CHEM 110 (BEAMER)
PW45A
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PRACTICE WORK 45A: Molar Mass-02
Mass  Moles Calculations
General Information
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Do Date: W (4/25)
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Class Notes-53a. Reading: Chapter 8.3
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You might need your “naming covalent compounds” notes: Notes-33
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You might need your “naming ionic compounds” notes: Notes-43; and Polyatomic Ions Sheet: Appendix 8a.
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You will need your periodic table and your calculators for this assignment
Mass  Moles Calculations
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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.
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
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.
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CHEM 110 (BEAMER)
PW45A
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”).
4)
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)
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)
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CHEM 110 (BEAMER)
PW45A
6)
Calculate the number of moles of acetone, C 3H6O, 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.
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)
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.
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CHEM 110 (BEAMER)
PW45A
Answers
Answers in “blue” mean that the answer was corrected from an earlier version. The blue answer is correct.
1A)
811.54 g/mol Pb3(PO4)2
1B)
811.54 g Pb3(PO4)2 = 1 mol Pb3(PO4)2
1C)
29.0 g Pb3(PO4)2 OR 2.90 × 101 g Pb3(PO4)2
2 A)
342.30 g/mol C12H22O11
2B)
342.30 g C12H22O11 = 1 mol C12H22O11
2C)
0.50 g C12H22O11
3 A)
116.23 g/mol C7H16O
3B)
116.23 g C7H16O = 1 mol C7H16O
3C)
1.1903 kg C7H16O
4)
10. mol Cu2SO4 OR 1.0 × 101 mol Cu2SO4 (The answer must have two sigdigs).
5)
0.127 mol Au
6)
7.25 mol C3H6O
7)
51 mL C2H6O
8)
7.050 × 104 mol Cu
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