1. Chapter 5 Chemical Quantities and Reactions
5.1
The Mole

2. Counting Units Counting units
A counting term states a specific number of items.
1 dozen eggs = 12 eggs
1 case soda = 24 cans
1 ream = 500 sheets of paper

3. Avogadro's Number
Small particles such as atoms, molecules, and ions are
counted using the mole.
1 mole = 6.02 x 1023 items
Avogadro’s number
= 6.02 x 1023

4. Mole of Atoms 1 mole of an element = 6.02 x 1023 atoms of that element
1 mole of carbon = 6.02 x 1023 atoms of carbon
1 mole of sodium = 6.02 x 1023 atoms of sodium

5. Number of Particles in One-Mole Samples

6. Avogadro's Number Avogadro’s number, 6.02 x 1023, can be written as an
equality and as two conversion factors.
Equality:
1 mole = x 1023 particles
Conversion Factors:
6.02 x 1023 particles and mole
1 mole x 1023 particles

7. Guide to Calculating Atoms or Molecules

8. Converting Moles to Particles
Avogadro’s number is used to convert moles of a
substance to particles.
How many CO2 molecules are
in 0.50 mole of CO2?
Step 1 State the needed and given quantities:
Given: mole of CO2
Needed: molecules of CO2

9. Converting Moles to Particles
Step 2 Write a plan to convert moles to atoms or molecules:
Avogadro’s number
moles of CO molecules of CO2
Step 3 Use Avogadro’s number to write conversion factors.
1 mole of CO2 = 6.02 x 1023 molecules of CO2
6.02 x 1023 CO2 molecules and mole CO2
 1 mole CO x 1023 CO2 molecules

10. Converting Moles to Particles
Step 4 Set up the problem to calculate the number of particles.
0.50 mole CO2 x x 1023 molecules CO2
1 mole CO2
= 3.01 x 1023 molecules of CO2

11. Learning Check The number of atoms in 2.0 mole of Al atoms is:
A Al atoms
B x 1023 Al atoms
C x 1024 Al atoms

12. Solution The number of atoms in 2.0 moles of Al atoms is:
Step 1 State the needed and given quantities:
Given: mole Al
Needed: atoms of Al
Step 2 Write a plan to convert moles to atoms or molecules:
Avogadro’s number
Moles of Al Atoms of Al

13. Solution The number of atoms in 2.0 moles of Al atoms is:
Step 3 Use Avogadro’s number to write conversion factors.
1 mole of Al = 6.02 x 1023 atoms of Al
6.02 x 1023 atoms Al and mole A
1 mole Al x 1023 atoms Al

14. Solution The number of atoms in 2.0 moles of Al atoms is:
Step 4 Set up the problem to calculate the number
of particles.
C moles Al x x 1023 Al atoms
1 mole Al
= 1.2 x 1024 Al atoms

15. Learning Check The number of moles of S in 1.8 x 1024 atoms of S is:
A mole of S atoms
B moles of S atoms
C x 1048 moles of S atoms

16. Solution The number of moles of S in 1.8 x 1024 atoms of S is:
Step 1 State the needed and given quantities:
Given: x 1024 atoms of S
Needed: moles of S
Step 2 Write a plan to convert moles to atoms or molecules:
Avogadro’s number
Atoms of S Moles of S

17. Solution The number of moles of S in 1.8 x 1024 atoms of S is:
Step 3 Use Avogadro’s number to write conversion factors.
1 mole S = 6.02 x 1023 atoms of S
6.02 x 1023 atoms S and mole S
1 mole S x 1023 atoms S

18. Solution The number of moles of S in 1.8 x 1024 atoms of S is:
Step 4 Set up the problem to calculate the number of particles.
B. 1.8 x 1024 S atoms x mole S
6.02 x 1023 S atoms
= 3.0 moles of S atoms

19. Moles of Elements in a Formula

20. Moles of Elements in a Formula
The subscripts in a formula show:
the relationship of atoms in the formula
the moles of each element in 1 mole of compound
Aspirin
C9H8O4
1 molecule: 9 atoms of C 8 atoms of H atoms of O
1 mole: moles of C 8 moles of H moles of O

21. Moles of Elements in a Formula
Subscripts are used to write conversion factors for
moles of each element in 1 mole of a compound. For
aspirin, C9H8O4, the possible conversion factors are:
9 moles C moles H moles O
1 mole C9H8O mole C9H8O mole C9H8O4
9 moles C moles H moles O

22. Learning Check
How many atoms of O are in mole of aspirin, C9H8O4?

23. Solution Step 1 State the needed and given quantities:
Given: mole of C9H8O4
Need: molecules of C9H8O4
Step 2 Write a plan to convert moles to atoms or molecules:
Moles of aspirin Moles of O Atoms of O

24. Solution Step 3 Use Avogadro’s number to write conversion factors.
Subscript factor: 1 mole of C9H8O4 = 4 moles of O
1 mole C9H8O and moles O
4 moles O mole C9H8O4
Avogadro’s number:
1 mole of O = 6.02 x 1023 atoms of O
1 mole O and x 1023 atoms O
6.02 x 1023 atoms O mole O

25. Solution
Step 4 Set up the problem to calculate the number of particles.
0.150 mole C9H8O4 x 4 mole O x x 1023 atoms O
1 mole C9H8O mole O
= x 1023 atoms of O