2.29 Which of the following drawings represents an Na
atom? ACa2ion? An Fion?
(a) (b) (c)
9+ 10− 11+ 11− 20+ 18−
2.30 Indicate where in the periodic table the following ele-ments are found:
(a) Elements that commonly form anions (b) Elements that commonly form cations (c) Elements that commonly form covalent bonds
2.31 In the following drawings, red spheres represent cations and blue spheres represent anions. Match each of the drawings (a)–(d) with the following ionic compounds:
(a) (b)
(c) FeCl2 (d) MgSO4
Li2CO3
Ca31PO422
(a) (b)
(c) (d)
Additional Problems
Atomic Theory
2.32 How does Dalton’s atomic theory account for the law of mass conservation and the law of definite propor-tions?
2.33 What is the law of multiple proportions, and how is it predicted by Dalton’s atomic theory?
2.34 Benzene, ethane, and ethylene are just three of a large number of hydrocarbons—compounds that contain only carbon and hydrogen. Show how the following data are consistent with the law of multiple propor-tions.
Mass of Carbon Mass of Hydrogen Compound in 5.00 g Sample in 5.00 g Sample
Benzene 4.61 g 0.39 g
Ethane 4.00 g 1.00 g
Ethylene 4.29 g 0.71 g
2.35 In addition to carbon monoxide (CO) and carbon diox-ide there is a third compound of carbon and oxygen called carbon suboxide. If a 2.500 g sample of car-bon suboxide contains 1.32 g of C and 1.18 g of O, show that the law of multiple proportions is followed.
1CO22,
2.36 The atomic mass of carbon (12.011 amu) is approxi-mately 12 times that of hydrogen (1.008 amu).
(a) Show how you can use this knowledge to calculate possible formulas for benzene, ethane, and ethyl-ene (Problem 2.34).
(b) Show how your answer to part (a) is consistent with the actual formulas for benzene
ethane and ethylene
2.37 What is a possible formula for carbon suboxide (Prob-lem 2.35)?
2.38 (a) If the average mass of a single hydrogen atom is what is the mass in grams of hydrogen atoms? How does your answer compare numerically with the atomic mass of hydrogen?
(b) If the average mass of a single oxygen atom is what is the mass in grams of oxygen atoms? How does your answer compare numerically with the atomic mass of oxygen?
2.39 (a) If the atomic mass of an element is x, what is the mass in grams of atoms of the element?
(See Problem 2.38.)
(b) If atoms of element Y have a mass of 83.80 g, what is the identity of Y?
6.02 * 1023
6.02 * 1023 6.02 * 1023
26.558 * 10-24 g, 6.02 * 1023 1.67 * 10-24 g,
1C2H42.
1C2H62, 1C6H62,
2.40 A binary compound of zinc and sulfur contains 67.1%
zinc by mass. What is the ratio of zinc and sulfur atoms in the compound?
2.41 There are two binary compounds of titanium and chlo-rine. One compound contains 31.04% titanium by mass, and the other contains 74.76% chlorine by mass. What are the ratios of titanium and chlorine atoms in the two compounds?
Elements and Atoms
2.42 What is the difference between an atom’s atomic num-ber and its mass numnum-ber?
2.43 What is the difference between an element’s atomic number and its atomic mass?
2.44 What is an isotope?
2.45 Carbon-14 and nitrogen-14 both have the same mass number, yet they are different elements. Explain.
2.46 The subscript giving the atomic number of an atom is often left off when writing an isotope symbol. For example, is often written simply as Why is this allowable?
2.47 Iodine has a lower atomic mass than tellurium (126.90 for iodine versus 127.60 for tellurium) even though it has a higher atomic number (53 for iodine versus 52 for tellurium). Explain.
2.48 Give names and symbols for the following elements:
(a) An element with atomic number 6 (b) An element with 18 protons in its nucleus (c) An element with 23 electrons
2.49 The radioactive isotope cesium-137 was produced in large amounts in fallout from the 1985 nuclear power-plant disaster at Chernobyl, Ukraine. Write the symbol for this isotope in standard format.
2.50 Write standard symbols for the following isotopes:
(a) Radon-220 (b) Polonium-210 (c) Gold-197
2.51 Write symbols for the following isotopes:
(a) and
(b) and
2.52 How many protons, neutrons, and electrons are in each of the following atoms?
(a) (b) (c) (d)
2.53 How many protons and neutrons are in the nucleus of the following atoms?
(a) (b) (c) (d)
2.54 Identify the following elements:
(a) (b) (c) (d)
2.55 Identify the following elements:
(a) 80202X (b) 78195X (c) 76184X (d) 83209X
74183X
46104X
2858X
1224X
207Pb
64Zn
32S
27Al
58142Ce
53131I
2760Co
715N
A = 60 Z = 27
A = 140 Z = 58
13C.
613C
2.56 Naturally occurring boron consists of two isotopes:
(19.9%) with an isotopic mass of 10.0129 amu and (80.1%) with an isotopic mass of 11.009 31 amu. What is the atomic mass of boron? Check your answer by look-ing at a periodic table.
2.57 Naturally occurring silver consists of two isotopes:
(51.84%) with an isotopic mass of 106.9051 amu and (48.16%) with an isotopic mass of 108.9048 amu. What is the atomic mass of silver? Check your answer in a periodic table.
2.58 Magnesium has three naturally occurring isotopes:
(23.985 amu) with 78.99% abundance, (24.986 amu) with 10.00% abundance, and a third with 11.01% abun-dance. Look up the atomic mass of magnesium, and then calculate the mass of the third isotope.
2.59 A sample of naturally occurring silicon consists of (27.9769 amu), (28.9765 amu), and (29.9738 amu). If the atomic mass of silicon is 28.0855 amu and the natural abundance of is 4.67%, what are the nat-ural abundances of and
Compounds and Mixtures, Molecules and Ions
2.60 Which of the following mixtures are homogeneous and which are heterogeneous?
(a) Muddy water (b) Concrete (c) House paint (d) A soft drink
2.61 Which of the following mixtures are homogeneous?
(a) 18 karat gold (b) Window glass (c) Tomato juice (d) Liquefied air
2.62 What is the difference between an atom and a mole-cule? Give an example of each.
2.63 What is the difference between a molecule and an ion?
Give an example of each.
2.64 What is the difference between a covalent bond and an ionic bond? Give an example of each.
2.65 Which of the following bonds are likely to be covalent and which ionic? Explain.
(a) (b) (c) (d)
2.66 The symbol CO stands for carbon monoxide, but the symbol Co stands for the element cobalt. Explain.
2.67 Correct the error in each of the following statements:
(a) The formula of ammonia is NH3.
(b) Molecules of potassium chloride have the formula KCl.
(c) is a cation.
(d) is a polyatomic ion.
2.68 How many protons and electrons are in each of the fol-lowing ions?
(a) (b) (c) (d)
2.69 What is the identity of the element X in the following ions?
(a) a cation that has 36 electrons (b) X,an anion that has 36 electrons
X2,
Au3
Se2
Rb Be2
CH4
Cl
O–Br Br–Cl
Na–Br B–Br
30Si?
28Si
29Si
30Si
29Si
28Si
25Mg
24Mg
109Ag
107Ag
11B
10B
Additional Problems 71 2.70 The structural formula of isopropyl alcohol, better
known as “rubbing alcohol,” is shown. What is the chemical formula of isopropyl alcohol?
2.71 Lactic acid, a compound found both in sour milk and in tired muscles, has the structure shown. What is its chemical formula?
2.72 Butane, the fuel used in disposable lighters, has the for-mula The carbon atoms are connected in the sequence and each carbon has a total of four covalent bonds. Draw a structural formula for butane.
2.73 Isooctane, the substance in gasoline from which the term octane rating derives, has the formula Each carbon has a total of four covalent bonds, and the atoms are connected in the sequence shown. Draw a complete structural formula for isooctane.
C8H18. C–C–C–C,
C4H10.
Acids and Bases
2.74 Which of the following compounds are acids and which are bases?
(a) HI (b) CsOH (c)
(d) (e)
2.75 For each of the acids you identified in Problem 2.74, tell how many ions can be donated from one molecule of acid.
2.76 Identify the anion that results when each of the acids in Problem 2.74 dissolves in water.
2.77 Identify the cation that results when each of the bases in Problem 2.74 dissolves in water.
H
H2CO3
Ba1OH22
H3PO4
Naming Compounds
2.78 Write formulas for the following binary compounds:
(a) Potassium chloride (b) Tin(II) bromide (c) Calcium oxide (d) Barium chloride (e) Aluminum hydride
2.79 Write formulas for the following compounds:
(a) Calcium acetate (b) Iron(II) cyanide (c) Sodium dichromate (d) Chromium(III) sulfate (e) Mercury(II) perchlorate 2.80 Name the following ions:
(a) (b) (c) (d)
(e) (f) (g) (h)
(i) (j)
2.81 Name the following binary molecular compounds:
(a) (b) (c) (d)
2.82 Give the formulas and charges of the following ions:
(a) Sulfite ion (b) Phosphate ion (c) Zirconium(IV) ion (d) Chromate ion (e) Acetate ion (f) Thiosulfate ion 2.83 What are the charges on the positive ions in the
follow-ing compounds?
(a) (b) (c)
(d) (e) (f)
(g) (h)
2.84 Name each of the compounds in Problem 2.83.
2.85 Name each of the following compounds:
(a) (b) (c)
(d) (e) (f)
(g) (h)
2.86 Fill in the missing information to give formulas for the following compounds:
(a) (b) (c)
2.87 Write formulas for each of the following compounds:
(a) Sodium peroxide (b) Aluminum bromide (c) Chromium(III) sulfate
Ga?1SO42?
Ba?1PO42?
Na?SO4
LiClO3
Al21SO423
KMnO4
BaSO4
ZnCrO4
Mn1HCO322
Co1NO222
MgSO3
Cu1CH3CO222
KIO4
MnO2
Hg2S Sn31PO422
Ti1SO422
Fe1NO223
Zn1CN22
N2O3
N2O ClO2
CCl4
ClO4
Mn2
ClO2
NO2
Ni2
NH4
HCO3
V3
Cs Ba2
O H
H C C C
H H
H Isopropyl alcohol H
H
H
O H
H C C C
H H
O Lactic acid O
H H
C
C C C C
C
C C