1. Chapter 7 Chemical Quantities
7.3 Calculations Using Molar Mass
Learning Goal Given the number of moles of a substance, calculate the mass in grams; given the mass, calculate the number of moles.
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2. is a useful conversion factor converts moles of a substance to grams
Using Molar Mass
The molar mass
is a useful conversion factor
converts moles of a substance to grams
converts mass in grams of a substance to moles
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3. Guide to Calculating Moles from Grams or Grams from Moles
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4. Silver metal is used in the manufacture of
Learning Check
Silver metal is used in the manufacture of
tableware, mirrors, dental alloys, and jewelry.
If the design for a piece of jewelry requires
0.750 mole of silver, how many grams of silver
are needed?
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5. If the design for a piece of jewelry requires
Solution
If the design for a piece of jewelry requires
0.750 mole of silver, how many grams of silver
are needed?
Step 1 State the given and needed quantities.
Given: mole of Ag
Need: grams of Ag
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6. If the design for a piece of jewelry requires
Solution
If the design for a piece of jewelry requires
0.750 mole of silver, how many grams of silver
are needed?
Step 2 Write a plan to convert moles to grams.
0.750 mol of Ag grams of Ag
Molar Mass
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7. If the design for a piece of jewelry requires
Solution
If the design for a piece of jewelry requires
0.750 mole of silver, how many grams of silver
are needed?
Step 3 Determine the molar mass and write conversion factors.
© 2014 Pearson Education, Inc.

8. If the design for a piece of jewelry requires
Solution
If the design for a piece of jewelry requires
0.750 mole of silver, how many grams of silver
are needed?
Step 4 Set up the problem to convert moles to grams (or grams to moles).
© 2014 Pearson Education, Inc.

9. Conversion Factors for Compounds
Conversion factors are written for compounds in
the same way as those written for elements.
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10. A box of salt contains 737 g of NaCl. How many
Learning Check
A box of salt contains 737 g of NaCl. How many
moles of NaCl are present in the box?
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11. A box of salt contains 737 g of NaCl. How many
Solution
A box of salt contains 737 g of NaCl. How many
moles of NaCl are present in the box?
Step 1 State the given and needed quantities.
Given: 737 g NaCl
Need: moles of NaCl
© 2014 Pearson Education, Inc.

12. A box of salt contains 737 g of NaCl. How many
Solution
A box of salt contains 737 g of NaCl. How many
moles of NaCl are present in the box?
Step 2 Write a plan to convert grams to moles.
grams of NaCl moles of NaCl
Molar Mass
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13. A box of salt contains 737 g of NaCl. How many
Solution
A box of salt contains 737 g of NaCl. How many
moles of NaCl are present in the box?
Step 3 Determine the molar mass and write conversion factors.
(1 × 22.99) + 1(35.45) = g/mol
© 2014 Pearson Education, Inc.

14. A box of salt contains 737 g of NaCl. How many
Solution
A box of salt contains 737 g of NaCl. How many
moles of NaCl are present in the box?
Step 4 Set up the problem to convert grams to moles.
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15. Summary of Conversions
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16. Converting Mass to Molecules
Moles of
element or
compound
Molar Mass
g/mol
Avogadro’s
Number
Grams of
element or
compound
Atoms of element or
molecules of compound
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17. Guide to Calculating Particles from Mass
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18. A 10.00-lb bag of table sugar contains 4536 g of
Learning Check
A lb bag of table sugar contains 4536 g of
sucrose, C12H22O11. How many molecules of
sucrose are present?
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19. A 10.00-lb bag of table sugar contains 4536 g of
Solution
A lb bag of table sugar contains 4536 g of
sucrose, C12H22O11. How many molecules of
sucrose are present?
Step 1 State the given and needed quantities.
Given: g sucrose, C12H22O11
Need: molecules of sucrose
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20. A 10.00-lb bag of table sugar contains 4536 g of
Solution
A lb bag of table sugar contains 4536 g of
sucrose, C12H22O11. How many molecules of
sucrose are present?
Step 2 Write a plan to convert grams to particles.
Molar Mass
Avogadro’s Number
molecules of
sucrose
grams of
sucrose
moles of
sucrose
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21. A 10.00-lb bag of table sugar contains 4536 g of
Solution
A lb bag of table sugar contains 4536 g of
sucrose, C12H22O11. How many molecules of
sucrose are present?
Step 3 Write the equalities and conversion factors.
© 2014 Pearson Education, Inc.

22. A 10.00-lb bag of table sugar contains 4536 g of
Solution
A lb bag of table sugar contains 4536 g of
sucrose, C12H22O11. How many molecules of
sucrose are present?
Step 4 Set up the problem to convert grams
to particles.
© 2014 Pearson Education, Inc.