12) 26 g of aluminum have the same number of atoms as 26 g of iron.
13) 18 g of water have the same number of atoms as 48 g of ozone.
14) One mole of hydrogen gas has 6.02 x 1023 atoms
15) One mole of ozone, O3, has 1.8 x 1024 atoms.
16) There are more atoms in one formula unit of Na3PO4 than in one molecule of HCl.
17) There are more atoms in 20 g Na3PO4 than in 20 g HCl.
18) 21.2 g KBr is equal to 0.178 moles of KBr.
19) The mass of two moles of potassium dichromate is 294.2 g.
20) When 10 moles of hydrogen and 10 moles of oxygen are mixed to produce water, the
limiting reagent is hydrogen.
21) The molecular formula is the simplest formula using whole numbers.
22) The empirical formula is never equal to the molecular formula.
23) Acetic acid, C2H4O2, and glucose, C6H12O6, have the same empirical formula.
24) Formaldehyde, CH2O, and glucose, C6H12O6, have the same empirical formula, which
happens to be equal to the molecular formula of formaldehyde.
25) The percent composition of chlorine in C6H8NCl is 23.4%.
26) The empirical formula of laughing gas that contains 63.6% N and 36.4% O is N2O.
27) The percent composition of carbon is equal to the percent composition of oxygen in carbon
monoxide, CO.
28) The percent composition of sulfur is approximately equal to the percent composition of
oxygen in sulfur dioxide, SO2.
29) The percent of nitrogen in ferric nitrate is 17.4%.
30) A lead-sulfur compound contains 86.6% Pb. Its empirical formula is PbS2.
31) The molecular formula for a compound with an empirical formula of CH2O and a molar
mass of 120, is C3H6O3.
32) The percent of aluminum in bauxite (also known as aluminum oxide) is 52.9%.
1) Determine the number of grams of copper present in a 4.0 kg sample of the mineral
chalcopyrite (CuFeS2).
2) Determine the amount of carbon (in grams) present in 0.525 grams of benzoic acid (C7H6O2).
3) Determine the amount of oxygen present (in grams) in 1.00 grams of the artificial sweetener
aspartame (C14H18N2O5).
4) What is the theoretical yield in grams of K3[Fe(C2O4)3], if 5.700 grams of FeCl3 is used, and
K2C2O4 is present in excess?
FeC13 + 3K2C2O4 → K3[Fe(C2O4)3] + 3KCl
5) What is the theoretical yield in grams of BaSO4, if 0.6200 mol Na2SO4 and 0.7000 mol
BaCl2 are mixed?
Na2SO4+ BaC12 → BaSO4 + 2NaCl
6) Determine the molecular formula for a compound that weighs 44.1 g/mol and is 81.7% C and
18.3% H by mass.
7) Determine the molecular formula for a compound that weighs 176.13 g/mol and is 40.9% C,
54.5% O, and 4.6% H by mass.
8) Determine the molecular formula for a compound that has a molar mass of 157.01 g/mol and
is 45.9% C, 50.9% Br, and 3.21% H by mass.
9) Determine the molecular formula for a compound that has a molar mass of 135 g/mol and is
44.4% C, 51.9% N, and 3.7% H by mass.
9.4 Matching Questions
Match each compound in the left column with the corresponding number of atoms per formula
unit in the right column.
A) 19
B) 23
C) 22
D) 13
E) 17
1) (NH4)3PO3
Section: Section 9.2
Learning Outcome: 9.1 Describe what a mole is and how it relates to formulas of substances,
molar mass, and chemical equations.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
2) Al2(SO4)3
Section: Section 9.2
Learning Outcome: 9.1 Describe what a mole is and how it relates to formulas of substances,
molar mass, and chemical equations.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
3) Ca3(PO4)2
Section: Section 9.2
Learning Outcome: 9.1 Describe what a mole is and how it relates to formulas of substances,
molar mass, and chemical equations.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
4) K4Fe(CNO)6
Section: Section 9.2
Learning Outcome: 9.1 Describe what a mole is and how it relates to formulas of substances,
molar mass, and chemical equations.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
5) Al (C2H3O2)3
Section: Section 9.2
Learning Outcome: 9.1 Describe what a mole is and how it relates to formulas of substances,
molar mass, and chemical equations.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
Match each compound in the left column with its corresponding molecular mass in the right
column.
A) 342
B) 310
C) 88
D) 122.5
6) Ca3(PO4)2
Section: Section 9.2
Learning Outcome: 9.1 Describe what a mole is and how it relates to formulas of substances,
molar mass, and chemical equations.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
7) C4H8O2
Section: Section 9.2
Learning Outcome: 9.1 Describe what a mole is and how it relates to formulas of substances,
molar mass, and chemical equations.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
8) Al2(SO4)3
Section: Section 9.2
Learning Outcome: 9.1 Describe what a mole is and how it relates to formulas of substances,
molar mass, and chemical equations.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
9) KClO3
Section: Section 9.2
Learning Outcome: 9.1 Describe what a mole is and how it relates to formulas of substances,
molar mass, and chemical equations.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
Match each compound in the left column with the corresponding percent of nitrogen that
appears in the right column.
A) 29.2%
B) 63.6%
C) 7.7%
D) 30.4%
10) N2O
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
11) NO2
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
12) (NH4)2CO3
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
13) C18H26N2O4S
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
14) Ca(CN)2
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
Match each compound in the left column with the corresponding percent of sulfur that appears
in the right column.
A) 8.7%
B) 22.6%
C) 41.1%
D) 40.6%
15) Na2S
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
16) Na2SO4
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
17) Na2S2O3
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
18) C18H26N2O4S
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
Match each compound in the left column with the corresponding percent of carbon that appears
in the right column.
A) 48.6%
B) 55.6%
C) 69.0%
D) 33.6%
E) 41.8%
19) C6H8ClN
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
20) C3H10N2
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
21) C4H8Cl2O
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
22) C6H8N2O2S
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
23) C10H6O3
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
Match each compound in the left column with the corresponding percent of oxygen that appears
in the right column.
A) 50.0%
B) 26.1%
C) 43.8%
D) 18.6%
E) 27.6%
24) C2H3NO2
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
25) (NH4)2CO3
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
26) C10H6O3
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
27) C6H8N2O2S
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.
28) C10H16O3
Section: Section 9.6
Learning Outcome: 9.5 Calculate % by mass elemental compositions from a molecular formula.
Global Obj: G4 Demonstrate the quantitative skills needed to succeed in chemistry.