1. The Mole (Chapter 10)
Dr. Walker

2. The Mole in Chemistry
Not this!!
Not this!!!

3. The Mole The mole is a counting unit 1 pair = 2 1 dozen = 12
1 mole = x 1023 atoms
This number is known as Avogadro’s number after Italian chemist Amedeo Avogadro

4. The mole One mole can be equal to three different things
6.022 x 1023 atoms
The atomic mass in grams of an atom or compound
22.4 L (volume) of any gas at 25 oC and 1 atm pressure (known as STP)

6. Molar Mass
The atomic mass of any element is the weighted average of all isotopes of an element
This is also the molar mass of the element
Examples
H = 1.01 g/mole
O = g/mole
C = g/mole
P = g/mole
Cl = g/mole

7. Molar Mass
The molar mass of a compound is the sum of all atomic weights of all atoms in the compound!

8. Molar Mass Examples For compounds H2O H = 1.01 g/mole x 2
O = g/mole x 1
=18.02 g/mole

9. Molar Mass Examples Another example CH4 C = 12.01 g/mole = 12.01
H = 1.01 g/mole x 4 = 4.04
16.05 g/mole

10. Molar Mass Examples Another Example C6H12O6
C = g/mole x 6 = 72.06
H = 1.01 g/mole x 12 = 12.12
O = g/mole x 6 = 96.00
g/mole

11. Molar Mass Examples Another Example Polyatomics Pb(SO4)2 Pb = 207.20
S = g/mole x 2 = 64.14
O = g/mole x 8 =
g/mole
Notice you must multiply the subscript inside the parentheses by the number outside to get the right number of atoms

12. Practice Find the molar mass of the following compounds: LiOH SO2
Mg(NO3)2
Al2(CO3)3
C9H8O4
C8H10N4O2
C22H30N6O4S

13. Practice Find the molar mass of the following compounds: LiOH
= g/mole
SO2
(16.00) = g/mole
Mg(NO3)2
(14.01) + 6(16.00) = g/mole
Al2(CO3)3
2(26.98) + 3(12.01) + 9(16.00) = g/mole
C9H8O4
9(12.01) + 8(1.01) + 4(16.00) = g/mole
C8H10N4O2
8(12.01) + 10(1.01) + 4(14.01) + 2(16.00) = g/mole
C22H30N6O4S
22(12.01) + 30(1.01) + 6(14.01) + 4(16.01) + 1(32.06) = g/mole

14. Mass-Mole Conversions
Convert from mass to mole (or vice versa) using the molar mass of a given element or compound
Use dimensional analysis (t-square)

15. Mass-Mole Conversions
How many grams are in 2.5 moles NH3?

16. Mass-Mole Conversions
How many grams are in 2.5 moles NH3?
Find molar mass of NH3
N = g/mole x 1 = g/mole
H = 1.01 g/mole x 3 = 3.03 g/mole
Molar mass = g/mole
Multiply # of moles by molar mass
2.5 moles NH3
17.04 g NH3
= g NH3
1 mole NH3

17. Mass-Mole Conversions
How many moles are contained in 100 g C3H8?

18. Mass-Mole Conversions
How many moles are contained in 100 g C3H8?
Find molar mass
C = g/mole x 3 = g/mole
H = 1.01 g/mole x 8 = 8.08 g/mole
44.11 g/mole
Divide # of grams given by molar mass
100 g C3H8
1 mole C3H8
= 2.27 moles C3H8
44.11 g C3H8

19. Mass-Mole Conversions
How many grams are present in 3.1 moles of lithium carbonate?

20. Mass-Mole Conversions
How many grams are present in 3.1 moles of lithium carbonate?
Formula for lithium carbonate = Li2CO3
Li = 6.94 g/mole x 2 = g/mole
C = g/mole x 1 = g/mole
O = g/mole x 3 = g/mole
73.89 g/mole
Multiply number of moles by molar mass
3.1 moles Li2CO3
73.89 g Li2CO3
= g Li2CO3
1 mole Li2CO3

21. Mole-Particle conversions
Can go to or from moles from particles
Atoms in an element
Molecules in a covalent compound
You may see other terms like ions, formula units
1 mole = x 1023 particles is the conversion factor that you use

22. Mole-Particle Conversions
How many atoms are in 1.5 moles of iron?

23. Mole-Particle Conversions
How many atoms are in 1.5 moles of iron?
1.5 moles iron
6.022 x 1023 atoms iron
= 9.03 x 1023 atoms iron
1 mole iron

24. Mole-Particle Conversions
How many moles are in 2.4 x 1024 molecules of water?

25. Mole-Particle Conversions
How many moles are in 2.4 x 1024 molecules of water?
2.4 x 1024 molecules H2O
1 mole H2O
= 3.98 moles H2O
6.022 x 1023 molecules H2O

26. Mole-Particle Conversions
It doesn’t matter what atom or compound is being converted
For these conversions, you are always using 1 mole = x 1023 particles as your conversion factor!!

27. Mole-Volume Conversions
At a specific set of conditions (known as Standard Temperature and Pressure or STP), 1 mole of any gas = 22.4 L of volume
We can convert volume to moles and vice versa

28. Example
How many liters of O2 are contained in 5.0 moles?

29. Example How many liters of O2 are contained in 5.0 moles? 5.0 moles O2
22.4 L O2
= 112 L O2
1 mole O2

30. Example
How many moles are contained in a 3.7 L sample of N2?

31. Example How many moles are contained in a 3.7 L sample of N2? 3.7 L N2
1 mole N2
= 0.17 moles N2
22.4 L N2

32. Multistep Conversions
We know that the mole is equal to multiple numbers ( Avogadro’s # = 1 mole = molar mass = 22.4 L)
Given this fact, we can convert from particles to mass using the mole
Hint: If you look at the problem and the word “mole” is absent, it is multistep!!

33. Multistep Example
How many grams are present in a 10 L sample of H2?

34. Multistep Example How many grams are present in a 10 L sample of H2?
Convert from liters to moles
Convert from moles to grams
10 L H2
1 mole H2
22.4 L H2

35. Multistep Example How many grams are present in a 10 L sample of H2?
Convert from liters to moles
Convert from moles to grams
10 L H2
1 mole H2
2.02 g H2
= g H2
22.4 L H2
1 mole H2

36. Example
How many molecules are contained in 4.5 g H2O?

37. Example How many molecules are contained in 4.5 g H2O? Step 1
Convert from grams to moles
4.5 g H2O
1 mole H2O
18 g H2O

38. Example How many molecules are contained in 4.5 g H2O? Step 2
Convert from moles to particles
0.25 moles H2O
6.022 x 1023 molecules H2O
4.5 g H2O
1 mole H2O
= 1.50 x 1023 molecules H2O
18 g H2O
1 mole H2O

39. Vocab/Skills Vocabulary Skills Molar Mass Avogadro’s number
Convert to and from moles using mass/particles/volumes using dimensional analysis