1. Glencoe: Chapter 11 Sections 11.1 & 11.2
The Mole, part I
Glencoe: Chapter 11
Sections 11.1 & 11.2

2. What is a mole?

3. What is a mole?
A mole is a unit for counting very small particles. It is the SI base unit for measuring substances.
Abbreviation: mol
Particles include: molecules, formula units, ions and atoms.

4. In order to count such small particles, a mole has to be a large number.
The value of the mole is:
6.02 * or
602,000,000,000,000,000,000,000
This number is called Avogadro’s number, after Count Amedeo Avogadro, who is credited with its discovery.

5. Mole-Particle & Particle-Mole Conversions
To convert from moles to particles, multiply by Avogadro’s number.
1.5 mol X 6.02*1023 atoms
1 mol
To convert from particles to moles, divide by Avogadro’s number.
1.2 * 1024 atoms X 1 mol
6.02*1023 atoms

6. Molar Mass
The mass in grams of one mole of any substance is its molar mass.
The molar mass of any element is its atomic mass from the periodic table.
The molar mass of any compound is the sum of the molar masses of its component elements.

7. Examples The molar mass of sulfur is 32.06 g/mol.
The molar mass of carbon is g/mol.
The molar mass of sodium chloride is 58.5 g/mol.
The molar mass of water is g/mol.

8. Mole-Mass & Mass-Mole Conversions
To convert from moles to mass, multiply by the molar mass:
2 mol K X g/mol = g K
To convert from mass to moles, divide by the molar mass:
36.04 g H2O / g/mol = 2 mol H2O

9. Mass-Particle & Particle-Mass Conversions
These problems requires two steps.
To convert from mass to particles, divide by the molar mass, then multiply by Avogadro’s number:
25.0 g Au / g/mol = .127 mol Au
.127 mol Au X 6.02 * 1023 atoms = 7.65 * 1022 Au atoms

10. To convert from particles to mass, divide by Avogadro’s number, then multiply by the molar mass:
5.50 * 1022 He atoms / 6.02 * 1023 =
.0914 mol He
.0914 mol He X 4.00 g = .366 g He

11. Percent Composition
In analytical chemistry, it is important to identify the elements in a compound, and determine their percent by mass.
The percent by mass of each element in a compound is called percent composition.
mass of element X 100
mass of compound

12. Complete Handout Problems
To be continued…
Complete Handout Problems