Chapter 5
5.5 The Mole 5.6 Molar Mass 5.7 Mole Relationships in Chemical Equations 5.8 Mass Calculations for Reactions
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Collection Terms
1 trio
1 six-pack Cola
=
=
3 singers
6 cans Cola drink
1 dozen donuts
1 gross of pencils
=
=
12 donuts
144 pencils
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A Moles of Particles
Contains 6.02 x 1023 particles
1 mole C 1 mole H2O 1 mole NaCl = 6.02 x 1023 C atoms = 6.02 x 1023 H2O molecules = 6.02 x 1023 Na+ ions and 6.02 x 1023 Cl– ions
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Examples of Moles
Moles of elements 1 mole Mg = 6.02 x 1023 Mg atoms 1 mole Au = 6.02 x 1023 Au atoms Moles of compounds 1 mole NH3 = 6.02 x 1023 NH3 molecules 1 mole C9H8O4 = 6.02 x 1023 aspirin molecules
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Avogadro’s Number
6.02 x 1023 particles 1 mole or
1 mole
6.02 x 1023 particles
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Learning Check
Suppose we invented a new collection unit called a mep. One mep contains 8 objects.
A. How many paper clips in 1 mep?
1) 1 1) 4 2) 4 2) 8 3) 8 3) 16 B. How many oranges in 2.0 meps?
C. How many meps contain 40 gummy bears? 1) 5 2) 10 3) 20
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Solution
Suppose we invented a new collection unit called a mep. One mep contains 8 objects.
A. How many paper clips in 1 mep?
3) 8 B. How many oranges in 2.0 meps? 3) 16
C. How many meps contain 40 gummy bears? 1) 5
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Learning Check
1. Number of atoms in 0.500 mole of Al 1) 500 Al atoms 2) 6.02 x 1023 Al atoms 3) 3.01 x 1023 Al atoms
2.Number of moles of S in 1.8 x 1024 S atoms 1) 1.0 mole S atoms 2) 3.0 mole S atoms 3) 1.1 x 1048 mole S atoms
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Solution
1. Number of atoms in 0.500 mol of Al 3) 3.01 x 1023 Al atoms 0.500 mol Al x 6.02 x 1023 Al atoms 1 mol Al 2. Number of moles of S if a sample of S contains 4.50 x 1024 S atoms 2) 3.0 mole S atoms 4.50 x 1024 S atoms x 1 mol S 6.02 x 1023 S atoms 9
Molar Mass
Number of grams in 1 mole
Equal to the numerical value of the atomic mass 1 mole of C atoms 1 mole of Mg atoms 1 mole of Cu atoms = = = 12.0 g 24.3 g 63.5 g
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Learning Check
Give the molar mass to 0.1 g A. 1 mole of Br atoms = ________
B. 1 mole of Sn atoms
=
________
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Solution
Give the molar mass to 0.1 g A. 1 mole of Br atoms B. 1 mole of Sn atoms = = 79.9 g/mole 118.7 g/mole
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Molar Mass of Compounds
Mass in grams of 1 mole equal numerically to the sum of the atomic masses
1 mole of CaCl2 = 111.1 g/mole + 2 moles Cl x 35.5 g/mole
1 mole of N2O4 = 74.0 g/mole
1 mole Ca x 40.1 g/mole
2 moles N x 14.0 g/mole + 4 moles O x 16.0 g/mole
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Learning Check
A. 1 mole of K2O = ______g
B. 1 mole of antacid Al(OH)3
= ______g
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Solution
A. 1 mole of K2O = 94.2 g
2 K x 39.1 g/mole + 1 O x 16.0 g/mole
B. 1 mole of antacid Al(OH)3
= 78.0 g
1 Al x 27.0 g/mole + 3 O x 16.0 g/mole + 3 x 1.0
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Learning Check
Prozac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. It has a molar mass of
1) 40.0 g/mole 2) 262 g/mole
3) 309 g/mole
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Solution
Prozac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. It has a molar mass of 3) 309 g/mole 17C (12.0) + 18H (1.0) + 3F (19.0) + 1N (14.0) + 1 O (16.0)
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Learning Check
What is the percent carbon in C5H8NO4 (MSG monosodium glutamate), a compound used to flavor foods and tenderize meats? 1) 8.22 %C 2) 24.3 %C 3) 41.1 %C
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Solution
Molar mass = 146.0 g/mole % = total g C x 100 total g compound = 60.0 g C 146.0 g MSG x 100 = 41.1% C
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Molar Mass Factors
Methane CH4 known as natural gas is used in gas cook tops and gas heaters. Express the molar mass of methane in the form of conversion factors.
Molar mass of CH4 = 16.0 g 16.0 g CH4 1 mole CH4 and 1 mole CH4 16.0 g CH4
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Learning Check
Acetic acid CH3COOH is the acid in vinegar . It has a molar mass of 60.0 g/mole. 1 mole of acetic acid = ____________
1 mole acetic acid g acetic acid
or
g acetic acid 1 mole acetic acid
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Solution
Acetic acid CH3COOH is the acid in vinegar . It has a molar mass of 60.0 g/mole. 1 mole of acetic acid = 60.0 g acetic acid
1 mole acetic acid 60.0 g acetic acid
or
60.0 g acetic acid 1 mole acetic acid
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Calculations with Molar Mass
molar mass Grams Moles
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Moles and Grams
Aluminum is often used for the structure of light-weight bicycle frames. How many grams of Al are in 3.00 moles of Al?
3.00 moles Al ? g Al
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1. Molar mass of Al 2. Conversion factors for Al 27.0g Al 1 mol Al 3. Setup or
1 mole Al = 27.0 g Al
1 mol Al 27.0 g Al 27.0 g Al 1 mole Al = 81.0 g Al
3.00 moles Al x Answer
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Learning Check
The artificial sweetener aspartame (NutriSweet) formula C14H18N2O5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame?
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Solution
1. Molar mass of Aspartame C14H18N2O5 (14 x 12.0) + (18 x 1.01) + (2 x 14.0) + (5 x 16.0) = 294 g/mole
2. Setup
225 g aspartame x 1 mole aspartame 294 g aspartame
= 0.765 mole aspartame
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