1. CHEM 108
The Mole / Molar Mass
and
Molecular Formulas

2. Moles & Mass How big is a mole?
(Not the animal, the other one.) - Daniel Dulek

3. The Mole
Definition: The number of carbon atoms in exactly 12 grams of pure 12C. The number equals  atoms.
1 mole = 6.02  units of anything
6.02  “units” of atoms, people, ants, stars, $$$s, etc., etc. = 1 mole
There are about 7.4 billion people in the world.
How many moles of people are there?

4. 6.02  10 23 people = 1 mole 1 mole = 6.02  10 23 units of anything
There are about 7.4 billion people in the world.
How many moles of people are there?
1 mole = 6.02  units of anything
6.02  people = 1 mole
7.4 x 10 9 people / 6.02 x people / 1 mol =
1.2 x mol

5. Avogadro’s number equals 1 mole ….which equals
6.022  1023 “units”
How many molecules are there in one half mole of oxygen?
3.011  1023 molecules of oxygen

6. Calculate the number of atoms of silicon in 0.367 moles of silicon.
What do you need ?
Avogadro’s Number
1 mole = 6.02 x atoms
0.367 mol x x atoms / 1 mol =
2.21 x atoms Si
What do you get if you divide an avocado into 6.02 x pieces?
guaca-mole!

7. Counting by Weighing 12 red marbles @ 7g each = 84g
12 yellow 4g each=48g
55.85g Fe = x 1023 atoms Fe
32.07g S = x 1023 atoms S
Consult the Periodic Table

8. Relative Masses of 1 Mole
CaCO3 Name? g
Oxygen
32.00 g
Copper
63.55 g
Water
18.02 g
1 mole of an “ideal” gas
equals
22.4 Liters.
(A balloon diameter
of 35 cm.)
What is the volume of
1 mole of water?

9. Atomic and Molecular Weights Mass Measurements
1H weighs x g and 16O x g.
DEFINITION: mass of 12C = exactly 12 amu.
Using atomic mass units:
1 amu = x g
1 g = x 1023 amu

10. Atomic and Molecular Weights
Formula Weight a.k.a. Molecular Weight
Formula weights (FW): sum of Atomic Weights (AW) for atoms in formula.
FW (H2SO4) = 2AW(H) + AW(S) + 4AW(O)
= 2(1.0 amu) + (32.0 amu) + 4(16.0)
= amu

11. Atomic and Molecular Weights
Molecular weight (MW) is the weight of the molecular formula in amu.
MW of sugar (C6H12O6 ) = ?
MW = 6(12.0 amu) + 12(1.0 amu) + 6(16.0 amu)
= 180 amu

12. Molar Mass
A substance’s molar mass is the mass in grams of one mole of the element or compound. (Equals the formula weight: atomic or molecular weight in grams)
Molar Mass CO2 = ?
C = grams per mole (g/mol)
O = grams per mole (g/mol)
CO 2 = grams per mole (g/mol) (16.00) = 44.01

13. Calculate the molar mass of potassium phosphate.
What do you need ?
1) Formula of potassium phosphate:
K3PO4
2) Atomic Weights
(molar mass)
K = 39.10, P = 30.97, O = 16.00
3(39.10) (16.00) =
g/mol

14. Calculate the mass in grams of 4.00 moles of sulfur.
What do you need ?
Atomic Weight sulfur (S) = 32.07
(molar mass) = g/mol
4 mol sulfur x g/mol sulfur =
128.3 g

15. Percent Composition Mass percent of an element:
For iron in (Fe2O3), iron (III) oxide = ?
Which iron ore would you buy: one high in Fe2O3 or one high in FeO, Iron (II) oxide?
55.84 / x 100 = 77.7%

16. Calculate the percentage composition for all the elements in an alkaloid with the molecular formula C10H14N2.
What do you need ?
Molar mass C10H14N2
C = 12.01, H = 1.01, N = 14.01
10(12.01) + 14(1.01) + 2(14.01) = g/mol
120.1g/mol g/mol g/mol
120.1/ / /
x 100 = x 100 = x 100 =
74.02% % %

17. Formulas: Dalton’s Law
Dalton’s law of multiple proportions:
When two elements form different compounds, the mass ratio of the elements in one compound is related to the mass ratio in the other by a small whole number.

18. Formulas: Multiple Proportions

19. Formulas & Multiple Proportions Components of acid rain, SO2(g) and SO3(g)
Compound A contains:
1.000 g Sulfur & g Oxygen
Compound B contains:
1.000 g Sulfur & g Oxygen
Mass ratio A: 1 to 1.5; Mass ratio B: 1 to 1
MUST adjust for atomic mass differences: AW sulfur is 2x the AW oxygen; therefore the oxygen ratios are 2x sulfur.
S1O3 and S1O2 respectively

20. Compounds with the Same Formula
[ eg. C9H8O4 ]
Aspirin
4-Hydroxyphenylpyruvic acid
Dihydroxycinnamic acids:
Caffeic acid (3,4-dihydroxycinnamic acid)
Umbellic acid (2,4-dihydroxycinnamic acid)
2,3-Dihydroxycinnamic acid
2,5-Dihydroxycinnamic acid
3,5-Dihydroxycinnamic acid
Aspirin: NSAIDS COX enzymes
Plant phenolics/ flavonoids: prevention of cancer, allelopathy, antioxidants
Caffeic acid can be found in the bark of Eucalyptus globulus.[3] It can also be found in the freshwater fern Salvinia molesta[4] or in the mushroom Phellinus linteus.[5]
Caffeic acid is found at a very modest level in coffee, at 0.03 mg per 100 ml.[6] It is one of the main natural phenols in argan oil.[7]
It is found at high level in some herbs, especially thyme, sage and spearmint (at about 20 mg per 100 grams), at high levels in spices, especially Ceylon cinnamon and star anise (at about 22 mg per 100 grams), found at fairly high level in sunflower seeds (8 mg per 100 grams), and at modest levels in red wine (1.88 mg per 100 ml) and in applesauce, apricot and plum prunes (at about 1 mg per 100 grams). It is at super high level in black chokeberry (141 mg per 100 grams) and in fairly high level in lingonberry (6 mg per 100 grams).[6] It is also quite high in the South American herb yerba mate

21. Molar Comparisons of Analgesics Moles : Doses (mmol/dose)
Which analgesic has the most biologically active ingredient based on millimoles per dose (mmol/dose)?
5.0 g of each would produce the following number of doses:
Formula Doses mmol/dose
Aspirin C9H8O
Ibuprofen C13H18O2 25
Naproxen Sodium C14H13O3Na 22.7
Acetaminophen C8H9NO2 5
Molar Mass Aspirin = g/mol
5.0 g / g/mol = mol = 28 mmol