CHEM 110 (BEAMER)
SOLUTIONS SET
PW45B
Last Name
Do Date
First Name
Section
M
T
W
R
PRACTICE WORK 45B: Molar Mass-02
Mass  Moles Calculations
General Information

Do Date: W (4/25)

Class Notes-53a. Reading: Chapter 8.3

You might need your “naming covalent compounds” notes: Notes-33

You might need your “naming ionic compounds” notes: Notes-43; and Polyatomic Ions Sheet: Appendix 8a.

You will need your periodic table and your calculators for this assignment
Mass  Moles Calculations

Show your work – including units – through every step. You do not need to include representative particles.

You do not need to show your work for calculating molar mass values.
Pb3(PO4)2 : 811.54 g/mol
1A)
Calculate the molar mass of lead(II) phosphate.
1B)
Write your answer to Question 1A as a conversion factor:
1C)
Calculate the mass (in grams) of Pb3(PO4)2 in a 0.0357-mole sample of Pb3(PO4)2
(
811.54 g Pb3(PO4)2 = 1 mol Pb3(PO4)2
0.0357 mol Pb3 (PO4 )2
811.54 g Pb3 (PO4 )2
1
) (
) = x29.0 g Pb3 (PO4 )2 OR 2.90 × 10 g Pb3 (PO4 )2 x
(1)
1 mol Pb3 (PO4 )2
C12H22O11 : 342.30 g/mol
2A)
Calculate the molar mass of sucrose: C 12H22O11.
2B)
Write your answer to Question 2A as a conversion factor:
2C)
Calculate the number of moles of sucrose, C12H22O11, in a 170-gram sample of C12H22O11.
(
342.30 g C12H22O11 = 1 mol C12H22O12
170 g C12 H22 O11
1 mol C12 H22 O11
) (
) = x0.50 g C12 H22 O11 x
(1)
342.30. g C12 H22 O11
Page 1 of 3
CHEM 110 (BEAMER)
SOLUTIONS SET
PW45B
116.23 g/mol C7H16O
3A)
Calculate the molar mass of n-hexanol, C7H16O.
3B)
Write your answer to Question 3A as a conversion factor:
3C)
Calculate the mass (in kilograms) of a 10.241-mol sample of n-heptanol. In your work, you must show the
conversion of grams to kilograms. (You can’t just “slap the decimal point around”).
(
116.23 g C7H16O = 1 mol C7H16O
10.241 mol C7 H16 O
116.23 g C7 H16 O
1 kg C7 H16 O
) (
) (
)=
(1)
1 mol C7 H16 O
1000 g C7 H16 O
x1.1903 kg C7 H16 Ox
Remember: you can always choose to break the calculations into parts. For example:
4)

(
10.241 mol C7 H16 O
116.23 g C7 H16 O
) (
) = 1190.31 g C7 H16 O
(1)
1 mol C7 H16 O

(
1190.31 g C7 H16 O
1 kg C7 H16 O
) (
)=
(1)
1000 g C7 H16 O
Calculate the number of moles of copper(I) sulfate in a 5.0-pound sample of copper(I) sulfate.
Note: 1 lb = 453.59 g.
(
5)
x1.1903 kg C7 H16 Ox
5.0 lb Cu2 SO4
453.59 g Cu2 SO4
1 mol Cu2 SO4
) (
)(
) =
(1)
1 lb Cu2 SO4
223.17 g Cu2 SO4
x10. mol Cu2 SO4 x
Calculate the number of moles of gold in a 12.5-carat sample of gold.
Note: there are 5 carats in 1 gram. (5 c = 1 g)
(
12.5 c Au
5 g Au
1 mol Au
) (
)(
) =
(1)
1 c Au
197.0 g Au
x0.127 mol Aux
Page 2 of 3
CHEM 110 (BEAMER)
6)
SOLUTIONS SET
PW45B
Calculate the number of moles of acetone, C3H6O, in a 4.21-μg sample of acetone. In your work, you must show
the conversion of micrograms to grams. Remember that you are still expected to know the metric prefixes that
you memorized at the beginning of the semester! You don’t have to show your work for calculating molar mass.
‒6
4.21 μg C3 H6 O
1 × 10 g C3 H6 O
1 mol C3 H6 O
(
) (
) (
)=
(1)
1 μg C3 H6 O
58.09 g C3 H6 O
x7.25 × 10
‒8
mol C3 H6 Ox
Note: The answer has been corrected from a previous version.
7)
A sample of liquid contains 0.88 moles of ethanol, C2H6O. The density of this substance is 0.789 g/mL. Calculate
the volume (in mL) of ethanol. Remember that you are still required to know how to use density as a conversion
factor. You do not need to show work for calculating molar mass.
(
8)
0.88 mol C2 H6 O
46.07 g C2 H6 O
1 mL C2 H6 O
) (
) (
)=
(1)
1 mol C2 H6 O
0.789 g C2 H6 O
x51 mL C2 H6 Ox
Calculate the number of moles of silver are in 0.5000 cubic meters of copper. You must show the conversion
factor between meters and cubic meters in your work. (On a test, you will have to derive this.) The density of
copper is 8.96 g/cm3.

100 cm = 1 m
Remember: 1 L = 1 dm3

(100 cm)3 = (1 m)3
Remember: 1 mL = 1 cm3

1 × 106 cm3 = 1 m3
6
(
0.5000 m3 Cu
1 × 10 cm3 Cu
8.96 g Cu
1 mol Cu
) (
) (
) (
)=
3
3
(1)
63.55 g Cu
1 m Cu
1 cm Cu
4
x7.050 × 10 mol Cux
\
Page 3 of 3