1. The Mole, Mass & Formulas
Dr. Ron Rusay
Chem 106
Spring 2004
© Copyright 2004 R.J. Rusay

2. The Mole
Definition: The number of carbon atoms in exactly 12 grams of pure 12C. The number equals  atoms.
1 mole = 6.02  units
6.02  “units” of anything: atoms, people, stars, $s, etc., etc. = 1 mole
There are about 6.2 billion people in the world.
How many moles of people are there?

3. Avogadro’s number equals 1 mole ….which equals
Avogadro’s number equals 1 mole ….which equals
6.022  1023 “units”
How many molecules are there in 0.5 moles of oxygen?
What do you get if you divide an avocado into 6.02 x pieces?
guaca-mole!

4. Calculate the number of atoms of silicon in 0.367 moles of silicon.
a) 6.10 x atoms Si
b) 2.21 x atoms Si
c) 2.21 atoms Si
d)1.64 x atoms Si
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

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

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

7. 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

8. 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

9. 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

10. 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

11. Calculate the molar mass of potassium phosphate.
a) 134 g/mol
b) g/mol
c) g/mol
d) g/mol
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

12. Calculate the mass in grams of 4.00 moles of sulfur.
a) 128 g
b) g
c) 12.5 g
d) g
What do you need ?
Atomic Weight sulfur (S) = 32.07
(molar mass) = g/mol
4 mol sulfur x g/mol sulfur =
128.3 g

13. 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%

14. Calculate the percentage composition for all the elements in nicotine, C10H14N2.
a) 64.14% C, 14.04% H, 21.82% N
b) % C, % H, % N
c) % C, 8.71 % H, % N
d) % C, 3.74 % H, % N
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% % %

15. 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.

16. Formulas: Multiple Proportions

17. 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

18. Formulas & Molecular Representations
molecular formula = C6H6 Benzene
empirical formula = CH = C6/6H6/6
molecular formula = (empirical formula)n
[n = integer] (CH)6
Other representations: Lewis Dot formulas, structural formulas, 2-D, 3-D

19. Formulas & Molecular Representations

20. Structural Representations of Quinine

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
What is the road map for a dimensional solution?
Rank the analgesics in biological activity from highest to lowest.