1 chapter 7 chemical quantities 7.3 calculations using molar mass basic chemistry copyright © 2011...
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Chapter 7 Chemical Quantities
7.3 Calculations Using Molar Mass
Basic Chemistry Copyright © 2011 Pearson Education, Inc.
Table salt is NaCl.
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Molar mass conversion factors • are written from molar mass• relate grams and moles of an element or
compound
Example: Write molar mass factors for methane CH4
used in gas cook tops and gas heaters.
Molar mass:
1 mol CH4 = 16.04 g
Conversion factors:
16.04 g CH4 and 1 mol CH4
1 mol CH4 16.04 g CH4
Molar Mass Factors
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Acetic acid HC2H3O2 gives the sour taste to vinegar. Write an equality and two molar mass conversion factors for acetic acid.
Learning Check
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Acetic acid HC2H3O2 gives the sour taste to vinegar.Write an equality and two molar mass conversion
factors for acetic acid.
Equality:
1 mol of acetic acid = 60.05 g of acetic acid
Molar mass conversion factors:
1 mol acetic acid and 60.05 g acetic acid 60.05 g acetic acid 1 mol acetic acid
Solution
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Aluminum is used to build lightweight bicycleframes. How many grams of Al are in 3.00 mol of Al?
Moles to Grams
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STEP 1 Given 3.00 mol of Al Need grams of Al
STEP 2 Plan moles of Al grams of Al
STEP 3 Equalities/Conversion Factors
1 mol of Al = 26.98 g of Al 1 mol Al and 26.98 g Al
26.98 g Al 1 mol Al
Solution
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STEP 4 Set Up ProblemSet up with molar mass as a factor:
3.00 mol Al x 26.98 g Al = 80.9 g of Al 1 mol Al molar mass factor for Al
Solution (continued)
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The artificial sweetener aspartame (NutraSweet), C14H18N2O5, is used to sweeten diet foods, coffee, and soft drinks. How many moles of aspartame are present in 225 g of aspartame?
Learning Check
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STEP 1 Given 225 g of C14H18N2O5 Need molesSTEP 2 Plan g of aspartame moles of aspartameSTEP 3 Equalities/Conversion Factors
1 mol aspartame = 294.3 g 1 mol aspartame and 294.3 g aspartame 294.3 g aspartame 1 mol aspartameSTEP 4 Set Up Problem
225 g aspartame x 1 mol aspartame 294.3 g aspartame
mole factor (inverted)
= 0.765 mol of aspartame
Solution
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Learning CheckAllyl sulfide, C6H10S, is a compound that has the odor of garlic. How many moles of C6H10S are in 225 g of C6H10S?
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STEP 1 Given 225 g of C6H10S Need moles of C6H10S
STEP 2 Plan g of C6H10S moles of C6H10S
STEP 3 Equalities/Conversion Factors
1 mol of C6H10S = 114.21 g of C6H10S
1 mol C6H10S and 114.21 g C6H10S
114.21 g C6H10S 1 mol C6H10S
STEP 3 Set Up Problem 225 g C6H10S x 1 mol C6H10S
114.21 g C6H10S
= 1.97 mol C6H10S
Solution
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Learning Check
How many molecules of H2O are in 24.0 g of H2O?
1) 4.52 x 1023
2) 1.44 x 1025
3) 8.02 x 1023
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Solution
STEP 1 Given 24.0 g of H2O
Need molecules of H2O
STEP 2 Plan
g of H2O moles of H2O molecules of H2O
STEP 3 Equalities/Conversion Factors
1 mol of H2O = 18.02 g of H2O
1 mol H2O and 18.02 g H2O
18.02 g H2O 1 mol H2O
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Solution (continued)
STEP 3 Equalities/Conversion Factors (continued)
1 mol of H2O = 6.022 molecules of H2O
1 mol H2O and 6.022 x 1023 H2O molecules
6.022 H2O molecules 1 mol H2O
STEP 4 Set Up Problem
24.0 g H2O x 1 mol H2O
18.02 g H2O
x 6.022 x 1023 H2O molecules
1 mol H2O
= 8.02 x 1023 H2O molecules (3)
Basic Chemistry Copyright © 2011 Pearson Education, Inc.