1. The Mole
Chapter 11

2. Counting large numbers…
Easier when you use counting units:
Dozen
Ream
Pair
Case
Gross
Regardless of the object, the number that the units represents is always the same

3. Atoms and molecules are extremely small
Impossible to actually count them (even in the smallest of samples)
Chemists need a unit for counting accurately the # of atoms, molecules, or formula units
They use the mole
Mole (mol) = the SI base unit used to measure the amount of a substance
1 mole of anything contains 6.02 x 1023 representative particles

4. 1 mole of apples =
6.02 x 1023 apples
1 mole of diamonds =
6.02 x 1023 diamonds
1 mole of baseballs =
6.02 x 1023 baseballs
1 mole of carbon atoms =
6.02 x 1023 carbon atoms

5. The same applies to moles of compounds
How many molecules are in 1 mol NH3?
6.02 x 1023 NH3 molecules
How many molecules are in 1 mol C9H8O4?
6.02 x 1023 C9H8O4 molecules

6. Amedeo Avogadro determined the volume of one mole of gas in 1811
6.02 x 1023
Known as Avogadro’s number
Where did it come from?
Amedeo Avogadro determined the volume of one mole of gas in 1811

7. Converting Moles to Particles and Particles to Moles
How many roses are in 3 ½ dozen?
USE CONVERSION FACTORS!!!
3.5 dozen x 12 roses =
1 dozen
42 roses
How many pencils are in 6 gross?
6 gross x 144 pencils =
1 gross
864 pencils

8. Converting Moles to Particles and Particles to Moles
How many particles of sucrose are in 3.50 moles of sucrose?
3.50 mol sucrose x x 1023 rep. part.
1mol
2.11 x 1024 particles of sucrose

9. Converting Moles to Particles and Particles to Moles
How many moles contain 4.50 x 1024 atoms of zinc?
4.50 x 1024 atoms Zn x 1 mol zinc
6.02 x 1023 atoms Zn
7.48 mol Zn

11. Try some on your own… How many Cu atoms are in 1.20mol Cu?
7.22 x 1023 Cu atoms
How many moles of Xe contain 1.54 x 1026 atoms of Xe?
2.56 x 102 mol Xe

12. Mass and the Mole Mass of dozen limes = Mass of dozen eggs
Moles of substances have different masses, due to the differing sizes and compositions
1 mol of C vs. 1 mol of Cu
Molar mass= the mass in grams of one mole of any pure substance

13. The molar mass of any element is numerically equal to its atomic mass and has the units g/mol
Ex:
one atom of Manganese = 54.94amu
molar mass of Manganese = 54.94g/mol
So, when you measure out g of manganese on a balance you are actually measuring out 6.02 x 1023 atoms of manganese
Look at figure 11-4 in your textbook

14. Using Molar Mass Jellybean example Jelly beans sold by the dozen
1 doz jelly beans = 35 g
If a customer wants 8 dozen jelly beans, should you count out 96 individual jelly beans or could you USE A CONVERSION FACTOR?

15. Yep…you guessed it…use a conversion factor!!
You could figure out the mass of 8 dozen jelly beans and measure the mass
8 doz jelly beans x 35 g jelly beans
1doz jelly beans
= 280 g of jelly beans

16. Try one on your own…
A customer comes into your candy store and wants 16 doz jelly beans, use a conversion factor to figure out how many grams you should measure out.
16 doz x 35 g
1 doz
= 560 g jelly beans

17. Apply it to working in a chemistry lab…
You are a lab assistant and want mol of chromium. Using a conversion factor, calculate the mass in grams of mol of chromium.
Molar mass of chromium = 52.00g/mol
0.0450mol x 52.00g
1 mol
= 2.34 g Cr
You would need to measure out 2.34 g of Chromium

18. Try one on your own…
You need 3.0 moles of Mn for a chemical reaction. Calculate how many grams of Mn you would need to measure out.
3.0mol x 54.9g
1mol
= 165g Mn

19. You know how to convert moles to mass, let’s try converting mass to moles!!
Use the inverse of the conversion factor!!
Let’s say you have 200g of Mn. How many moles do you have?
200g x 1mol
54.9g
= 3.64mol Mn

20. Let’s do some more converting!!

21. Your boss is so impressed with your skills that he gives you a raise!!
Mass to atoms
You are back at the candy store and at the end of the day you have 910g of jelly beans left. Your boss wants to know how many jellybeans this is. Rather that count out the individual candies, you decide to use your superior brain power and calculate it mathematically!!
910g x 1 doz
35g
= 26 doz jelly beans left
Your boss is so impressed with your skills that he gives you a raise!!

22. How many atoms of gold are in a pure gold nugget with a mass of 25.0g?
Now try it with atoms…
How many atoms of gold are in a pure gold nugget with a mass of 25.0g?
You can’t go directly from mass to atoms, so you have to convert to moles first
25.0g x 1mol
196.7g
= mol Au
0.127mol x 6.02 x 1023 atoms
1mol
= 7.65 x 1022 atoms of Au

24. Chemical Equations
Coefficients in a chemical equation represent the numbers of individual particles of substances in the equation
…they also represent the numbers of moles of particles
C3H8 + 5O2  3CO2 + 4H2O

25. Mole Ratios
Mole ratio = ratio between the numbers of moles of any two substances in a balanced chemical equation
C3H8 + 5O2  3CO2 + 4H2O

26. 2Al + 3Br2  2AlBr3 What mole ratios can be written for this reaction?
2mol Al mol Br2
3molBr mol AlBr2
2mol Al molAlBr3
2molAlBr Al
3mol Br molAlBr3
2mol Al molBr2

27. Chemistry Matter and Change
Courtesy of
Chemistry Matter and Change
Glencoe McGraw-Hill
Chemistry for Dummies
John T. Moore