The Mole and Stoichiometry REVIEW
True/False
Indicate whether the statement is true or false.
____
1.
The actual yield is always lower than the theoretical yield.
____
2.
The largest amount of starting material is always the excess reactant.
____
3.
Avogadro’s number refers to the number of particles in one gram of a substance.
____ 4.
One mole of a substance has the same number of particles as one mole of any other
substance, regardless of what substances are being compared.
____
5.
An element’s molar mass is equivalent to the atomic number of the element.
____
6.
If the atomic mass of a manganese atom is 54.94 amu, then its molar mass is 54.94 g/mol.
____ 7.
Stoichiometry is the study of the relationship between the amount of reactants used and the
amount of products made in a chemical reaction.
____ 8.
In a balanced chemical equation, the total number of moles of all the reactants is equal to
the total number of moles of all the products.
____ 9.
The stoichiometric relationship between any two substances in a reaction depends on the
mole ratio between those substances.
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
10.
Which conversion factor would best fit in the space labeled “B” in this diagram?
a. 1/Avogadro’s number
c. molar mass of substance
b. Avogadro’s number
d. 1/molar mass of substance
____
11.
Which element has a molar mass of 30.974 g/mol?
a. Potassium
c. Gallium
b. Phosphorus
d. Palladium
____
12.
Which is the correct molar mass for the compound FeSO4?
a. 103.85 g/mol
c. 415.4 g/mol
b. 151.85 g/mol
d. 247.85 g/mol
____
13.
a. Kelvin
What is the SI base unit used to measure the amount of a substance?
c. Meter
b. Kilogram
____
14.
Calculate the number of molecules in 4.0 mol H2O.
23
a.
24
b.
____
d. Mole
molecules
molecules
–23
d.
23
23
15.
24
a.
mol
1023 mol
b.
c.
molecules
molecules
atoms Ag?
c. 0.745 mol
d. 27.0 mol
____ 16.
Copper (Cu) is a transition element used in the making of coins. Calculate the mass in grams
of 0.0420 moles of copper.
a. 0.00697 g
c. 2.67 g
b. 0.252 g
d. 6.61 g
____
17.
How many moles of calcium are in 425 g calcium (Ca)?
a. 10.6 mol
c. 171 mol
b. 70.5 mol
d. 255 mol
____
18.
What is the mass of 2.25 moles of sulfuric acid (H2SO4)?
a. 50.0 g
c. 112 g
b. 98.0 g
d. 220 g
____
24
19.
atoms manganese (Mn)?
a.
101 g
c.
–1
b.
1
d.
1
g
g
g
____ 20.
Based on the mole ratios of the substances in a chemical reaction shown, which is the
correct equation for the chemical reaction?
Substances
Mole ratio
A:B
3:2
A:C
3:1
B:C
2:1
a.
c.
b.
d.
____
21.
Which is true of the reaction shown below?
a. The mole ratio of this reaction is 6:5:6.
b. Two molecules of Substance Y will be left over when this reaction goes to completion.
c. Substance Y is the limiting reagent in this reaction.
d. The addition of more molecules of Substance X will not affect the amount of Substance Z
that can be made.
____ 22.
Which conversion factor will correctly complete this setup for finding the number of moles
of O2 required to completely react with 75.0 grams of Sb? The balanced chemical equation for the reaction is
shown:
a. 1 mole/31.998 g O2
c. 3 moles O2/4 moles Sb
b. 4 moles Sb/3 moles O2
d. 31.998g O2 /1 mole
____
23.
Cu + 2 AgNO3
How many moles of Cu are needed to react with 5.8 moles of AgNO3?
3)2
+ 2 Ag
a. 2.9 moles
c. 5.8 moles
b. 3.8 moles
d. 11.6 moles
____ 24.
Hydrofluoric acid reacts with 31.3 g of silica to produce hexafluorosilicic acid. Determine the
percent yield of H2SiF6 if the actual yield is 60.3 g.
a. 0.818%
c. 31.8%
b. 12.2%
d. 81.8%
The Mole and Stoichiometry REVIEW
Answer Section
TRUE/FALSE
NAT:
NAT:
NAT:
1.
ANS:
T
PTS:
1
DIF:
Easy
REF:
Section 11.2
2.
ANS:
F
PTS:
1
DIF:
Easy
REF:
Section 11.3
3.
ANS:
F
PTS:
1
DIF:
Bloom's Level 1
B.2
STA:
ABC 11.2
4.
ANS:
T
1
DIF:
Bloom's Level 2
B.2
STA:
ABC 11.2
5.
ANS:
F
PTS:
1
DIF:
Bloom's Level 1
B.1 | B.2
STA:
ABC 11.2
6.
T
ANS:
PTS:
The molar mass of an element is numerically equal to its atomic mass.
PTS:
1
DIF:
1
OBJ:
11.2.1 Relate the mass of an atom to the mass of a mole of atoms.
NAT:
UCP.3 | B.1
TOP:
Relate the mass of an atom to the mass of a mole of atoms.
STA:
REF:
Page 313
ABC 11.2
KEY:
Molar mass
NOT:
The mass in grams of one mole of any pure substance is called its molar mass.
NAT:
NAT:
1
7.
ANS:
T
B.3
STA:
ABC 11.2
8.
ANS:
F
PTS:
PTS:
B.1 | B.2 | B.3
9.
NAT:
MSC:
ANS:
T
PTS:
B.1 | B.2 | B.3
1
DIF:
Bloom's Level 1
1
DIF:
Bloom's Level 2
STA:
ABC 11.2
1
DIF:
STA:
ABC 11.2
1
DIF:
Bloom's Level 2
1
DIF:
Bloom's Level 2
1
DIF:
Bloom's Level 3
Bloom's Level 2
MULTIPLE CHOICE
10.
NAT:
NAT:
NAT:
ANS:
C
PTS:
UCP.2 | B.2
STA:
ABC 11.2
11.
ANS:
B
PTS:
B.2
STA:
ABC 11.2
12.
ANS:
B
PTS:
UCP.3 | B.2
STA:
ABC 11.2
13.
D
ANS:
The mole is an SI base unit used to measure the amount of a substance.
Feedback
A
Kelvin is the SI unit of thermodynamic temperature.
B
Kilogram is the SI unit of mass.
C
Meter is the SI unit of length.
D
Correct!
PTS:
1
DIF:
1
REF:
Page 310
OBJ:
11.1.1 Describe how a mole is used in chemistry.
STA:
ABC 11.2
TOP:
KEY:
Mole
MSC:
1
14.
ANS:
B
NAT:
UCP.1 | UCP.3
Describe how a mole is used in chemistry.
Feedback
A
Multiply the number of moles by the number of molecules.
B
Correct!
C
Multiply the number of moles with the correct value of Avogadro's number.
D
The position of the decimal value is incorrect.
PTS:
1
DIF:
1
REF:
Page 311
OBJ: 11.1.3 Convert moles to number of representative particles and number of representative particles
to moles.
NAT: UCP.3 STA: ABC 11.2
TOP: Convert moles to number of representative particles and number of representative particles to
moles.
KEY:
Converting moles to representative particles
15.
ANS:
MSC:
3
C
Feedback
A
Multiply the number of atoms by the inverse of Avogadro's number.
B
After multiplying the number of atoms by the inverse of Avogadro's number, the
power of the indices is nullified.
C
Correct!
D
Divide the number of atoms by Avogadro's number.
PTS:
1
DIF:
1
REF:
Page 311
OBJ: 11.1.3 Convert moles to number of representative particles and number of representative particles
to moles.
NAT: UCP.3 STA: ABC 11.2
TOP: Convert moles to number of representative particles and number of representative particles to
moles.
KEY:
Converting representative particles to moles
16.
ANS:
C
MSC:
3
Feedback
A
Instead of dividing the known number of moles of copper by Avogadro's number,
multiply it with the molar mass of copper.
B
Instead of multiplying the known number of moles of copper by Avogadro's number,
multiply it with the molar mass of copper.
C
Correct!
D
Multiply the known number of moles of copper by the molar mass of copper.
PTS:
1
DIF:
1
REF:
Page 315
OBJ: 11.2.2 Calculate the number of moles in a given mass of an element and the mass of a given number
of moles of an element.
NAT: UCP.3 | B.1
STA: ABC 11.2
TOP: Calculate the number of moles in a given mass of an element and the mass of a given number of
moles of an element. KEY: Mole to mass conversion
MSC: 3
17.
ANS:
A
Feedback
A
Correct!
B
Instead of dividing 425 g of calcium by Avogadro's number, divide it by its molar mass.
C
Multiply the known amount of calcium by the inverse of its molar mass.
D
Instead of multiplying 425 g of calcium by Avogadro's number, divide it by its molar
mass.
PTS:
1
DIF:
1
REF:
Page 316
OBJ: 11.2.2 Calculate the number of moles in a given mass of an element and the mass of a given number
of moles of an element.
NAT: UCP.3 | B.1
STA: ABC 11.2
TOP: Calculate the number of moles in a given mass of an element and the mass of a given number of
moles of an element. KEY: Mass to mole conversion
MSC: 3
18.
ANS:
D
Step 1:
Step 2:
Feedback
A
The number of grams of sulfuric acid is 98.0 g.
B
Multiply the molar mass by 2.25 moles of sulfuric acid.
C
The atomic mass of oxygen is 16.
D
Correct!
PTS:
1
DIF:
2
REF:
Page 323
OBJ: 11.3.3 Calculate the number of moles of a compound from a given mass of the compound, and the
mass of a compound from a given number of moles of the compound.
NAT:
UCP.3 STA:
ABC 11.2
TOP: Calculate the number of moles of a compound from a given mass of the compound, and the mass of
a compound from a given number of moles of the compound.
KEY:
Converting moles of a compound to mass
19.
ANS:
MSC:
3
D
Feedback
A
Divide the number of atoms by Avogadro's number and then multiply it by the molar
mass of the element.
B
Multiply the calculated number of moles of the element by its molar mass.
C
Subtract 23 from the power of the element to obtain the correct power.
D
Correct!
PTS:
1
DIF:
2
REF:
Page 318
OBJ: 11.2.3 Calculate the number of moles of an element when given the number of atoms of the
element.
NAT:
UCP.3 | B.1
TOP:
Calculate the number of moles of an element when given the number of atoms of the element.
KEY:
Atoms to mass conversion
MSC:
3
20.
1
DIF:
Bloom's Level 2
DIF:
Bloom's Level 4
NAT:
ANS:
STA:
ABC 11.2
D
PTS:
UCP.2 | B.3
STA:
ABC 11.2
21.
B
PTS:
ANS:
1
NAT:
NAT:
NAT:
UCP.2 | B.3
STA:
ABC 11.2
22.
C
PTS:
UCP.2 | B.3
STA:
ABC 11.2
23.
A
PTS:
ANS:
ANS:
UCP.3 STA:
ABC 11.2
24.
D
ANS:
1
1
DIF:
Bloom's Level 4
DIF:
Bloom's Level 3
Percent yield
Feedback
A
Multiply the yield by 100 to calculate the percent yield.
B
Divide the actual yield by the theoretical yield.
C
The molar mass is incorrect.
D
Correct!
PTS:
1
DIF:
3
OBJ:
12.4.2 Determine the percent yield for a chemical reaction.
NAT:
UCP.3 | B.3
KEY:
Percent yield
STA:
REF:
Page 371
ABC 11.2
MSC:
TOP:
3
Determine the percent yield for a chemical reaction.