1. 6.02 X 1023 Chemical Composition Adapted from www.chemistrygeek.com
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6.02 X 1023
Adapted from

2. The Mole A counting unit 6.02 X 1023 (in scientific notation)
Dozen
Ream
Gross
Mole
6.02 X 1023 (in scientific notation)
602,000,000,000,000,000,000,000
Avogadro’s Number
Named in honor of Amedeo Avogadro (1776 – 1856)
Equal volumes of any gas will have equal number of molecules

3. Just How Big is a Mole?
Enough soft drink cans to cover the surface of the earth to a depth of over 200 miles.
If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles.
If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

4. Learning Check
Suppose we invented a new collection unit called a rapp. One rapp contains 8 objects.
1. How many paper clips in 1 rapp?
a) 1 b) 4 c) 8
2. How many oranges in 2.0 rapp?
a) 4 b) 8 c) 16
3. How many rapps contain 40 gummy bears?
a) 5 b) 10 c) 20

5. A Mole of Particles Contains 6.02 x 1023 particles
= x 1023 C atoms
= x 1023 H2O molecules
= x 1023 NaCl formula units
(technically, ionics are compounds not molecules so they are called formula units)
6.02 x 1023 Na+ ions and
6.02 x 1023 Cl– ions
1 mole C
1 mole H2O
1 mole NaCl

6. Avogadro’s Number as Conversion Factor
6.02 x 1023 particles
1 mole or
1 mole
Note that a particle could be an atom, molecule or formula unit

7. Mole-Particle Conversions
Convert 12 moles of Hydrogen to atoms -
12 moles x 6.02 x 1023 atoms = 7.22 x 1024 atoms
1 mole
Convert 1.20 x 1024 molecules of Carbon Dioxide to moles
1.20 x 1024 molecules x 1 mole = moles
6.02 x 1023 molecules
The same conversion factor is used for all elements and compounds

8. Learning Check 1. Convert moles to particles a) 3.0 mole S
b) 45 mole H2O
c) mole CaCO3
2. Convert particles to moles
a) Al atoms
b) x 1023 O2 molecules
c) x 1023 NaCl formula units

9. How do Mass and the Mole relate?
Element
Number of Atoms
Mass of Sample (g)
Hydrogen
6.02 x 1023
1.01
Carbon
12.01
Oxygen
16.00
Sodium
22.99
Aluminum
26.98
Iron
55.85
Even though the number of atoms does not change, the mass of all the atoms does change
Note that the masses of the moles on the table above are the same as atomic mass on the periodic table (coincidence?)
Mole is abbreviated mol (gee, that’s a lot quicker to write, huh?)

10. Molar Mass The Mass of 1 mole (in grams)
Equal to the numerical value of the element’s atomic mass (get from periodic table)
1 mole of C atoms = g
1 mole of Mg atoms = g
1 mole of Cu atoms = g
Also called Atomic Mass, Molecular Mass or Formula Mass
Unit is always expressed as g/mol
Round to hundredths place

11. Learning Check! State the Atomic Mass of each element A. Lithium
B. Bromine
C. Zinc
D. Silver
E. Mercury

12. Molar Mass of Molecules and Compounds
Mass in grams of 1 mole equal numerically to the sum of the atomic masses
1 mole of CaCl2
1 mole Ca x g/mol
+ 2 moles Cl x g/mol = g/mol CaCl2
1 mole of N2O4

13. Learning Check! Find the Molar Masses of the following compounds
A. H2O
B. N2
C. Al(OH)3
D. C6H12O6
E. CaCO3

14. Learning Check
Prozac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass.

15. Mole-Gram Conversion Factors
Grams  Moles
1 mole
molar mass
Moles  Grams

16. Mole-Gram Conversions
How many grams of Al are in 3.00 moles of Al?
3.00 mol Al x g Al = 81.0 g of Al
1 mole Al
How many moles of are in 3.00 g of Calcium?
3.00 g Ca x 1 mole Ca =
40.08 g Ca mol Ca
Molar Masses are taken from the Periodic Table

17. Learning Check!
The artificial sweetener aspartame (Nutra-Sweet) formula C14H18N2O5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame?

18. Mole Road Map

19. Atoms/Molecules and Grams
How many atoms of Cu are present in 35.4 g of Cu?
35.4 g Cu mol Cu X 1023 atoms Cu g Cu mol Cu
= 3.4 X 1023 atoms Cu

20. Atoms/Molecules and Grams (WH)
How many atoms of O are present in 78.1 g of O2?
78.1 g O2 1 mol O X 1023 molecules O2 2 atoms O g O mol O molecule O2

21. Learning Check!
How many atoms of K are present in 78.4 g of K?

22. Learning Check!
What is the mass (in grams) of 1.20 X 1024 molecules of glucose (C6H12O6)?

23. Percent Composition Percent Composition = Mass of the Element x 100%
Mass of the Compound
What is Percent Composition of Hydrogen in Water (H2O)?
Hydrogen x 2 = 2.02
Oxygen x 1 = 16.00
18.02g
% Hydrogen = x 100% = 11.2%
18.02

24. Percent Composition
What is the percent of carbon in C5H8NO4, a compound used to flavor foods and tenderize meats?
a) %C
b) %C
c) %C

25. Chemical Formulas of Compounds (WH)
Formulas give the ratios of atoms or moles of each element in a compound
Always a whole number ratio (the law of definite proportions).
NO2 : 2 atoms of O for every 1 atom of N
1 mole of NO2 : 2 moles of O atoms to every mole of N atoms
If we know the relative number of moles of each element in a compound, we can determine a formula for the compound.

26. Types of Formulas (WH) Empirical Formula
The formula of a compound that expresses the smallest whole number ratio of the atoms present.
Molecular Formula
The formula that states the actual number of each kind of atom found in one molecule of the compound.
Molecular Formula Empirical Formula
C6H12O6 CH2O
C6H6 CH
C4H6Cl2 C2H3Cl

27. Empirical Formula (WH)
1. Determine the mass in grams of each element present, if necessary.
2. Calculate the number of moles of each element.
3. Divide each by the smallest number of moles to obtain the simplest whole number ratio.
If whole numbers are not obtained* in step 3), multiply through by the smallest number that will give all whole numbers
* Be careful! Do not round off numbers prematurely

28. Divide all mole values by smallest (0.167) -
A sample of a brown gas, a major air pollutant, is found to contain 2.34 g N and 5.34g O. Determine the empirical formula for this substance.
N = 2.34g N x 1 mole = moles of N
14.01 g
O = g O x 1 mole = moles of O
16.00 g
Divide all mole values by smallest (0.167) -
N = = 1 O = = 2
Empirical Formula = NO2
(HONORS only)

29. Learning Check
An oxide of Aluminum is formed by the reaction of g of aluminum with g of oxygen. Calculate the empirical formula

30. Empirical Formula from % Composition (WH)
A substance has the following composition by mass: % Na ; % B ; % H
What is the empirical formula of the substance?
Hint: Use sample size of 100 grams. This will contain g of Na, g of B and g of H

31. Molecular Formula Find Empirical Formula
Find Molar Mass of Empirical Formula
Molar Mass of Compound will be given
Divide Mass of Compound = n
Mass of Emp. Formula
Multiply subscripts in Emp. Formula by n to get Molecular Formula

32. Molecular Formula (WH)
A compound has an empirical formula of NO2. The colourless liquid, used in rocket engines has a molar mass of 92.0 g/mole. What is the molecular formula of this substance?
Mass of NO2
N = 1 x =
O= 2 x =
46.01
n = g/mol = 2
46.01 g/mol
Molecular Formula = N2O4

33. Learning Check
A white powder is analyzed and found to have an empirical formula of P2O5. The compound has a molar mass of g. What is the molecular formula?