samples of these were decomposed the sulfur dioxide produced 3.49 g oxygen and 3.50 g sulfur, while the sulfur trioxide produced 6.75 g oxygen and 4.50 g sulfur. Calculate the mass of oxygen per gram of sulfur for each sample and show that these results are consistent with the law of multiple proportions.

Sulfur and fluorine form several different compounds including sulfur hexafluoride and sulfur tetrafluoride. Decomposition of a sample of sulfur hexafluoride produces 4.45 g of fluorine and 1.25 g of sulfur, while decomposition of a sample of sulfur tetrafluoride produces 4.43 g of fluorine and 1.87 g of sulfur. Calculate the mass of fluorine per gram of sulfur for each sample and show that these results are consistent with the law of multiple proportions

Which statements are consistent with Dalton’s atomic theory as it was originally stated? Why? a. Sulfur and oxygen atoms have the same mass. b. All cobalt atoms are identical. c. Potassium and chlorine atoms combine in a 1:1 ratio to form potassium chloride. d. Lead atoms can be converted into gold.

Which statements are consistent with Rutherford’s nuclear theory as it was originally stated? Why? a. The volume of an atom is mostly empty space. b. The nucleus of an atom is small compared to the size of the atom. c. Neutral lithium atoms contain more neutrons than protons. d. Neutral lithium atoms contain more protons than electrons.

Which statements are inconsistent with Rutherford’s nuclear theory as it was originally stated? Why? a. Since electrons are smaller than protons, and since a hydrogen atom contains only 1 proton and 1 electron, it must follow that the volume of a hydrogen atom is mostly due to the proton. b. A nitrogen atom has 7 protons in its nucleus and 7 electrons outside of its nucleus. c. A phosphorus atom has 15 protons in its nucleus and 150 electrons outside of its nucleus. d. The majority of the mass of a fluorine atom is due to its 9 electrons.

Which statements are inconsistent with Dalton’s atomic theory as it was originally stated? Why? a. All carbon atoms are identical. b. An oxygen atom combines with 1.5 hydrogen atoms to form a water molecule. c. Two oxygen atoms combine with a carbon atom to form a carbon dioxide molecule. d. The formation of a compound often involves the destruction of one or more atoms.

Imagine a unit of charge called the zorg. A chemist performs the oil drop experiment and measures the charge of each drop in zorgs. Based on the results shown here, what is the charge of the electron in zorgs (z)? How many electrons are in each drop?

A chemist in an imaginary universe, where electrons have a different charge than they do in our universe, performs the Millikan oil drop experiment to measure the electron’s charge. The charges of several drops are recorded here. What is the charge of the electron in this imaginary universe?

On a dry day, your body can accumulate static charge from walking across a carpet or from brushing your hair. If your body develops a charge of - 15 C ( microcoulombs), how many excess electrons has it acquired? What is their collective mass?

How many electrons are necessary to produce a charge of -1.0 C? What is the mass of this many electrons?

Which statements about subatomic particles are true? a. If an atom has an equal number of protons and electrons, it will be charge-neutral. b. Electrons are attracted to protons. c. Electrons are much lighter than neutrons. d. Protons have twice the mass of neutrons.

Which statements about subatomic particles are false? a. Protons and electrons have charges of the same magnitude but opposite signs. b. Protons have about the same mass as neutrons. c. Some atoms don’t have any protons. d. Protons and neutrons have charges of the same magnitude but opposite signs.

How many electrons would it take to equal the mass of a proton?

A helium nucleus has two protons and two neutrons. How many electrons would it take to equal the mass of a helium nucleus?

Write isotopic symbols in the form X- A (e.g., C-13) for each isotope. a. the silver isotope with 60 neutrons b. the silver isotope with 62 neutrons c. the uranium isotope with 146 neutrons d. the hydrogen isotope with 1 neutron

Write isotopic symbols in the form for each isotope. a. the copper isotope with 34 neutrons b. the copper isotope with 36 neutrons c. the potassium isotope with 21 neutrons d. the argon isotope with 22 neutrons

Determine the number of protons and the number of neutrons in each isotope. a. b. c. d.

Determine the number of protons and the number of neutrons in each isotope. a. b. c. d.

The amount of carbon-14 in ancient artifacts and fossils is often used to establish their age. Determine the number of protons and the number of neutrons in a carbon-14 isotope and write its symbol in the form .

Uranium-235 is used in nuclear fission. Determine the number of protons and the number of neutrons in uranium-235 and write its symbol in the form .

Determine the number of protons and the number of electrons in each ion. a. Ni2+ b. S2- c. Br - d. Cr3+

Determine the number of protons and the number of electrons in each ion. a. Al3+ b. Se2- c. Ga3+ d. Sr2+

Predict the charge of the ion formed by each element. a. O b. K c. Al d. Rb

Predict the charge of the ion formed by each element. a. Mg b. N c. F d. Na

Fill in the blanks to complete the table.

Fill in the blanks to complete the table.

Write the name of each element and classify it as a metal, nonmetal, or metalloid. a. K b. Ba c. I d. O e. Sb

Write the symbol for each element and classify it as a metal, nonmetal, or metalloid. a. gold b. fluorine c. sodium d. tin e. argon

Determine whether or not each element is a main-group element. a. tellurium b. potassium c. vanadium d. manganese

Determine whether or not each element is a transition element. a. Cr b. Br c. Mo d. Cs

The atomic mass of copper is 63.546 amu. Do any copper isotopes have a mass of 63.546 amu? Explain.

The atomic mass of copper is 63.546 amu. Do any copper isotopes have a mass of 63.546 amu? Explain.

An element has four naturally occurring isotopes with the masses and natural abundances given here. Find the atomic mass of the element and identify it.

Problem 78 Naming Inorganic Compounds; Some Simple Organic Compounds (Sections) The oxides of nitrogen are very important components in urban air pollution. Name each of the following compounds: (a) N? O, (b) NO, (c) NO? , (d) N? O? , (e) N? O? . 2? 2? 2? 5? 2? 4?

Bromine has two naturally occurring isotopes (Br-79 and Br-81) and has an atomic mass of 79.904 amu. The mass of Br-81 is 80.9163 amu, and its natural abundance is 49.31%. Calculate the mass and natural abundance of Br-79.

Problem 79 Naming Inorganic Compounds; Some Simple Organic Compounds (Sections) Write the chemical formula for each substance mentioned in the following word descriptions (use the front inside cover to find the symbols for the elements you do not know), (a) Zinc carbonate can be heated to form zinc oxide and carbon dioxide. (b) On treatment with hydrofluoric acid, silicon dioxide forms silicon tetrafluoride and water. (c) Sulfur dioxide reacts with water to form sulfurous acid. (d) The substance phosphorus trihydride, commonly called phosphine, is a toxic gas. (e) Perchloric acid reacts with cadmium to form cadmium(ll) perchlorate. (f) Vanadium(lll) bromide is a colored solid.

Use the mass spectrum of rubidium to determine the atomic mass of rubidium.

How many moles of aluminum do 3.7 x 1024 aluminum atoms represent?

Problem 83 Naming Inorganic Compounds; Some Simple Organic Compounds (Sections) (a) What is a functional group? (b) What functional group characterizes an alcohol? (c) Write a structural formula for 1-pentanol, the alcohol derived from pentane by making a substitution on one of the carbon atoms.

What is the mass, in grams, of each elemental sample? a. 2.3 x 10-3 mol Sb b. 0.0355 mol Ba c. 43.9 mol Xe d. 1.3 mol W

Problem 89 A cube of gold that is 1.00 cm on a side has a mass of 19.3 g. A single gold atom has a mass of 197.0 amu. (a) How many gold atoms are in the cube? (b) From the information given, estimate the diameter in Å o ? f a single gold atom. (c) What assumptions did you make in arriving at your answer for part (b)?

Problem 90 The diameter of a rubidium atom is 4.95 ???. We will consider two different ways of placing the atoms on a surface. In arrangement A, all the atoms are lined up with one another to form a square grid. Arrangement B is called a close-packed arrangement because the atoms sit in the 'depressions' formed by the previous row of atoms: (a) Using arrangement A, how many Rb atoms could be placed on a square surface that is 1.0 cm on a side? (b) How many Rb atoms could be placed on a square surface that is 1.0 cm on a side, using arrangement B? (c) By what factor has the number of atoms on the surface increased in going to arrangement B from arrangement A? If extended to three dimensions, which arrangement would lead to a greater density for Rb metal?

Problem 91 (a) Assuming the dimensions of the nucleus and atom shown in Figure 2.10, what fraction of the volume of the atom is taken up by the nucleus? -15? b) Using the mass of the proton from Table and assuming its diameter is 1.0 × 10? m, calculate the density of a proton in g/cm3.

Problem 92 Identify the element represented by each of the following symbols and give the number of protons and neutrons in each: (a) , (b) , (c) , (d) .

Problem 94 The element oxygen has three naturally occurring isotopes, with 8, 9, and 10 neutrons in the nucleus, respectively, (a) Write the full chemical symbols for these three isotopes, (b) Describe the similarities and differences between the three kinds of atoms of oxygen.

Problem 93 6? The nucleus of ? Li is a powerful absorber of neutrons. It exists in the naturally occurring metal to the extent of 7.5%. In the era of nuclear deterrence, large quantities of lithium were processed to remove ? Li for use in hydrogen bomb production. The lithium metal remaining after removal of ? Li was sold on the market, 6? 7? (a) What are the compositions of the nuclei of ? Li and ? Li? 6? 7? (b)The atomic masses of ? Li and ? Li are 6.015122 and 7.016004 amu, respectively. A sample of lithium depleted in the lighter isotope was found on analysis to contain 1.442% ? Li. What is the average atomic weight of this sample of the metal?

Problem 95 The element lead (Pb) consists of four naturally occurring isotopes with atomic masses 203.97302, 205.97444, 206.97587, and 207.97663 amu. The relative abundances of these four isotopes are 1.4, 24.1, 22.1, and 52.4% respectively. From these data, calculate the atomic weight of lead.

Problem 96 Gallium (Ga) consists of two naturally occurring isotopes with masses of 68.926 and 70.925 amu. (a) How many protons and neutrons are in the nucleus of each isotope? Write the complete atomic symbol for each, showing the atomic number and mass number, (b) The average atomic mass of Ga is 69.72 amu. Calculate the abundance of each isotope.

Problem 97 Using a suitable reference such as the CRC Handbook of Chemistry and Physics or http://www.webelements.com, look up the following information for nickel: (a) the number of known isotopes, (b) the atomic masses (in amu), (c) the natural abundances of the five most abundant isotopes.

Problem 98 There are two different isotopes of bromine atoms. Under normal conditions, elemental bromine consists of Br? molec2?es, and the mass of a Br? molecule is th2?sum of the masses of the two atoms in the molecule. The mass spectrum of Br? consists of thre2?peaks: (a) What is the origin of each peak (of what isotopes does each consist)? (b) What is the mass of each isotope? (c) Determine the average molecular mass of a Br? molecule, 2? (d) Determine the average atomic mass of a bromine atom, (e) Calculate the abundances of the two isotopes.

Problem 100 From the following list of elements—Ar, H, Ga, Al, Ca, Br, Ge, K, O—pick the one that best fits each description. Use each element only once: (a) an alkali metal. (b) an alkaline earth metal. (c) a noble gas. (d) a halogen. (e) a metalloid. (f) a nonmetal listed in group 1A. (g) a metal that forms a 3+ ion. (h) a nonmetal that forms a 2-ion. (i) an element that resembles aluminum.

Problem 99 It is common in mass spectrometry to assume that the mass of a cation is the same as that of its parent atom. (a) Using data in Table, determine the number of significant figures that must be reported 1? 1? +? before the difference in masses of ? H and ? H? is significant. Table Comparison of the Proton, Neutron, and Electron 1? (b) What percentage of the mass of an ? H atom does the electron represent?

Problem 101 The first atoms of seaborgium (Sg) were identified in 1974. The longest-lived isotope of Sg has a mass number of 266. 266? (a) How many protons, electrons, and neutrons are in an ? Sg atom? (b) Atoms of Sg are very unstable, and it is therefore difficult to study this element's properties. Based on the position of Sg in the periodic table, what element should it most closely resemble in its chemical properties?

Problem 102AE The explosion of an atomic bomb releases many radioactive isotopes, including strontium-90. Considering the location of strontium in the periodic table, suggest a reason for the fact that this isotope is particularly dangerous for human health.

Problem 104 From the molecular structures shown here, identify the one that corresponds to each of the following species: (a) chlorine gas, (b) propane, (c) nitrate ion, (d) sulfur trioxide, (e) methyl chloride, CH3CI.

Problem 104AE Name each of the following oxides. Assuming that the compounds are ionic, what charge is associated with the metallic element in each case? (a) NiO, (b) MnO2, (c) Cr2O3, (d) MoO3.,

Problem 105 Fill in the blanks in the following table: Cation Anion Formula Name Lithium oxide 2+ 3- Fe? PO?4? Al? (SO? )? 2? 4? 3 Copper(II) nitrate Cr?3+ I? MnClO? 2 Ammonium carbonate Zinc perchlorate

Problem 106 Cyclopropane is an interesting hydrocarbon. Instead of having three carbons in a row, the three carbons form a ring, as shown in this perspective Figure 2 (see Figure 1.1 and Figure 1.2 for a prior example of this kind of drawing): Figure 1.1 Figure 1.2 Figure 2 Cyclopropane was at one time used as an anesthetic, but its use was discontinued, in part because it is highly inflammable, (a) What is the empirical formula of cyclopropane? How does it differ from that of propane? (b) The three carbon atoms are necessarily in a plane. What do the different wedges mean? (c) What change would you make to the structure shown to illustrate chlorocyclopropane? Are there isomers of chlorocyclopropane?

Problem 107AE Elements in the same group of the periodic table often form oxyanions with the same general formula. The anions are also named in a similar fashion. Based on these observations, suggest a chemical formula or name, as appropriate, for each of the following ions: (a) BrO? , (b4?SeO? , (c) a3?enate ion, (d) hydrogen tellurate ion.

Problem 108 Carbonic acid occurs in carbonated beverages. When allowed to react with lithium hydroxide, it produces lithium carbonate. Lithium carbonate is used to treat depression and bipolar disorder. Write chemical formulas for carbonic acid, lithium hydroxide, and lithium carbonate.

Problem 109AE Give the chemical names of each of the following familiar compounds: (a) NaCl (table salt), (b) NaHCO? (baking soda),3?c) NaOCl (in many bleaches), (d) NaOH (caustic soda), (e) (NH? )? CO? (4? 2?ing3?alts), (f) CaSO? (plaster of Paris). 4?

Problem 110AE Many familiar substances have common, unsystematic names. For each of the following, give the correct systematic name: (a) saltpeter, KNO? , (b) so3? ash, Na? CO? , (c) lime,2?aO, 3?) muriatic acid, HCl, (e) Epsom salts, MgSO? , (f) milk of magnesia, Mg(OH)? . 4? 2?

Problem 112AE In what part of the atom does the strong nuclear force operate?

Problem 111AE Because many ions and compounds have very similar names, there is great potential for confusing them. Write the correct chemical formulas to distinguish between (a) calcium sulfide and calcium hydrogen sulfide, (b) hydrobromic acid and bromic acid, (c) aluminum nitride and aluminum nitrite, (d) iron(ll) oxide and iron(lll) oxide, (e) ammonia and ammonium ion, (f) potassium sulfite and potassium bisulfite, (g) mercurous chloride and mercuric chloride, (h) chloric acid and perchloric acid.

What is scanning tunneling microscopy? How does it work?

Summarize the history of the atomic idea. How was Dalton able to convince others to accept an idea that had been controversial for 2000 years?

State and explain the law of conservation of mass.

State and explain the law of definite proportions.

What are the main ideas in Dalton’s atomic theory? How do they help explain the laws of conservation of mass, of constant composition, and of definite proportions?

State and explain the law of multiple proportions. How is the law of multiple proportions different from the law of definite proportions?

How and by whom was the electron discovered? What basic properties of the electron were reported with its discovery?

Explain Millikan’s oil drop experiment and how it led to the measurement of the electron’s charge. Why is the magnitude of the charge of the electron so important?

Describe the plum-pudding model of the atom.

Describe Rutherford’s gold foil experiment. How did the experiment prove that the plum-pudding model of the atom was wrong?

Describe Rutherford’s nuclear model of the atom. What was revolutionary about his model?

If matter is mostly empty space, as suggested by Rutherford, then why does it appear so solid?

List the three subatomic particles that compose atoms and give the basic properties (mass and charge) of each.

What defines an element?

Explain the difference between Z (the atomic number) and A (the mass number).

Where do elements get their names?

What are isotopes? What is percent natural abundance of isotopes?

Describe the two different notations used to specify isotopes and give an example of each.

What is an ion? A cation? An anion?

State the periodic law. How did the periodic law lead to the periodic table?

What are the characteristic properties of metals, nonmetals, and metalloids?

What are the characteristic properties of each group? a. noble gases b. alkali metals c. alkaline earth metals d. halogens

How do you predict the charges of ions formed by main-group elements?

What is atomic mass? How is it calculated?

Explain how a mass spectrometer works.

What kind of information can be determined from a mass spectrum?

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

Why is the mass corresponding to a mole of one element different from the mass corresponding to a mole of another element?

A hydrogen-filled balloon was ignited and 1.50 g of hydrogen reacted with 12.0 g of oxygen. How many grams of water vapor formed? (Assume that water vapor is the only product.)

Classify each element as an alkali metal, alkaline earth metal, halogen, or noble gas. a. sodium b. iodine c. calcium d. barium e. krypton

Classify each element as an alkali metal, alkaline earth metal, halogen, or noble gas. a. F b. Sr c. K d. Ne e. At

Which pair of elements do you expect to be most similar? Why? a. N and Ni b. Mo and Sn c. Na and Mg d. Cl and F e. Si and P

Which pair of elements do you expect to be most similar? Why? a. nitrogen and oxygen b. titanium and gallium c. lithium and sodium d. germanium and arsenic e. argon and bromine

Gallium has two naturally occurring isotopes with the following masses and natural abundances: Sketch the mass spectrum of Gallium.

Problem 86 Naming Inorganic Compounds; Some Simple Organic Compounds (Sections) Draw the structural formulas for three isomers of pentane, C? H? . 5? 12?

Calculate the number of atoms in each sample. a. 5.18 g P b. 2.26 g Hg c. 1.87 g Bi d. 0.082 g Sr

Problem 88 The natural abundance of 3He is 0.000137%. (a) How many protons, neutrons, and electrons are in an atom of ? He? 3? (b) Based on the sum of the masses of their subatomic particles, which is expected to be more massive, an atom of ? He or an atom of ? H (which is also called tritium)? (c) Based on your answer to part (b), what would need to be the precision of a mass 3 ? +? 3? +? spectrometer that is able to differentiate between peaks that are due to ? He? and ? H? ?

What is the mass number of an iron atom that has 28 neutrons?

Calculate the number of neutrons in 239Pu

For each of the following species, determine the number of protons and the number of neutrons in the nucleus: 2 3 He, 2 4 He, 12 24Mg, 25 12Mg, 48 22Ti, 79 35Br, 195 78Pt

Indicate the number of protons, neutrons, and electrons in each of the following species: 15 7N, 33 16S, 63 29Cu, 84 38Sr, 130 56Ba, 186 74W, 202 80Hg

Write the appropriate symbol for each of the following isotopes: (a) Z 5 11, A 5 23; (b) Z 5 28, A 5 64.

Write the appropriate symbol for each of the following isotopes: (a) Z 5 74, A 5 186; (b) Z 5 80, A 5 201.

What is the periodic table, and what is its significance in the study of chemistry?

State two differences between a metal and a nonmetal.

Write the names and symbols for four elements in each of the following categories: (a) nonmetal, (b) metal, (c) metalloid.

Define, with two examples, the following terms: (a) alkali metals, (b) alkaline earth metals, (c) halogens, (d) noble gases.

Elements whose names end with -ium are usually metals; sodium is one example. Identify a nonmetal whose name also ends with -ium.

Describe the changes in properties (from metals to nonmetals or from nonmetals to metals) as we move (a) down a periodic group and (b) across the periodic table from left to right.

Consult a handbook of chemical and physical data (ask your instructor where you can locate a copy of the handbook) to find (a) two metals less dense than water, (b) two metals more dense than mercury, (c) the densest known solid metallic element, (d) the densest known solid nonmetallic element.

Group the following elements in pairs that you would expect to show similar chemical properties: K, F, P, Na, Cl, and N.

What is the difference between an atom and a molecule?

What are allotropes? Give an example. How are allotropes different from isotopes?

Describe the two commonly used molecular models.

Give an example of each of the following: (a) a monatomic cation, (b) a monatomic anion, (c) a polyatomic cation, (d) a polyatomic anion.

Which of the following diagrams represent diatomic molecules, polyatomic molecules, molecules that are not compounds, molecules that are compounds, or an elemental form of the substance? (a) (b) (c)

Which of the following diagrams represent diatomic molecules, polyatomic molecules, molecules that are not compounds, molecules that are compounds, or an elemental form of the substance? (a) ( (b) c)

Identify the following as elements or compounds: NH3, N2, S8, NO, CO, CO2, H2, SO2.

Give two examples of each of the following: (a) a diatomic molecule containing atoms of the same element, (b) a diatomic molecule containing atoms of different elements, (c) a polyatomic molecule containing atoms of the same element, (d) a polyatomic molecule containing atoms of different elements.

Give the number of protons and electrons in each of the following common ions: Na1, Ca21, Al31, Fe21, I 2, F2, S22, O22, and N32

Give the number of protons and electrons in each of the following common ions: K1, Mg21, Fe31, Br2, Mn21, C42, Cu21.

What does a chemical formula represent? What is the ratio of the atoms in the following molecular formulas? (a) NO, (b) NCl3, (c) N2O4, (d) P4O6

Define molecular formula and empirical formula. What are the similarities and differences between the empirical formula and molecular formula of a compound?

Give an example of a case in which two molecules have different molecular formulas but the same empirical formula

What does P4 signify? How does it differ from 4P?

What is an ionic compound? How is electrical neutrality maintained in an ionic compound?

Explain why the chemical formulas of ionic compounds are usually the same as their empirical formulas.

Write the formulas for the following ionic compounds: (a) sodium oxide, (b) iron sulfide (containing the Fe21 ion), (c) cobalt sulfate (containing the Co31 and SO4 22 ions), and (d) barium fluoride. (Hint: See Figure 2.11.)

Write the formulas for the following ionic compounds: (a) copper bromide (containing the Cu1 ion), (b) manganese oxide (containing the Mn31 ion), (c) mercury iodide (containing the Hg2 21 ion), and (d) magnesium phosphate (containing the PO4 32 ion). (Hint: See Figure 2.11.)

What are the empirical formulas of the following compounds? (a) C2N2, (b) C6H6, (c) C9H20, (d) P4O10, (e) B2H6

What are the empirical formulas of the following compounds? (a) Al2Br6, (b) Na2S2O4, (c) N2O5, (d) K2Cr2O7

Write the molecular formula of glycine, an amino acid present in proteins. The color codes are: black (carbon), blue (nitrogen), red (oxygen), and gray (hydrogen).HCNO

Write the molecular formula of ethanol. The color codes are: black (carbon), red (oxygen), and gray (hydrogen). H C O

Which of the following compounds are likely to be ionic? Which are likely to be molecular? SiCl4, LiF, BaCl2, B2H6, KCl, C2H4

Which of the following compounds are likely to be ionic? Which are likely to be molecular? CH4, NaBr, BaF2, CCl4, ICl, CsCl, NF3

What is the difference between inorganic compounds and organic compounds?

What are the four major categories of inorganic compounds?

Give an example each for a binary compound and a ternary compound.

What is the Stock system? What are its advantages over the older system of naming cations?

Explain why the formula HCl can represent two different chemical systems.

Define the following terms: acids, bases, oxoacids, oxoanions, and hydrates.

Name these compounds: (a) Na2CrO4, (b) K2HPO4, (c) HBr (gas), (d) HBr (in water), (e) Li2CO3, (f) K2Cr2O7, (g) NH4NO2, (h) PF3, (i) PF5, (j) P4O6, (k) CdI2, (l) SrSO4, (m) Al(OH)3, (n) Na2CO3 ? 10H2O.

Name these compounds: (a) KClO, (b) Ag2CO3, (c) FeCl2, (d) KMnO4, (e) CsClO3, (f) HIO, (g) FeO, (h) Fe2O3, (i) TiCl4, ( j) NaH, (k) Li3N, (l) Na2O, (m) Na2O2, (n) FeCl3 ? 6H2O.

Write the formulas for the following compounds: (a) rubidium nitrite, (b) potassium sulfide, (c) sodium hydrogen sulfide, (d) magnesium phosphate, (e) calcium hydrogen phosphate, (f) potassium dihydrogen phosphate, (g) iodine heptafluoride, (h) ammonium sulfate, (i) silver perchlorate, (j) boron trichloride.

Write the formulas for the following compounds: (a) copper(I) cyanide, (b) strontium chlorite, (c) perbromic acid, (d) hydroiodic acid, (e) disodium ammonium phosphate, (f) lead(II) carbonate, (g) tin(II) fluoride, (h) tetraphosphorus decasulfide, (i) mercury(II) oxide, (j) mercury(I) iodide, (k) selenium hexafluoride.

Sulfur (S) and fluorine (F) form several different compounds. One of them, SF6, contains 3.55 g of F for every gram of S. Use the law of multiple proportions to determine n, which represents the number of F atoms in SFn, given that it contains 2.37 g of F for every gram of S.

Name the following compounds. B Al Br F O N

Pair the following species that contain the same number of electrons: Ar, Sn41, F2, Fe31, P32, V, Ag1, N32.

Write the correct symbols for the atoms that contain: (a) 25 protons, 25 electrons, and 27 neutrons; (b) 10 protons, 10 electrons, and 12 neutrons; (c) 47 protons, 47 electrons, and 60 neutrons; (d) 53 protons, 53 electrons, and 74 neutrons; (e) 94 protons, 94 electrons, and 145 neutrons.

A sample of a uranium compound is found to be losing mass gradually. Explain what is happening to the sample.

In which one of the following pairs do the two species resemble each other most closely in chemical properties? Explain. (a) 1 1 H and 1 1 H1, (b) 14 7N and 14 7N32, (c) 12 6C and 13 6C.

One isotope of a metallic element has mass number 65 and 35 neutrons in the nucleus. The cation derived from the isotope has 28 electrons. Write the symbol for this cation.

One isotope of a nonmetallic element has mass number 127 and 74 neutrons in the nucleus. The anion derived from the isotope has 54 electrons. Write the symbol for this anion

Determine the molecular and empirical formulas of the compounds shown here. (Black spheres are carbon and gray spheres are hydrogen.)(a) (b) (c) (d)

What is wrong with or ambiguous about the phrase four molecules of NaCl?

The following phosphorus sulfides are known: P4S3, P4S7, and P4S10. Do these compounds obey the law of multiple proportions?

Which of the following are elements, which are molecules but not compounds, which are compounds but not molecules, and which are both compounds and molecules? (a) SO2, (b) S8, (c) Cs, (d) N2O5, (e) O, (f) O2, (g) O3, (h) CH4, (i) KBr, (j) S, (k) P4, (l) LiF

The following table gives numbers of electrons, protons, and neutrons in atoms or ions of a number of elements. Answer the following: (a) Which of the species are neutral? (b) Which are negatively charged? (c) Which are positively charged? (d) What are the conventional symbols for all the species? Atom or Ion of Element A B C D E F G Number of electrons 5 10 18 28 36 5 9 Number of protons 5 7 19 30 35 5 9 Number of neutrons 5 7 20 36 46 6 10

Identify the elements represented by the following symbols and give the number of protons and neutrons in each case: (a) 20 10X, (b) 63 29X, (c) 107 47X, (d) 182 74X, (e) 203 84X, (f) 234 94X.

Each of the following pairs of elements will react to form an ionic compound. Write the formulas and name these compounds: (a) barium and oxygen, (b) calcium and phosphorus, (c) aluminum and sulfur, (d) lithium and nitrogen.

Match the descriptions [(a)(h)] with each of the following elements: P, Cu, Kr, Sb, Cs, Al, Sr, Cl. (a) A transition metal, (b) a nonmetal that forms a 23 ion, (c) a noble gas, (d) an alkali metal, (e) a metal that forms a 13 ion, (f) a metalloid, (g) an element that exists as a diatomic gas molecule, (h) an alkaline earth metal.

Explain why anions are always larger than the atoms from which they are derived, whereas cations are always smaller than the atoms from which they are derived. (Hint: Consider the electrostatic attraction between protons and electrons.)

(a) Describe Rutherfords experiment and how it led to the structure of the atom. How was he able to estimate the number of protons in a nucleus from the scattering of the particles? (b) Consider the 23Na atom. Given that the radius and mass of the nucleus are 3.04 3 10215 m and 3.82 3 10223 g, respectively, calculate the density of the nucleus in g/cm3 . The radius of a 23Na atom is 186 pm. Calculate the density of the space occupied by the electrons in the sodium atom. Do your results support Rutherfords model of an atom? [The volume of a sphere of radius r is (4/3)r 3 .]

Caffeine, shown here, is a psychoactive stimulant drug. Write the molecular formula and empirical formula of the compound.OHNC

Acetaminophen, shown here, is the active ingredient in Tylenol. Write the molecular formula and empirical formula of the compound.CONH

What is wrong with the chemical formula for each of the following compounds: (a) magnesium iodate [Mg(IO4)2], (b) phosphoric acid (H3PO3), (c) barium sulfite (BaS), (d) ammonium bicarbonate (NH3HCO3)?

What is wrong with the names (in parentheses) for each of the following compounds: SnCl4 (tin chloride), (b) Cu2O [copper(II) oxide], (c) Co(NO3)2 (cobalt nitrate), (d) Na2Cr2O7 (sodium chromate)?

Fill in the blanks in the following table. Symbol 54 26Fe21 Protons 5 79 86 Neutrons 6 16 117 136 Electrons 5 18 79 Net charge 23 0

(a) Which elements are most likely to form ionic compounds? (b) Which metallic elements are most likely to form cations with different charges?

Write the formula of the common ion derived from each of the following: (a) Li, (b) S, (c) I, (d) N, (e) Al, (f) Cs, (g) Mg

Which of the following symbols provides more information about the atom: 23Na or 11Na? Explain

Write the chemical formulas and names of binary acids and oxoacids that contain Group 7A elements. Do the same for elements in Groups 3A, 4A, 5A, and 6A

Of the 118 elements known, only two are liquids at room temperature (25C). What are they? (Hint: One element is a familiar metal and the other element is in Group 7A.)

For the noble gases (the Group 8A elements), 4 2He, 20 10Ne, 40 18Ar, 84 36Kr, and 132 54Xe, (a) determine the number of protons and neutrons in the nucleus of each atom, and (b) determine the ratio of neutrons to protons in the nucleus of each atom. Describe any general trend you discover in the way this ratio changes with increasing atomic number

List the elements that exist as gases at room temperature. (Hint: Most of these elements can be found in Groups 5A, 6A, 7A, and 8A.)

The Group 1B metals, Cu, Ag, and Au, are called coinage metals. What chemical properties make them specially suitable for making coins and jewelry?

The elements in Group 8A of the periodic table are called noble gases. Can you suggest what noble means in this context?

The formula for calcium oxide is CaO. What are the formulas for magnesium oxide and strontium oxide?

A common mineral of barium is barytes, or barium sulfate (BaSO4). Because elements in the same periodic group have similar chemical properties, we might expect to find some radium sulfate (RaSO4) mixed with barytes since radium is the last member of Group 2A. However, the only source of radium compounds in nature is in uranium minerals. Why?

List five elements each that are (a) named after places, (b) named after people, (c) named after a color. (Hint: See Appendix 1.)

One isotope of a nonmetallic element has mass number 77 and 43 neutrons in the nucleus. The anion derived from the isotope has 36 electrons. Write the symbol for this anion

Fluorine reacts with hydrogen (H) and deuterium (D) to form hydrogen fluoride (HF) and deuterium fluoride (DF), where deuterium (2 1H) is an isotope of hydrogen. Would a given amount of fluorine react with different masses of the two hydrogen isotopes? Does this violate the law of definite proportion? Explain.

Predict the formula and name of a binary compound formed from the following elements: (a) Na and H, (b) B and O, (c) Na and S, (d) Al and F, (e) F and O, (f) Sr and Cl.

Identify each of the following elements: (a) a halogen whose anion contains 36 electrons, (b) a radioactive noble gas with 86 protons, (c) a Group 6A element whose anion contains 36 electrons, (d) alkali metal cation that contains 36 electrons, (e) a Group 4A cation that contains 80 electrons

Write the molecular formulas for and names of the following compounds. F Br PCl S N

Show the locations of (a) alkali metals, (b) alkaline earth metals, (c) the halogens, and (d) the noble gases in the following outline of a periodic table. Also draw dividing lines between metals and metalloids and between metalloids and nonmetals. 1A 2A 3A 4A 5A 6A 7A 8A

Fill the blanks in the following table. Cation Anion Formula Name Magnesium bicarbonate SrCl2 Fe31 NO2 2 Manganese(II) chlorate SnBr4 Co21 PO4 32 Hg2 21 I2 Cu2CO3 Lithium nitride Al31 S22

Some compounds are better known by their common names than by their systematic chemical names. Give the chemical formulas of the following substances: (a) dry ice, (b) table salt, (c) laughing gas, (d) marble (chalk, limestone), (e) quicklime, (f) slaked lime, (g) baking soda, (h) washing soda, (i) gypsum, (j) milk of magnesia.

On p. 40 it was pointed out that mass and energy are alternate aspects of a single entity called massenergy. The relationship between these two physical quantities is Einsteins famous equation, E 5 mc2 , where E is energy, m is mass, and c is the speed of light. In a combustion experiment, it was found that 12.096 g of hydrogen molecules combined with 96.000 g of oxygen molecules to form water and released 1.715 3 103 kJ of heat. Calculate the corresponding mass change in this process and comment on whether the law of conservation of mass holds for ordinary chemical processes. (Hint: The Einstein equation can be used to calculate the change in mass as a result of the change in energy. 1 J 5 1 kg m2 /s2 and c 5 3.00 3 108 m/s.)

Draw all possible structural formulas of the following hydrocarbons: CH4, C2H6, C3H8, C4H10, and C5H12.

(a) Assuming nuclei are spherical in shape, show that its radius r is proportional to the cube root of mass number (A). (b) In general, the radius of a nucleus is given by r 5 r0A1/3, where r0 is a proportionality constant given by 1.2 3 10215 m. Calculate the volume of the 7 3Li nucleus. (c) Given that the radius of a Li atom is 152 pm, calculate the fraction of the atoms volume occupied by the nucleus. Does your result support Rutherfords model of an atom?

Draw two different structural formulas based on the molecular formula C2H6O. Is the fact that you can have more than one compound with the same molecular formula consistent with Daltons atomic theory?

Ethane and acetylene are two gaseous hydrocarbons. Chemical analyses show that in one sample of ethane, 2.65 g of carbon are combined with 0.665 g of hydrogen, and in one sample of acetylene, 4.56 g of carbon are combined with 0.383 g of hydrogen. (a) Are these results consistent with the law of multiple proportions? (b) Write reasonable molecular formulas for these compounds.

A cube made of platinum (Pt) has an edge length of 1.0 cm. (a) Calculate the number of Pt atoms in the cube. (b) Atoms are spherical in shape. Therefore, the Pt atoms in the cube cannot fill all of the available space. If only 74 percent of the space inside the cube is taken up by Pt atoms, calculate the radius in picometers of a Pt atom. The density of Pt is 21.45 g/cm3 and the mass of a single Pt atom is 3.240 3 10222 g. [The volume of a sphere of radius r is (4/3)r 3 .]

A monatomic ion has a charge of 12. The nucleus of the parent atom has a mass number of 55. If the number of neutrons in the nucleus is 1.2 times that of the number of protons, what is the name and symbol of the element?

In the following 2 3 2 crossword, each letter must be correct four ways: horizontally, vertically, diagonally, and by itself. When the puzzle is complete, the four spaces will contain the overlapping symbols of 10 elements. Use capital letters for each square. There is only one correct solution.* 1 2 3 4 Horizontal 12: Two-letter symbol for a metal used in ancient times 34: Two-letter symbol for a metal that burns in air and is found in Group 5A Vertical 13: Two-letter symbol for a metalloid 24: Two-letter symbol for a metal used in U.S. coins Single Squares 1: A colorful nonmetal 2: A colorless gaseous nonmetal 3: An element that makes fireworks green 4: An element that has medicinal uses Diagonal 14: Two-letter symbol for an element used in electronics 23: Two-letter symbol for a metal used with Zr to make wires for superconducting magnets

Name the following acids. S C N H Cl O

Calculate the density of the nucleus of a 56 26Fe atom, given that the nuclear mass is 9.229 3 10223 g. From your result, comment on the fact that any nucleus containing more than one proton must have neutrons present as well. (Hint: See Problem 2.106.)

Element X reacts with element Y to form an ionic compound containing X41 and Y22 ions. Write a formula for the compound and suggest in which periodic groups these elements are likely to be found. Name a representative compound.

Methane, ethane, and propane are shown in Table 2.8. Show that the following data are consistent with the law of multiple proportions. Mass of Carbon Mass of Hydrogen in 1 g Sample in 1 g Sample Methane 0.749 g 0.251 g Ethane 0.799 g 0.201 g Propane 0.817 g 0.183 g

In the Rutherford scattering experiment, an particle is heading directly toward a gold nucleus. The particle will come to a halt when its kinetic energy is completely converted to electrical potential energy. When this happens, how close will the particle with a kinetic energy of 6.0 3 10214 J be from the nucleus? [According to Coulombs law, the electrical potential energy between two charged particles is E 5 kQ1Q2/r, where Q1 and Q2 are the charges (in coulombs) of the particle and the gold nucleus, r is the distance of separation in meters, and k is a constant equal to 9.0 3 109 kg ? m3 /s2 ? C2 . Joule (J) is the unit of energy where 1 J 5 1 kg ? m2 /s2 .]

Estimate the relative sizes of the following species: Li, Li1, Li2

Compare the atomic size of the following two magnesium isotopes: 24Mg and 26Mg.

Using visible light, we humans cannot see any object smaller than 2 3 1025 cm with an unaided eye. Roughly how many silver atoms must be lined up for us to see the atoms?

If the size of the nucleus of an atom were that of a pea, how far would the electrons be (on average) from the nucleus in meters?

Sodium and potassium are roughly equal in natural abundance in Earths crust and most of their compounds are soluble. However, the composition of seawater is much higher in sodium than potassium. Explain

One technique proposed for recycling plastic grocery bags is to heat them at 700C and high pressure to form carbon microspheres that can be used in a number of applications. Electron microscopy shows some representative carbon microspheres obtained in this manner, where the scale is given in the bottom right corner of the figure. Determine the number of carbon atoms in a typical carbon microsphere. 5 m

Problem 1SAQ Two samples of a compound containing elements A and B were decomposed. The first sample produced 15 g of A and 35 g of B. The second sample produced 25 g of A and what mass of B? a) 11 g b) 58 g c) 21 g d) 45 g

Problem 2SAQ A compound containing only carbon and hydrogen has a carbon-to-hydrogen mass ratio of 11.89. Which carbonto- hydrogen mass ratio is possible for another compound composed only of carbon and hydrogen? a) 2.50 b) 3.97 c) 4.66 d) 7.89

Problem 3SAQ Wiich idea came out of Rutherford’s gold foil experiment? a) Atoms contain protons and neutrons. b) Matter is composed of atoms. c) Elements have isotopes. d) Atoms are mostly empty space.

A student re-creates the Millikan oil drop experiment and tabulates the relative charges of the oil drops in terms of a constant, . What charge for the electron (in terms of ) is consistent with this data?

Problem 5SAQ Determine the number of protons and neutrons in the isotope Fe-53. a) 26 protons and 58 neutrons b) 32 protons and 26 neutrons c) 26 protons and 32 neutrons d) 53 protons and 53 neutrons

An isotope of an element contains 82 protons and 122 neutrons. What is the symbol for the isotope?

Determine the number of electrons in the Cr3+ ion. a) 24 electrons b) 27 electrons c) 3 electrons d) 21 electrons

Problem 8SAQ Which pair of elements do you expect to be most similar in their chemical properties? a) K and Fe b) O and Si c) Ne and N d) Br and I

Which element is not a main-group element? a. Se b. Mo c. Sr d. Ba

What is the charge of the ion most commonly formed by S? a. 2+ b. + c. - d. 2-

Problem 11SAQ A naturally occurring sample of an element contains only two isotopes. The first isotope has a mass of 68.9255 amu and a natural abundance of 60.11 %. The second isotope has a mass of 70.9247 amu. Find the atomic mass of the element. a) 70.13 amu b) 69.72 amu c) 84.06 amu d) 69.93 amu

Problem 12SAQ Which sample contains the greatest number of atoms? a) 14 g C b) 49 g Cr c) 102 g Ag d) 202 g Pb

Determine the number of atoms in 1.85 mL of mercury. (The density of mercury is 13.5 g/mL.) a) 3.02 x 1027 atoms b) 4.11 x 1020 atoms c) 7.50 x 1022 atoms d) 1.50 x 1025 atoms

A 20.0 g sample of an element contains 4.95 x 1023 atoms. Identify the element. a) Cr b) O c) Mg d) Fe

Copper has two naturally occurring isotopes with masses 62.94 amu and 64.93 amu and has an atomic mass of 63.55 amu. Which mass spectrum is most likely to correspond to a naturally occurring sample of copper?

An automobile gasoline tank holds 21 kg of gasoline. When the gasoline burns, 84 kg of oxygen is consumed, and carbon dioxide and water are produced. What is the total combined mass of carbon dioxide and water that is produced?

Magnesium has three naturally occurring isotopes with the following masses and natural abundances: Sketch the mass spectrum of magnesium.

The atomic mass of fluorine is 18.998 amu and its mass spectrum shows a large peak at this mass. The atomic mass of chlorine is 35.45 amu, yet the mass spectrum of chlorine does not show a peak at this mass. Explain the difference.

Silicon has three naturally occurring isotopes (Si-28, Si-29, and Si-30). The mass and natural abundance of Si-28 are 27.9769 amu and 92.2%, respectively. The mass and natural abundance of Si-29 are 28.9765 amu and 4.67%, respectively. Find the mass and natural abundance of Si-30.

Use the mass spectrum of europium to determine the atomic mass of europium.

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

What is the amount, in moles, of each elemental sample? a. 11.8 g Ar b. 3.55 g Zn c. 26.1 g Ta d. 0.211 g Li

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

What is the mass of 4.91 x 1021 platinum atoms?

Calculate the number of atoms in each sample. a. 14.955 g Cr b. 39.733 g S c. 12.899 g Pt d. 97.552 g Sn

Calculate the mass, in grams, of each sample. a. 1.1 x 1023 gold atoms b. 2.82 x 1022 helium atoms c. 1.8 x 1023 lead atoms d. 7.9 x 1021 uranium atoms

Calculate the mass, in kg, of each sample. a. 7.55 x 1026 cadmium atoms b. 8.15 x 1027 nickel atoms c. 1.22 x 1027 manganese atoms d. 5.48 x 1029 lithium atoms

How many carbon atoms are there in a diamond (pure carbon) with a mass of 52 mg?

How many helium atoms are there in a helium blimp containing 536 kg of helium?

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

Using scanning tunneling microscopy, scientists at IBM wrote the initials of their company with 35 individual xenon atoms (as shown below). Calculate the total mass of these letters in grams.

A 7.83 g sample of HCN contains 0.290 g of H and 4.06 g of N. Find the mass of carbon in a sample of HCN with a mass of 3.37 g.

The ratio of sulfur to oxygen by mass in SO2 is 1.0:1.0. a. Find the ratio of sulfur to oxygen by mass in SO3. b. Find the ratio of sulfur to oxygen by mass in S2O.

The ratio of oxygen to carbon by mass in carbon monoxide is 1.33:1.00. Find the formula of an oxide of carbon in which the ratio by mass of oxygen to carbon is 2.00:1.00.

The ratio of the mass of a nitrogen atom to the mass of an atom of 12C is 7:6 and the ratio of the mass of nitrogen to oxygen in N2O is 7:4. Find the mass of 1 mol of oxygen atoms.

An \(\alpha\) particle, \({ }^4 \mathrm{He}^{2+}\), has a mass of 4.00151 amu. Find the value of its charge-to-mass ratio in \(\mathrm{C} / \mathrm{kg}\).

Naturally occurring iodine has an atomic mass of 126.9045. A 12.3849 g sample of iodine is accidentally contaminated with an additional 1.00070 g of 129I, a synthetic radioisotope of iodine used in the treatment of certain diseases of the thyroid gland. The mass of 129I is 128.9050 amu. Find the apparent “atomic mass” of the contaminated iodine.

Use the mass spectrum of lead to estimate the atomic mass of lead. Estimate the mass and percent intensity values from the graph to three significant figures.

Use the mass spectrum of mercury to estimate the atomic mass of mercury. Estimate the masses and percent intensity values from the graph to three significant figures.

Nuclei with the same number of neutrons but different mass numbers are called isotones. Write the symbols of four isotones of \({ }^{236} \mathrm{Th}\).

Fill in the blanks to complete the table.

Neutron stars are composed of solid nuclear matter, primarily neutrons. Assume the radius of a neutron is approximately 1.0 x 10-13cm . Calculate the density of a neutron. [Hint : For a sphere V = (4/3)r3.] Assuming that a neutron star has the same density as a neutron, calculate the mass (in kg) of a small piece of a neutron star the size of a spherical pebble with a radius of 0.10 mm.

Fill in the blanks to complete the table.

Carbon-12 contains six protons and six neutrons. The radius of the nucleus is approximately 2.7 fm (femtometers) and the radius of the atom is approximately 70 pm (picometers). Calculate the volume of the nucleus and the volume of the atom. What percentage of the carbon atom’s volume is occupied by the nucleus? (Assume two significant figures.)

A penny has a thickness of approximately 1.0 mm. If you stacked Avogadro’s number of pennies one on top of the other on Earth’s surface, how far would the stack extend (in km)? [For comparison, the sun is about 150 million km from Earth and the nearest star (Proxima Centauri) is about 40 trillion km from Earth.]

Consider the stack of pennies in the previous problem. How much money (in dollars) would this represent? If this money were equally distributed among the world’s population of 6.5 billion people, how much would each person receive? Would each person be a millionaire? Billionaire? Trillionaire?

The mass of an average blueberry is 0.75 g and the mass of an automobile is 2.0 x 103 kg . Find the number of automobiles whose total mass is the same as 1.0 mol of blueberries.

Suppose that atomic masses were based on the assignment of a mass of 12.000 g to 1 mol of carbon, rather than 1 mol of 12C. What would the atomic mass of oxygen be? (The atomic masses of carbon and oxygen based on the assignment of 12.000 g to 1 mol of 12C are 12.011 amu and 15.9994 amu, respectively.)

A pure titanium cube has an edge length of 2.78 in. How many titanium atoms does it contain? Titanium has a density of 4.50 g/cm3.

A pure copper sphere has a radius of 0.935 in. How many copper atoms does it contain? [The volume of a sphere is (4/3)r3 and the density of copper is 8.96 g/cm3.]

Boron has only two naturally occurring isotopes. The mass of boron-10 is 10.01294 amu and the mass of boron-11 is 11.00931 amu. Calculate the relative abundances of the two isotopes.

Lithium has only two naturally occurring isotopes. The mass of lithium-6 is 6.01512 amu and the mass of lithium-7 is 7.01601 amu. Calculate the relative abundances of the two isotopes.

Common brass is a copper and zinc alloy containing 37.0% zinc by mass and having a density of 8.48 g/cm3. A fitting composed of common brass has a total volume of 112.5 cm3. How many atoms (copper and zinc) does the fitting contain?

A 67.2 g sample of a gold and palladium alloy contains 2.49 x 1023 atoms. What is the composition (by mass) of the alloy?

Naturally occurring chlorine is composed of two isotopes: 75.76% Cl-35 (mass 34.9688 amu) and 24.24% Cl-37 (mass 36.9659 amu). Naturally occurring oxygen is composed of three isotopes: 99.757% O-16 (mass 15.9949 amu), 0.038% O-17 (mass 16.9991 amu), and 0.205% O-18 (mass 17.9991 amu). The compound dichlorine monoxide is composed of two chlorine atoms and one oxygen atom bonded together to form the Cl2O molecule. How many Cl2O molecules of different masses naturally exist? Give the masses of the three most abundant Cl2O molecules.

Silver is composed of two naturally occurring isotopes: Ag-107 (51.839%) and Ag-109. The ratio of the masses of the two isotopes is 1.0187. What is the mass of Ag-107?

The U.S. Environmental Protection Agency (EPA) sets limits on healthful levels of air pollutants. The maximum level that the EPA considers safe for lead air pollution is 1.5 g/m3. If your lungs were filled with air containing this level of lead, how many lead atoms would be in your lungs? (Assume a total lung volume of 5.50 L.)

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

In Section 2.9 , it was stated that 1 mol of sand grains would cover the state of Texas to several feet. Estimate how many feet by assuming that the sand grains are roughly cube-shaped, each one with an edge length of 0.10 mm. Texas has a land area of 268,601 square miles.

Use the concepts in this chapter to obtain an estimate for the number of atoms in the universe. Make the following assumptions: (a) All of the atoms in the universe are hydrogen atoms in stars. (This is not a ridiculous assumption because over three-fourths of the atoms in the universe are in fact hydrogen. Gas and dust between the stars represent only about 15% of the visible matter of our galaxy, and planets compose a far tinier fraction.) (b) The sun is a typical star composed of pure hydrogen with a density of 1.4 g/cm3 and a radius of 7 x 108m . (c) Each of the roughly 100 billion stars in the Milky Way galaxy contains the same number of atoms as our sun. (d) Each of the 10 billion galaxies in the visible universe contains the same number of atoms as our Milky Way galaxy.

On the previous page is a representation of 50 atoms of a fictitious element called westmontium (Wt). The red spheres represent Wt-296, the blue spheres Wt-297, and the green spheres Wt-298. a. Assuming that the sample is statistically representative of a naturally occurring sample, calculate the percent natural abundance of each Wt isotope. b. Draw the mass spectrum for a naturally occurring sample of Wt. c. The mass of each Wt isotope is measured relative to C-12 and tabulated next. Use the mass of C-12 to convert each of the masses to amu and calculate the atomic mass of Wt.

The ratio of oxygen to nitrogen by mass in NO2 is 2.29. The ratio of fluorine to nitrogen by mass in NF3 is 4.07. Find the ratio of oxygen to fluorine by mass in OF2.

Naturally occurring cobalt consists of only one isotope, 59Co, whose relative atomic mass is 58.9332. A synthetic radioactive isotope of cobalt, 60Co, has a relative atomic mass of 59.9338 and is used in radiation therapy for cancer. A 1.5886 g sample of cobalt has an apparent “atomic mass” of 58.9901. Find the mass of 60Co in this sample.

A 7.36 g sample of copper is contaminated with an additional 0.51 g of zinc. Suppose an atomic mass measurement was performed on this sample. What would be the measured atomic mass?

The ratio of the mass of O to the mass of N in N2O3 is 12:7. Another binary compound of nitrogen has a ratio of O to N of 16:7. What is its formula? What is the ratio of O to N in the next member of this series of compounds?

Naturally occurring magnesium has an atomic mass of 24.312 and consists of three isotopes. The major isotope is 24Mg, natural abundance 78.99%, relative atomic mass 23.98504. The next most abundant isotope is 26Mg, relative atomic mass 25.98259. The third most abundant isotope is 25Mg, whose natural abundance is in the ratio of 0.9083 to that of 26Mg. Find the relative atomic mass of 25Mg.

Which is an example of the law of multiple proportions? Explain. a. Two different samples of water are found to have the same ratio of hydrogen to oxygen. b. When hydrogen and oxygen react, the mass of water formed is exactly equal to the mass of hydrogen and oxygen that reacted. c. The mass ratio of oxygen to hydrogen in water is 8:1. The mass ratio of oxygen to hydrogen in hydrogen peroxide (a compound that only contains hydrogen and oxygen) is 16:1.

Lithium has two naturally occurring isotopes: Li-6 (natural abundance 7.5%) and Li-7 (natural abundance 92.5%). Using circles to represent protons and squares to represent neutrons, draw the nucleus of each isotope. How many Li-6 atoms would be present, on average, in a 1000-atom sample of lithium?

As we saw in the previous problem, lithium has two naturally occurring isotopes: Li-6 (natural abundance 7.5%; mass 6.0151 amu) and Li-7 (natural abundance 92.5%; mass 7.0160 amu). Without doing any calculations, determine which mass is closest to the atomic mass of Li. a. 6.00 amu b. 6.50 amu c. 7.00 amu

The mole is defined as the amount of a substance containing the same number of particles as exactly 12 grams of C-12. The amu is defined as 1>12 of the mass of an atom of C-12. Why is it important that both of these definitions reference the same isotope? What would be the result, for example, of defining the mole with respect to C-12, but the amu with respect to Ne-20?

Without doing any calculations, determine which of the samples contains the greatest amount of the element in moles. Which contains the greatest mass of the element? a. 55.0 g Cr b. 45.0 g Ti c. 60.0 g Zn

The atomic radii of the isotopes of an element are identical to one another. However, the atomic radii of the ions of an element are significantly different from the atomic radii of the neutral atom of the element. Explain.

Reread the speech, and think about the rhetorical strategies and style choices that help Queen Elizabeth convey her message. Think also about the persona she creates for herself and how that helps her achieve her purpose.

Read Winston Churchills first speech to the House of Commons as Prime Minister of Britain in May 1940. Describe the tone of the speech by using two adjectives or an adjective and an adverb; then explain why you chose those words, making specific reference to the text.

Why does Ellison think a book about bird-watching might be more edifying than a biography of Parker?

Why does Ellison say hung the bird on Charlie (para. 2) instead of nicknamed him?

What is the effect of Ellisons references to the story about the infant Jesus (para. 3)?

Why does Ellison provide the mockingbirds scientific name (Mimus polyglottos) (para. 4)?

How does Ellison manage to make this description of jazz sound so jazzy: by long-continued successions of notes and phrases, by swoops, bleats, echoes, rapidly repeated bebops I mean rebopped bebops . . . (para. 4)?

What is the effect of the dashes in the phrase above?

Why does Marx suggest that the source of Warner Bros. concerns about his film come from an ambitious young lawyer, referring to him as a pastyfaced legal adventurer (para. 10)?

Paragraph 23 consists of two rhetorical questions. How do they act as a transition to Kennedys call for action?

Find examples of rhetorical schemes such as anaphora (the repetition of a word or phrase at the beginning of successive phrases, clauses, or lines) and zeugma (one verb or adjective having multiple and incongruous objects).

Consider the speechs many examples of parallelism: born in this century, tempered by war, disciplined by a hard and bitter peace, proud of our ancient heritage (para. 3); pay any price, bear any burden, meet any hardship, support any friend, oppose any foe (para. 4). How do they lend themselves to Kennedys purpose?

Kennedy uses hortative sentences (language that urges or calls to action) in paragraphs 3 through 20: Let the word, Let both sides, and so on. Later, in paragraphs 25 and 26, he uses the imperative: ask and ask not. What is the difference between the two forms, and why did he start with one and end with the other?

What defines an element?

Explain the difference between Z (the atomic number) and A (the mass number).

Where do elements get their names?

What are isotopes? What is percent natural abundance of isotopes?

Describe the two different notations used to specify isotopes and give an example of each

What is an ion? A cation? An anion?

State the periodic law. How did the periodic law lead to the periodic table?

What are the characteristic properties of metals, nonmetals, and metalloids?

What are the characteristic properties of each group? a. noble gases b. alkali metals c. alkaline earth metals d. halogens

How do you predict the charges of ions formed by main-group elements?

What is atomic mass? How is it calculated?

Explain how a mass spectrometer works.

What kind of information can be determined from a mass spectrum?

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

Why is the mass corresponding to a mole of one element different from the mass corresponding to a mole of another element?

A hydrogen-filled balloon was ignited and 1.50 g of hydrogen reacted with 12.0 g of oxygen. How many grams of water vapor formed? (Assume that water vapor is the only product.)

An automobile gasoline tank holds 21 kg of gasoline. When the gasoline burns, 84 kg of oxygen is consumed, and carbon dioxide and water are produced. What is the total combined mass of carbon dioxide and water that is produced?

Two samples of carbon tetrachloride were decomposed into their constituent elements. One sample produced 38.9 g of carbon and 448 g of chlorine, and the other sample produced 14.8 g of carbon and 134 g of chlorine. Are these results consistent with the law of definite proportions? Show why or why not

Two samples of sodium chloride were decomposed into their constituent elements. One sample produced 6.98 g of sodium and 10.7 g of chlorine, and the other sample produced 11.2 g of sodium and 17.3 g of chlorine. Are these results consistent with the law of definite proportions? Explain your answer.

The mass ratio of sodium to fluorine in sodium fluoride is 1.21:1. A sample of sodium fluoride produces 28.8 g of sodium upon decomposition. How much fluorine (in grams) is formed?

Upon decomposition, one sample of magnesium fluoride produced 1.65 kg of magnesium and 2.57 kg of fluorine. A second sample produced 1.32 kg of magnesium. How much fluorine (in grams) did the second sample produce?

Two different compounds containing osmium and oxygen have the following masses of oxygen per gram of osmium: 0.168 and 0.3369 g. Show that these amounts are consistent with the law of multiple proportions.

Palladium forms three different compounds with sulfur. The mass of sulfur per gram of palladium in each compound is listed below. Show that these masses are consistent with the law of multiple proportions.

Sulfur and oxygen form both sulfur dioxide and sulfur trioxide. When samples of these were decomposed the sulfur dioxide produced 3.49 g oxygen and 3.50 g sulfur, while the sulfur trioxide produced 6.75 g oxygen and 4.50 g sulfur. Calculate the mass of oxygen per gram of sulfur for each sample and show that these results are consistent with the law of multiple proportions.

Sulfur and fluorine form several different compounds including sulfur hexafluoride and sulfur tetrafluoride. Decomposition of a sample of sulfur hexafluoride produces 4.45 g of fluorine and 1.25 g of sulfur, while decomposition of a sample of sulfur tetrafluoride produces 4.43 g of fluorine and 1.87 g of sulfur. Calculate the mass of fluorine per gram of sulfur for each sample and show that these results are consistent with the law of multiple proportions.

Which statements are consistent with Daltons atomic theory as it was originally stated? Why? a. Sulfur and oxygen atoms have the same mass. b. All cobalt atoms are identical. c. Potassium and chlorine atoms combine in a 1:1 ratio to form potassium chloride. d. Lead atoms can be converted into gold.

Which statements are inconsistent with Dalton’s atomic theory as it was originally stated? Why? a. All carbon atoms are identical. b. An oxygen atom combines with 1.5 hydrogen atoms to form a water molecule. c. Two oxygen atoms combine with a carbon atom to form a carbon dioxide molecule. d. The formation of a comp

Which statements are consistent with Rutherfords nuclear theory as it was originally stated? Why? a. The volume of an atom is mostly empty space. b. The nucleus of an atom is small compared to the size of the atom. c. Neutral lithium atoms contain more neutrons than protons. d. Neutral lithium atoms contain more protons than electrons.

Which statements are inconsistent with Rutherfords nuclear theory as it was originally stated? Why? a. Since electrons are smaller than protons, and since a hydrogen atom contains only 1 proton and 1 electron, it must follow that the volume of a hydrogen atom is mostly due to the proton. b. A nitrogen atom has 7 protons in its nucleus and 7 electrons outside of its nucleus. c. A phosphorus atom has 15 protons in its nucleus and 150 electrons outside of its nucleus. d. The majority of the mass of a fluorine atom is due to its 9 electrons.

A chemist in an imaginary universe, where electrons have a different charge than they do in our universe, performs the Millikan oil drop experiment to measure the electrons charge. The charges of several drops are recorded here. What is the charge of the electron in this imaginary universe?

Imagine a unit of charge called the zorg. A chemist performs the oil drop experiment and measures the charge of each drop in zorgs. Based on the results shown here, what is the charge of the electron in zorgs (z)? How many electrons are in each drop?

On a dry day, your body can accumulate static charge from walking across a carpet or from brushing your hair. If your body develops a charge of - 15 mC ( microcoulombs), how many excess electrons has it acquired? What is their collective mass?

How many electrons are necessary to produce a charge of -1.0 C? What is the mass of this many electrons?

Which statements about subatomic particles are true? a. If an atom has an equal number of protons and electrons, it will be charge-neutral. b. Electrons are attracted to protons. c. Electrons are much lighter than neutrons. d. Protons have twice the mass of neutrons.

Which statements about subatomic particles are false? a. Protons and electrons have charges of the same magnitude but opposite signs. b. Protons have about the same mass as neutrons. c. Some atoms dont have any protons. d. Protons and neutrons have charges of the same magnitude but opposite signs.

How many electrons would it take to equal the mass of a proton?

A helium nucleus has two protons and two neutrons. How many electrons would it take to equal the mass of a helium nucleus?

Write isotopic symbols in the form X- A (e.g., C-13) for each isotope. a. the silver isotope with 60 neutrons b. the silver isotope with 62 neutrons c. the uranium isotope with 146 neutrons d. the hydrogen isotope with 1 neutron

Write isotopic symbols in the form A ZX for each isotope. a. the copper isotope with 34 neutrons b. the copper isotope with 36 neutrons c. the potassium isotope with 21 neutrons d. the argon isotope with 22 neutrons

Determine the number of protons and the number of neutrons in each isotope. a. 14 7 N b. 23 11Na c. 222 86 Rn d. 208 82 Pb

Determine the number of protons and the number of neutrons in each isotope. a. 40 19K b. 226 88 Ra c. 99 43Tc d. 33 15P

The amount of carbon-14 in ancient artifacts and fossils is often used to establish their age. Determine the number of protons and the number of neutrons in a carbon-14 isotope and write its symbol in the form A ZX

Uranium-235 is used in nuclear fission. Determine the number of protons and the number of neutrons in uranium-235 and write its symbol in the form A ZX .

Determine the number of protons and the number of electrons in each ion. a. \(Ni^{2+}\) b. \(S^{2-}\) c. \(Br^-\) d. \(Cr^{3+}\)

Determine the number of protons and the number of electrons in each ion. a. Al3+ b. Se2- c. Ga3+ d. Sr2+

Predict the charge of the ion formed by each element. a. O b. K c. Al d. Rb

Predict the charge of the ion formed by each element. a. Mg b. N c. F d. Na

Fill in the blanks to complete the table.

Fill in the blanks to complete the table.

Write the name of each element and classify it as a metal, nonmetal, or metalloid. a. K b. Ba c. I d. O e. Sb

Write the symbol for each element and classify it as a metal, nonmetal, or metalloid. a. gold b. fl uorine c. sodium d. tin e. argon

Determine whether or not each element is a main-group element. a. tellurium b. potassium c. vanadium d. manganese

Determine whether or not each element is a transition element. a. Cr b. Br c. Mo d. Cs

Classify each element as an alkali metal, alkaline earth metal, halogen, or noble gas. a. sodium b. iodine c. calcium d. barium e. krypton

Classify each element as an alkali metal, alkaline earth metal, halogen, or noble gas. a. F b. Sr c. K d. Ne e. At

Which pair of elements do you expect to be most similar? Why? a. N and Ni b. Mo and Sn c. Na and Mg d. Cl and F e. Si and P

Which pair of elements do you expect to be most similar? Why? a. nitrogen and oxygen b. titanium and gallium c. lithium and sodium d. germanium and arsenic e. argon and bromine

Gallium has two naturally occurring isotopes with the following masses and natural abundances: Isotope Mass (amu) Abundance (%) Ga-69 68.92558 60.108 Ga-71 70.92470 39.892 Sketch the mass spectrum of Gallium.

Magnesium has three naturally occurring isotopes with the following masses and natural abundances: Isotope Mass (amu) Abundance (%) Mg-24 23.9850 78.99 Mg-25 24.9858 10.00 Mg-26 25.9826 11.01 Sketch the mass spectrum of magnesium.

The atomic mass of fluorine is 18.998 amu and its mass spectrum shows a large peak at this mass. The atomic mass of chlorine is 35.45 amu, yet the mass spectrum of chlorine does not show a peak at this mass. Explain the difference.

The atomic mass of copper is 63.546 amu. Do any copper isotopes have a mass of 63.546 amu? Explain.

An element has two naturally occurring isotopes. Isotope 1 has a mass of 120.9038 amu and a relative abundance of 57.4%, and isotope 2 has a mass of 122.9042 amu. Find the atomic mass of this element and identify it.

An element has four naturally occurring isotopes with the masses and natural abundances given here. Find the atomic mass of the element and identify it.

Bromine has two naturally occurring isotopes (Br-79 and Br-81) and has an atomic mass of 79.904 amu. The mass of Br-81 is 80.9163 amu, and its natural abundance is 49.31%. Calculate the mass and natural abundance of Br-79.

Use the mass spectrum of rubidium to determine the atomic mass of rubidium.

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

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

What is the mass, in grams, of each elemental sample? a. 2.3 * 10-3 mol Sb b. 0.0355 mol Ba c. 43.9 mol Xe d. 1.3 mol W

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

Calculate the number of atoms in each sample. a. 5.18 g P b. 2.26 g Hg c. 1.87 g Bi d. 0.082 g Sr

Use the mass spectrum of mercury to estimate the atomic mass of mercury. Estimate the masses and percent intensity values from the graph to three significant figures.

Nuclei with the same number of neutrons but different mass numbers are called isotones . Write the symbols of four isotones of 236 Th.

Carbon-12 contains six protons and six neutrons. The radius of the nucleus is approximately 2.7 fm (femtometers) and the radius of the atom is approximately 70 pm (picometers). Calculate the volume of the nucleus and the volume of the atom. What percentage of the carbon atoms volume is occupied by the nucleus? (Assume two significant figures.)

Consider the stack of pennies in the previous problem. How much money (in dollars) would this represent? If this money were equally distributed among the worlds population of 6.5 billion people, how much would each person receive? Would each person be a millionaire? Billionaire? Trillionaire?

The mass of an average blueberry is 0.75 g and the mass of an automobile is 2.0 * 103 kg . Find the number of automobiles whose total mass is the same as 1.0 mol of blueberries.

Suppose that atomic masses were based on the assignment of a mass of 12.000 g to 1 mol of carbon, rather than 1 mol of 12 C. What would the atomic mass of oxygen be? (The atomic masses of carbon and oxygen based on the assignment of 12.000 g to 1 mol of 12 C are 12.011 amu and 15.9994 amu, respectively.)

A pure titanium cube has an edge length of 2.78 in. How many titanium atoms does it contain? Titanium has a density of 4.50 g>cm3 .

A pure copper sphere has a radius of 0.935 in. How many copper atoms does it contain? [The volume of a sphere is (4>3)pr 3 and the density of copper is 8.96 g>cm3 .]

Boron has only two naturally occurring isotopes. The mass of boron-10 is 10.01294 amu and the mass of boron-11 is 11.00931 amu. Calculate the relative abundances of the two isotopes.

Lithium has only two naturally occurring isotopes. The mass of lithium-6 is 6.01512 amu and the mass of lithium-7 is 7.01601 amu. Calculate the relative abundances of the two isotopes.

Common brass is a copper and zinc alloy containing 37.0% zinc by mass and having a density of 8.48 g>cm 3 . A fitting composed of common brass has a total volume of 112.5 cm 3 . How many atoms (copper and zinc) does the fitting contain?

A 67.2 g sample of a gold and palladium alloy contains 2.49 * 1023 atoms. What is the composition (by mass) of the alloy?

Naturally occurring chlorine is composed of two isotopes: 75.76% Cl-35 (mass 34.9688 amu) and 24.24% Cl-37 (mass 36.9659 amu). Naturally occurring oxygen is composed of three isotopes: 99.757% O-16 (mass 15.9949 amu), 0.038% O-17 (mass 16.9991 amu), and 0.205% O-18 (mass 17.9991 amu). The compound dichlorine monoxide is composed of two chlorine atoms and one oxygen atom bonded together to form the Cl 2 O molecule. How many Cl 2 O molecules of different masses naturally exist? Give the masses of the three most abundant Cl 2 O molecules.

Silver is composed of two naturally occurring isotopes: Ag-107 (51.839%) and Ag-109. The ratio of the masses of the two isotopes is 1.0187. What is the mass of Ag-107?

The U.S. Environmental Protection Agency (EPA) sets limits on healthful levels of air pollutants. The maximum level that the EPA considers safe for lead air pollution is \(1.5 \mu \mathrm{g} / \mathrm{m}^3\). If your lungs were filled with air containing this level of lead, how many lead atoms would be in your lungs? (Assume a total lung volume of \(5.50 \mathrm{~L}\).)

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

In Section 2.9 , it was stated that 1 mol of sand grains would cover the state of Texas to several feet. Estimate how many feet by assuming that the sand grains are roughly cube-shaped, each one with an edge length of 0.10 mm. Texas has a land area of 268,601 square miles.

Use the concepts in this chapter to obtain an estimate for the number of atoms in the universe. Make the following assumptions: (a) All of the atoms in the universe are hydrogen atoms in stars. (This is not a ridiculous assumption because over three-fourths of the atoms in the universe are in fact hydrogen. Gas and dust between the stars represent only about 15% of the visible matter of our galaxy, and planets compose a far tinier fraction.) (b) The sun is a typical star composed of pure hydrogen with a density of \(1.4 \ g/cm^3\) and a radius of \(7 \times 10^8 \ m\). (c). Each of the roughly 100 billion stars in the Milky Way galaxy contains the same number of atoms as our sun. (d) Each of the 10 billion galaxies in the visible universe contains the same number of atoms as our Milky Way-galaxy.

On the previous page is a representation of 50 atoms of a fictitious element called westmontium (Wt). The red spheres represent Wt-296, the blue spheres Wt-297, and the green spheres Wt-298. a. Assuming that the sample is statistically representative of a naturally occurring sample, calculate the percent natural abundance of each Wt isotope. b. Draw the mass spectrum for a naturally occurring sample of Wt. c. The mass of each Wt isotope is measured relative to C-12 and tabulated next. Use the mass of C-12 to convert each of the masses to amu and calculate the atomic mass of Wt.

The ratio of oxygen to nitrogen by mass in NO 2 is 2.29. The ratio of fluorine to nitrogen by mass in NF 3 is 4.07. Find the ratio of oxygen to fluorine by mass in OF 2

Naturally occurring cobalt consists of only one isotope, 59 Co, whose relative atomic mass is 58.9332. A synthetic radioactive isotope of cobalt, 60 Co, has a relative atomic mass of 59.9338 and is used in radiation therapy for cancer. A 1.5886 g sample of cobalt has an apparent atomic mass of 58.9901. Find the mass of 60 Co in this sample.

A 7.36 g sample of copper is contaminated with an additional 0.51 g of zinc. Suppose an atomic mass measurement was performed on this sample. What would be the measured atomic mass?

The ratio of the mass of O to the mass of N in N 2 O 3 is 12:7. Another binary compound of nitrogen has a ratio of O to N of 16:7. What is its formula? What is the ratio of O to N in the next member of this series of compounds?

Naturally occurring magnesium has an atomic mass of 24.312 and consists of three isotopes. The major isotope is 24 Mg, natural abundance 78.99%, relative atomic mass 23.98504. The next most abundant isotope is 26 Mg, relative atomic mass 25.98259. The third most abundant isotope is 25 Mg, whose natural abundance is in the ratio of 0.9083 to that of 26 Mg. Find the relative atomic mass of 25 Mg

Which is an example of the law of multiple proportions? Explain. a. Two different samples of water are found to have the same ratio of hydrogen to oxygen. b. When hydrogen and oxygen react, the mass of water formed is exactly equal to the mass of hydrogen and oxygen that reacted. c. The mass ratio of oxygen to hydrogen in water is 8:1. The mass ratio of oxygen to hydrogen in hydrogen peroxide (a compound that only contains hydrogen and oxygen) is 16:1.

Lithium has two naturally occurring isotopes: Li-6 (natural abundance 7.5%) and Li-7 (natural abundance 92.5%). Using circles to represent protons and squares to represent neutrons, draw the nucleus of each isotope. How many Li-6 atoms would be present, on average, in a 1000-atom sample of lithium?

As we saw in the previous problem, lithium has two naturally occurring isotopes: Li-6 (natural abundance 7.5%; mass 6.0151 amu) and Li-7 (natural abundance 92.5%; mass 7.0160 amu). Without doing any calculations, determine which mass is closest to the atomic mass of Li. a. 6.00 amu b. 6.50 amu c. 7.00 amu

The mole is defined as the amount of a substance containing the same number of particles as exactly 12 grams of C-12. The amu is defined as 1/12 of the mass of an atom of C-12. Why is it important that both of these definitions reference the same isotope? What would be the result, for example, of defining the mole with respect to C-12, but the amu with respect to Ne-20?

Without doing any calculations, determine which of the samples contains the greatest amount of the element in moles. Which contains the greatest mass of the element? a. 55.0 g Cr b. 45.0 g Ti c. 60.0 g Zn

The atomic radii of the isotopes of an element are identical to one another. However, the atomic radii of the ions of an element are significantly different from the atomic radii of the neutral atom of the element. Explain.