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Chapter 3

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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

Collection Terms

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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

A Moles of Particles

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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

Examples of Moles

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6.02 x 1023 particles

1 mole

or

1 mole

6.02 x 1023 particles

Avogadro’s Number

The Mole and Molar

The mole is defined as the amount of a substance that contains as many elementary entities as there are atoms in exactly 12 g of carbon-12.

The experimentally determined number is called Avogadro’s number (NA)

NA = 6.0221415 x 1023

The Mole and Molar Mass

One mole each of some familiar substances:

sulfur (left)

copper (middle)

mercury (right)

helium (in balloon)

NA = 6.0221415 x 1023

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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

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?

3) 8

B. How many oranges in 2.0 meps?

3) 16

C. How many meps contain 40 gummy bears?

1) 5

Solution

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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

Learning Check

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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

Solution

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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

Molar Mass

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Give the molar mass to 0.1 g

A. 1 mole of Br atoms = ________

B. 1 mole of Sn atoms = ________

Learning Check

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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

Solution

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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 = 92.0 g/mole

2 moles N x 14.0 g/mole + 4 moles O x 16.0 g/mole

Molar Mass of Compounds

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A. 1 mole of K2O = ______g

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

Learning Check

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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

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

1) 40.0 g/mole

2) 262 g/mole

3) 309 g/mole

Learning Check

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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)

Solution

20

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

Learning Check

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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

Solution

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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

Molar Mass Factors

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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

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 = 60.0 g acetic acid

1 mole acetic acid or 60.0 g acetic acid

60.0 g acetic acid 1 mole acetic acid

Solution

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molar mass

Grams Moles

Calculations with Molar Mass

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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

Moles and Grams

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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

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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?

Learning Check

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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

Solution