1. The Mole!

2. Amadeo Avogadro Avogadro’s Number The Mole
Italian Lawyer, Physics/Chem.
on the side
Made observations using gases, how they combined
Hypothesized that different gases in the same volume contained the same number of total gas molecules
Avogadro’s Number
he died in 1856
other scientists quantified his observations

3. Quantity of measurement used for atoms and/or molecules
The Mole
Quantity of measurement used for atoms and/or molecules
A dozen eggs, a ream of paper, a barrel of pennies
Need to have some concrete number to know what that quantity means
dozen = 12
ream = 500 sheets (of normal paper)
barrel of pennies = 24, 216 pennies

4. Atoms are extremely small
The Mole
Atoms are extremely small
Not practical (or possible) to count each one
If nucleus was 1mm, electron cloud would be as tall as Empire State Building
Would barrel of pennies example work if barrel had nickels, dimes and quarters too?
NO! It has to be all the same thing, pennies
A PURE SUBSTANCE
an atom of ONE element or a molecule of a compound

5. 6.02 x 1023 A dozen tells us how much of “something” we have
The Mole
A dozen tells us how much of “something” we have
We know that a dozen is 12 of “something”
A Mole tells us the same thing
Instead of 12, a mole is equal to…
6.02 x 1023

6. Avogadro’s number is 6.02 x 1023 of ANY “elementary entity”
The Mole
Avogadro’s number is 6.02 x 1023 of ANY “elementary entity”
elements – atoms
compounds- molecules/formula units
gorillas- one gorilla
One Mole of atoms = 6.02 x atoms
One Mole of molecules = 6.02 x molecules
One Mole of gorillas = 6.02 x gorillas

7. The Mole
How big is 6.02 x 1023?
It would take 1.9 x 1016 YEARS to count a mole (one per second)

8. The Mole
How big is
6.02 x 1023?
You would need more than 31 trillion stacks of paper that would stretch from the Earth to the Moon to have a mole of sheets of paper

9. Molar Mass The Mole H2O Mass, in grams, of one mole of a substance
For an element: (Neon)
-equal to the atomic mass, units = grams/mole
For a compound find mass of each element, multiply it by the subscript, add all components together:
H = 1g x 2 = 2g
H2O
O = 16g x 1 = 16g
TOTAL = 18 g/mol
MOLAR MASS OF ONE WATER MOLECULE

10. The Mole Examples: Find the number of moles in 47 grams of Oxygen
1 mol O2
32 grams
47 x 1 = 47
47 ÷ 32 =
Moles O2

11. The Mole
Examples:
Find the number of molecules in 1.46 moles of Oxygen
1.46 mol O2
6.02 x 1023 molecules O2
1 mol O2
1.46 x x 1023 = 8.79 x 1023
8.79 x 1023 ÷ 1 = 8.79 x 1023
molecules O2

12. Molar Volume
STP= Standard Temp. & Pressure, which means 0°C or 273K and 1atm or 760mmHg.
At STP (standard temp & pressure) 1 mole of any gas takes up 22.4L.
Ex-
3 moles = ? L
80 L = ? moles

13. The Mole Examples: Find the number of liters in 3 moles of a gas
67.2 ÷ 1 = 67.2
Liters

14. Molar Volume
STP= Standard Temp. & Pressure, which means 0°C or 273K and 1atm or 760mmHg.
At STP (standard temp & pressure) 1 mole of any gas takes up 22.4L.
Ex-
3 moles = 67.2 L
80 L = ? Moles
3.57 Moles

15. The Mole Examples: Find the number of moles in 80 liters of a gas
80 ÷ 22.4 = 3.57
moles

16. Stoichiometry Ratios stay the same The Mole
A process used to compare different measurements and quantities
Greek word that means “element” (Stoichen), “measure” (Metreon)
Ratios stay the same
units and actual value may change
ratio of the components stays the same

17. The Mole Example: recipe for soup that serves 4 people
1.2 lbs of potatoes
.4 lbs of onions
.8 lbs of carrots
.2 lbs of celery
1.4 lbs of water

18. The Mole Example: recipe for soup that serves 4 people
An army
x 1 ton
1.2 tons
1.2 lbs of potatoes
.4 lbs of onions
.8 lbs of carrots
.2 lbs of celery
1.4 lbs of water
x 1 ton
.4 tons
.8 tons
.2 tons
1.4 tons
Ratios are all still the same, even though the total amount is different!

19. Chemical Equations not Soup
The Mole
Chemical Equations not Soup
C + 2S = CS2
Look at atomic mass (periodic table) to find amount of atomic mass units (u) in this equation
12u C + 64u S = 76u CS2
ONE a.m.u. multiplied by 6.02 x 1023 equals ONE gram, so…
12g C + 64g S = 76g CS2

20. The End!