Instructor’s Manual to Accompany Cracolice/Peters 3/e
8.  a) NF3: 14.01 + 3(19.00) = 71.01 amu
b) BaCl2: 137.3 + 2(35.45) = 208.2 amu
c) Pb3(PO4)2: 3(207.2) + 2(30.97) + 8(16.00) = 811.5 amu
10. The mole is the amount of any substance that contains the same number of units as the number of atoms
in exactly 12 grams of carbon-12. It is convenient to think of the mole as a number: 6.02 × 1023. The mole
is used to count the huge number of atoms and molecules in macroscopic samples.
12. Avogadro’s number, 6.02 × 1023
14.  a) 1.25 mol ×
6.02 " 10 23 molecules
= 7.53 × 1023 molecules
mol
1 mol
b) 7.04 × 1022 molecules ×
= 0.117 mol
23
6.02
"
10
molecules
!
1 mol
c) 7.89 × 1022 molecules ×
= 0.131 mol
23
6.02
"
10
molecules
!
d) 1.60 mol ×
6.02 " 10 23 molecules
= 9.63 × 1023 molecules
mol
!
2 mol H
6.02 " 10 23 H atoms
16.  a) 2.69 mol H2O ×
×
= 3.24 × 1024 H atoms
1
mol
H
O
mol
H
2
!
1 mol H 2O
1 mol O
b) 1.39 × 1022 molecules H2O ×
×
= 0.0231 mol O
23
! 6.02 " 10 molecules H 2O 1 mol H 2O
!
18. Molar mass is the mass of one mole of molecules or formula units, expressed in grams per mole.
! in amu.
Molecular mass is the !
mass of a single molecule, expressed
20.  a) CrI2: 52.00 + 2(126.9) = 305.8 g/mol
b) SiO2: 28.09 + 2(16.00) = 60.09 g/mol
c) CF4: 12.01 + 4(19.00) = 88.01 g/mol
22. a) 53.8 g Be ×
1 mol Be
= 5.97 mol Be
9.012 g Be
1 mol C 3 H 4 Cl4
b) 781 g C3H4Cl4 ×
= 4.29 mol C3H4Cl4
181.86 g C 3 H 4 Cl4
!
1 mol Ca(OH) 2
c) 0.756 g Ca(OH)2 ×
= 0.0102 mol Ca(OH)2
74.10 g Ca(OH) 2
!
1 mol CoBr3
d) 9.94 g CoBr3 ×
= 0.0333 mol CoBr3
298.63 g CoBr3
!
18
!
Instructor’s Manual to Accompany Cracolice/Peters 3/e
1 mol (NH 4 ) 2 Cr2O 7
= 0.0349 mol (NH4)2Cr2O7
252.08 g (NH 4 ) 2 Cr2O 7
e) 8.80 g (NH4)2Cr2O7 ×
1 mol Mg(ClO 4 ) 2
f) 28.3 g Mg(ClO4)2 ×
= 0.127 mol Mg(ClO4)2
223.32 g Mg(ClO 4 ) 2
!
1 mol NaClO
24. a) 91.9 g ×
= 1.23 mol NaClO
74.44 g NaClO
!
1 mol Al(C 2 H 3O 2 ) 3
b) 881 g Al(C2H3O2)3 ×
= 4.32 mol Al(C2H3O2)3
204.11 g Al(C 2 H 3O 2 ) 3
!
1 mol Hg 2Cl2
c) 0.586 g Hg2Cl2 ×
= 0.00124 mol Hg2Cl2
472.1 g Hg 2Cl2
!
26. a) 0.542 mol NaHCO3 ×
!
84.01 g NaHCO 3
= 45.5 g NaHCO3
mol NaHCO 3
b) 0.0789 mol AgNO3 ×
!
169.9 g AgNO 3
= 13.4 g AgNO3
mol AgNO 3
c) 9.61 mol Na2HPO4 ×
!
141.96 g Na 2 HPO 4
= 1.36 × 103 g Na2HPO4
mol Na 2 HPO 4
d) 0.903 mol Ca(BrO3)2 ×
!
295.88 g Ca(BrO 3 ) 2
= 267 g Ca(BrO3)2
mol Ca(BrO 3 ) 2
e) 1.14 mol (NH4)2SO3 ×
!
116.15 g (NH 4 ) 2 SO 3
= 132 g (NH4)2SO3
mol (NH 4 ) 2 SO 3
28. a) 0.819 mol MnO2 ×
!
86.94 g MnO 2
= 71.2 g MnO2
mol MnO 2
b) 8.48 mol Al(ClO3)3 ×
!
c) 0.926 mol CrCl2 ×
!
277.33 g Al(ClO 3 ) 3
= 2.35 × 103 g Al(ClO3)3
mol Al(ClO 3 ) 3
122.90 g CrCl2
= 114 g CrCl2
mol CrCl2
1 mol Be(NO 3 ) 2
6.02 " 10 23 Be(NO 3 ) 2 units
30. a) 85.5 g Be(NO3)2 ×
×
=
133.03 g Be(NO 3 ) 2
mol Be(NO 3 ) 2
!
3.87 × 1023 Be(NO3)2 units
b) 9.42 g Mn ×
!
!
!
1 mol Mn
6.02 " 10 23 Mn atoms
×
= 1.03 × 1023 Mn atoms
54.94 g Mn
mol Mn
!
19