Chapter 5

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5.5 The Mole5.6 Molar Mass

5.7 Mole Relationships in Chemical Equations

5.8 Mass Calculations for Reactions

Collection Terms

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1 trio = 3 singers

1 six-pack Cola = 6 cans Cola drink

1 dozen donuts = 12 donuts

1 gross of pencils = 144 pencils

A Moles of Particles

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Contains 6.02 x 1023 particles

1 mole C = 6.02 x 1023 C atoms

1 mole H2O = 6.02 x 1023 H2O

molecules

1 mole NaCl = 6.02 x 1023 Na+ ions and

6.02 x 1023 Cl– ions

Examples of Moles

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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

Avogadro’s Number

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6.02 x 1023 particles 1 mole

or

1 mole

6.02 x 1023 particles

Learning Check

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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 2) 4 3) 8

B. How many oranges in 2.0 meps?

1) 4 2) 8 3) 16

C. How many meps contain 40 gummy bears?

1) 5 2) 10 3) 20

Solution

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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

Learning Check

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1. Number of atoms in 0.500 mole of Al1) 500 Al atoms

2) 6.02 x 1023 Al atoms3) 3.01 x 1023 Al atoms

2.Number of moles of S in 1.8 x 1024 S atoms1) 1.0 mole S atoms2) 3.0 mole S atoms3) 1.1 x 1048 mole S atoms

Solution

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1. Number of atoms in 0.500 mol of Al3) 3.01 x 1023 Al atoms

0.500 mol Al x 6.02 x 1023 Al atoms1 mol Al

2. Number of moles of S if a sample of S contains 1.80 x 1024 S atoms2) 3.0 mole S atoms

1.80 x 1024 S atoms x 1 mol S

6.02 x 1023 S atoms

Molar Mass

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Number of grams in 1 mole Equal to the numerical value of the

atomic mass

1 mole of C atoms = 12.0 g

1 mole of Mg atoms = 24.3 g

1 mole of Cu atoms = 63.5 g

Learning Check

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Give the molar mass to 0.1 g

A. 1 mole of Br atoms =________

B. 1 mole of Sn atoms =________

Solution

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Give the molar mass to 0.1 g

A. 1 mole of Br atoms = 79.9 g/mole

B. 1 mole of Sn atoms = 118.7 g/mole

Molar Mass of Compounds

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Mass in grams of 1 mole equal numerically to the sum of the atomic masses

1 mole of CaCl2 = 111.1 g/mole

1 mole Ca x 40.1 g/mole

+ 2 moles Cl x 35.5 g/mole

1 mole of N2O4 = 74.0 g/mole2 moles N x 14.0 g/mole

+ 4 moles O x 16.0 g/mole

Learning Check

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A. 1 mole of K2O = ______g

B. 1 mole of antacid Al(OH)3 =

______g

Solution

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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

Learning Check

16

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

Solution

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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)

Learning Check

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What is the percent carbon in

C5H8NO4 (MSG monosodium

glutamate), a compound used to flavor foods and tenderize meats?1) 8.22 %C2) 24.3 %C3) 41.1 %C

Solution

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Molar mass = 146.0 g/mole% = total g C x 100

total g compound

= 60.0 g C x 100 = 41.1% C

146.0 g MSG

Molar Mass Factors

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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 and 1 mole

CH4

1 mole CH4 16.0 g CH4

Learning Check

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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 or g acetic acid

g acetic acid 1 mole acetic acid

Solution

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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 or 60.0 g acetic acid

60.0 g acetic acid 1 mole acetic acid

Calculations with Molar Mass

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molar mass Grams Moles

Moles and Grams

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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 1 mole Al =

27.0 g Al

2. Conversion factors for Al 27.0g Al or 1 mol Al

1 mol Al 27.0 g Al

3. Setup 3.00 moles Al x 27.0 g Al 1 mole Al

Answer = 81.0 g Al

Learning Check

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The artificial sweetener aspartame (Nutri-Sweet) formula

C14H18N2O5 is used to sweeten diet

foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame?

Solution

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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