1. Atoms & Moles

2. The Mole: A Measurement of Matter
Counting the number of atoms of a substance would very time consuming, because the objects you are counting are so small.
Imagine counting all the grains of sugar you baked into a cake. It would take a really long time!
The mole (mol) is one of the seven base units in the SI system and allows us to easily measures the amount of particles in a substance, even though they are very small.
Atoms in garnet, a semi-precious mineral

3. How big is a Mole?
6.02 X 1023 Watermelon Seeds: Would be found inside a melon slightly larger than the moon X 1023 Donut Holes: Would cover the earth and be 5 miles (8 km) deep X 1023 Pennies: Would make at least 7 stacks that would reach the moon X 1023 Grains of Sand: Would be more than all of the sand on Miami Beach X 1023 Blood Cells: Would be more than the total number of blood cells found in every human on earth.

4. 1 mole = 6.02 x 1023 representative particles
Avogadro’s Number
6.02 x 1023 is called Avogadro’s number. It is named after Amadeo Avogadro who did work in the 1800’s that allowed x 1023 to be calculated and is equal to one mole.
The mole is the “chemist’s dozen”. It is a convenient way to count extremely large numbers of atoms, molecules or ions.
1 mole = 6.02 x 1023 representative particles

5. Representative Particles
The form in which a substance exists is its “representative particle”.
Representative particles can be atoms, ions, molecules, formula units, or anything else.
Substance
Representative Particle
Element
Atom

6. Solving Problems with Avogadro’s Number
We work these problems using dimensional analysis.
1 mole = 6.02 x 1023 representative particles
Representative Particles: unit needs to
be applicable to what is being
calculated.

7. How many moles are 1.20 x 1025 atoms of phosphorous?
1.20 x 1025 atoms P
1 mol P x 1
6.02 x 1023 atoms P
19.9 mol P

8. How many atoms are in 0.750 mol of Zn?
0.750 mol Zn
6.02 x 1023 atoms Zn x 1
1 mol Zn
4.52 x 1023 atoms Zn

9. Mole-Mass Relationships

10. Molar Mass (grams)
The molar mass of a singular atom is simply equal to its atomic mass in grams.
Example:
The molar mass of Sulfur is g

11. Mole – Mass Conversions
Conversion factor
1 mol = molar mass (g)

12. Find the mass in grams of 3.32 mol of K.
3.32 mol K
39.10 g K x 1
1 mol K
= x 102 g K

13. Find the number of moles in 187 g of aluminum.
187 g Al
1 mol Al x 1
26.98 g Al
= 6.93 mol Al

14. Multi-step Mole Problems
Using multiple conversion factors.

15. Calculate the number of atoms present in 4.29 g of phosphorous.
4.29 g P
1 mol P
6.02x1023 atoms P x x 1
g P
1 mol P
= 8.34 x 1022 atoms P

16. Calculate the mass of 2.410 x 1022 atoms of gold.
2.410 x 1022 atoms Au
1 mol Au
g Au x x 1
6.02 x 1023 atoms Au
1 mol Au
= g Au