1. Chapter 7 Chemical Quantities
7.1 The Mole
Learning Goal Use Avogadro's number
to determine the number of particles in
a mole.
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2. Calculating a Percentage (1.4C) Solving Equations (1.4D)
Chapter 7 Readiness
Key Math Skills
Calculating a Percentage (1.4C)
Solving Equations (1.4D)
Using Scientific Notation (2.2)
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3. Counting Significant Figures (2.3)
Chapter 7 Readiness
Core Chemistry Skills
Counting Significant Figures (2.3)
Using Significant Figures in Calculations (2.4)
Writing Conversion Factors from Equalities (2.6)
Using Conversion Factors (2.7)
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4. The Mole Counting Units 1 dozen = 12 1 case = 24 cans
Avogadro’s number
= × 1023
Atoms are so small it takes a large number of them to weigh and use in a chemical reaction.
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5. One mole of any element contains 6.022 × 1023 atoms of that element.
Avogadro’s Number
A mole (mol) is a unit that represents the same number of particles as there are carbon atoms in g of carbon.
One mole of any element contains × 1023 atoms of that element.
1 mol of Element Number of Atoms
1 mol C = × 1023 C atoms
1 mol Au = × 1023 Au atoms
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6. an element contains 6.022 × 1023 atoms
Avogadro’s Number
One mole of
an element contains × 1023 atoms
a molecule contains × 1023 molecules
an ion contains × 1023 ions
a formula unit contains
6.022 × 1023 formula units
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7. Number of Particles in One Mole
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8. Avogadro’s number as a Conversion Factor
Avogadro’s number (6.022 × 1023) can be written as an equality and two conversion factors.
Equality: mole = × 1023 particles
Conversion Factors:
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9. Using Avogadro’s Number
Avogadro’s number converts moles of a substance to the number of atoms.
How many Cu atoms are in 0.50 mol of Cu?
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10. Using Avogadro’s Number
Avogadro’s number converts the number of molecules to moles of a molecule.
How many moles of CO2 are in 2.50 × 1024 molecules of CO2?
2.50 × 1024 molecules CO2
= mole CO2
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11. Guide to Calculating the Atoms or Molecules of a Substance
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12. The number of atoms in 2.0 moles of aluminum is A. 2.0 Al atoms
Learning Check
The number of atoms in 2.0 moles of aluminum is
A Al atoms
B × 1023 Al atoms
C × 1024 Al atoms
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13. Solution
The number of atoms in 2.0 moles of aluminum is Step 1 State the given and needed quantities. Given = 2.0 moles Al Need = atoms of Al Step 2 Write a plan to convert moles to atoms. Moles Al atoms Al
Avogadro’s Number
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14. The number of atoms in 2.0 moles of aluminum is
Solution
The number of atoms in 2.0 moles of aluminum is
Step 3 Use Avogadro’s number to write conversion factors.
Equality: 1 mole Al = × 1023 atoms Al
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15. The number of atoms in 2.0 moles of aluminum is
Solution
The number of atoms in 2.0 moles of aluminum is
Step 4 Set up the problem to calculate the number of particles
= 1.2 × 1024 atoms Al
Answer C is correct.
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16. Moles of Element in a Chemical Formula
The subscripts in a formula state
the relationship of atoms in the formula
the moles of each element in one mole of compound
NH3
1 molecule 1 atom N 3 atoms H
1 mole NH3 1 mole N 3 moles H
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17. Chemical Formulas, Subscripts
Aspirin, C9H8O4, is used to reduce pain and inflammation.
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18. Chemical Formulas, Subscripts
The subscripts in the chemical formula for aspirin, C9H8O4, express the ratio of atoms or moles.
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19. Chemical Formulas, Conversion Factors
The subscripts from the formula, C9H8O4, can be used in conversion factors.
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20. Guide to Calculating Moles
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21. How many moles of carbon are present in 2.50 moles of aspirin, C9H8O4?
Learning Check
How many moles of carbon are present in 2.50 moles of aspirin, C9H8O4?
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22. Solution
How many moles of oxygen are present in 2.50 moles of aspirin, C9H8O4? Step 1 State the given and needed quantities. Given: 2.50 moles aspirin, C9H8O4 Need: moles of O Step 2 Write a plan to connect moles of a compound to moles of an element. moles C9H8O4 moles O
Subscript
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23. Solution
How many moles of oxygen are present in 2.50 moles of aspirin, C9H8O4? Step 3 Write equalities and conversion factors. 1 mole C9H8O4 = 4 moles O
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24. How many moles of oxygen are present in 2.50 moles of aspirin, C9H8O4?
Solution
How many moles of oxygen are present in
2.50 moles of aspirin, C9H8O4?
Step 4 Set up the problem to calculate the moles of an element.
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25. Learning Check
The number of moles of sulfur (S) in 1.8 × 1024 atoms of sulfur is _____.
A mol of S atoms
B mol of S atoms
C × 1048 mol of S atoms
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26. The number of moles of sulfur (S) in 1.8 × 1024
Solution
The number of moles of sulfur (S) in 1.8 × 1024
atoms of sulfur is _____.
Step 1 State the given and needed quantities.
Given: 1.8 × 1024 atoms of S
Need: moles of S
Step 2 Write a plan to connect moles to atoms or molecules.
atoms S moles S
Avogadro's number
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27. Step 3 Use Avogadro’s number to write conversion factors.
Solution
The number of moles of sulfur (S) in 1.8 × 1024 atoms of sulfur is _____.
Step 3 Use Avogadro’s number to write conversion factors.
1 mole S = × 1023 atoms
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28. Step 4 Set up the problem to calculate the number of particles.
Solution
The number of moles of sulfur (S) in 1.8 × 1024 atoms of sulfur is _____.
Step 4 Set up the problem to calculate the number of particles.
The correct answer is B.
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