1. Chapter 6
Chemical Composition

2. Counting by Weighing Counting is time consuming Weighing is fast
If we know average mass, we can count by weighing

3. Counting by Weighing
Plain M&Ms

4. Counting by Weighing
Peanut M&Ms

5. Lab 1 Lab 2 Lab 3 Lab 4 Lab 5 Lab 6 Lab 7 Lab 8 Calc Plain M&Ms
Actual Plain M&Ms
Calc Peanut M&M
Actual Peanut M&Ms
Calc Mini M&Ms
Actual Mini M&Ms
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5
Lab 6
Lab 7
Lab 8

6. Atom are small Really small Gold
Atomic Force Microscope (AFM) that can simultaneously map surface topography and measure the "dragging" or frictional force of the tip as it scans across a surface.

7. Atomic Masses: Counting by Weighing
Atomic Mass Units  amu
Only used for atoms
Very Small!!
1 amu = 1.66 x g
Mass number units on periodic table:
amu
1 atom

8. Atomic Masses: Counting by Weighing
We need a reasonable number to weigh atoms
Avogadro ( )
Avogadro's Hypothesis: equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.
He also proposed that oxygen gas and hydrogen gas were diatomic molecules.

9. The Mole 
Avogadro’s Number
6.022 x 10 23

10. Mole Facts
6.02 X 1023  Watermelon Seeds: Would be found inside a melon slightly larger than the moon.
6.02 X 1023  Donut Holes: Would cover the earth and be 5 miles (8 km) deep.
6.02 X 1023  Pennies: Would make at least 7 stacks that would reach the moon.

11. Mole Facts
6.02 X 1023  Grains of Sand: Would be more than all of the sand on Miami Beach.
6.02 X 1023  Blood Cells: Would be more than the total number of blood cells found in every human on earth.
6.02 X 1023  C02 Molecules: Would be found in 1 Mole Balloon TM at STP.
1 Liter bottle of Water contains 55.5 moles H20

12. Mole Facts 5 Pound Bag of Sugar contains 6.6 moles of C12H22O11
1 Mole BalloonTM: Contains 22.4 Liters of any gas at STP.
There are 3 types of moles that live underground in North America: Eastern Mole, Hairy-Tailed Mole and Star-Nosed Mole
The "Mexican" Mole: Is a chocolate sauce or turkey stew. It comes from the Aztec word "molli." For recipes go to Web Hangouts.

13. grams  moles  molecules

14. Molar Mass A chemical compound is a collection of atoms
Molar mass is the mass in grams of one mole of a chemical compound
To find molar mass, add up the masses of all the atoms

15. Figure 6.3: Various numbers of methane molecules.

16. Molar Mass of Sulfur dioxide
Sulfur dioxide = SO2
1 mole SO2  1 mole S atoms
 2 moles O atoms
1 mole S atoms = 1 X g = g
2 moles O atoms = 2 X g = g
1 mole SO2 molecules = g/mol
Don’t round molar mass

17. Molar Mass of PVC PVC is polyvinyl chloride, C2H3Cl
What is the mass of 1 mole C2H3Cl?
2 mol C atoms = 2 x = g
3 mol H atoms = 3 x = g
1 mol Cl atoms = 1 x = g
= g/mol
Don’t round molar mass

18. Calculate Molar Mass Sodium nitride, Na3N Carbon disulfide , CS2
Ammonium bromide, NH4Br
Ethyl alcohol, C2H5OH
82.98 g/mol Na3N
76.15 g/mol CS2
g/mol NH4Br
g/mol C2H5OH

19. Calculating Mass from Moles
What is the mass of 4.86 mol of CaCO3?
Molar Mass of CaCO3?
1 mol Ca = 1 x g = g
1 mol C = 1 x g = g
3 mol O = 3 x g = g
Molar mass of CaCO3 = g/mol

20. Calculating Mass from Moles
Molar mass of CaCO3 = g
What is the mass of 4.86 mol of CaCO3?
4.86 mol CaCO3 x g = ?
mol
= 486 g CaCO3

21. Moles from Mass How many moles is 1.56 g of juglone?
Juglone is a dye used for centuries that produced from black walnut trees. It is also a natural herbicide.
Formula = C10H6O3
Find Molar Mass of juglone
174.1 g/mole

22. Moles from Mass 1mol = 174.1 g of juglone
1.56 g juglone x 1 mol juglone =?
174.1 g
mol juglone
8.96 x 10-3 mol juglone

24. Percent Composition of Compounds
Percent by mass
Percent = x 100%
Mass fraction
of a given =
element
Part
Whole
Mass of element present in 1 mol of compound
Mass of 1 mol of compound

25. Percent by Mass of Each Element in PVC, C2H3Cl
2 mol C atoms = 2 x = g
3 mol H atoms = 3 x = g
1 mol Cl atoms = 1 x = g
= g/mol
% C = x 100% = % C
% H = x 100% = % H
% Cl = x 100% = % Cl
24.02 g
62.494g
3.024 g
62.494g
35.45 g
62.494g
% Total to check

26. grams  moles  molecules

27. Percent by Mass Price E.L. Fudge original $3.09 24 Famous Amos Vanilla
Number of Cookies/Package
E.L. Fudge original
$3.09 24
Famous Amos Vanilla
$2.59 45
Dunksters Double Crème
$2.99 38
Value Time Peanut Butter
$2.09 54

28. Mole Day, March 20, 2008
Celebrated annually on October 23 from 6:02 a.m. to 6:02 p.m., Mole Day commemorates Avogadro's Number (6.02 x 1023), which is a basic measuring unit in chemistry. For second term, we are celebrating on March 20th.
Mole Day was created as a way to foster interest in chemistry. Schools throughout the United States and around the world celebrate Mole Day with various activities related to chemistry and/or moles.

29. Mole Day, March 20, 2008
For a given molecule, one mole is a mass (in grams) whose number is equal to the atomic mass of the molecule. For example, the water molecule has an atomic mass of 18, therefore one mole of water weighs 18 grams. An atom of neon has an atomic mass of 20, therefore one mole of neon weighs 20 grams.
In general, one mole of any substance contains Avogadro's Number of molecules or atoms of that substance. This relationship was first discovered by Amedeo Avogadro ( ) and he received credit for this after his death.

30. Extra Credit Mole Day Projects
 Make Mole Day treats to share:
Moleasses cookies, Avogadro Dip, Mole Cake, Guacamole or Taco-mole sauce
Make an object of “mole” art
Create a “Moletin” Board or poster
Write a Mole Day poem or song to perform for the class
Create a “Mole-opoly” game
Create mole day flag or costume
Create a mole day T-shirt (5-points maximum)
Make a mole piñata or a stuffed mole

31. Extra Credit Mole Day Projects
0 to 20 points extra credit are possible. Points given will be based on effort and creativity and added to your homework grade.
You may do more than one project BUT you may receive a maximum of 20 points.
There is no make-up or late projects allowed.

32. grams  moles  molecules

33. Figure 6.5: Ball-and-stick model of P4O10.

34. Empirical Formula of a Compound
Converting masses measured in laboratory to chemical formulas
Need to convert gram to moles and then develop an empirical formula
Empirical Formula – the formula of a compound that expresses the smallest whole-number ratio of the atoms present.
Molecular Formula – the actual formula of the compound.

35. Determining the Empirical Formula of a Compound (p. 179)
Step 1 - Obtain the mass of each element
Consider g of the compound.
33.88% Cu = g Cu
14.94% N = g N
51.18% O = g O

36. Determining the Empirical Formula of a Compound (p. 179)
Step 2 - Determine the number of moles of each element
33.88 g Cu x = mol Cu
14.94 g N x = mol N
51.18 g O x = mol O
1 mole
63.55 g
1 mole
14.01 g
1 mole
16.00 g

37. Determining the Empirical Formula of a Compound (p. 179)
Step 3 - Divide the number of moles of each element by the smallest number of moles to convert the smallest number to

38. Determining the Empirical Formula of a Compound (p. 179)
Step 3 continued - If all the number are integers (whole numbers), they are the subscripts in the empirical formula.
If one or more of these numbers are not integers, go to Step 4.
The empirical formula is CuN2O6
[i.e., Cu(NO3)2]

39. Determining the Empirical Formula of a Compound (p. 179)
Step 4 – Multiply the numbers you derived in step 3 by the smallest number that will convert all of them to whole numbers. This set of numbers represents the subscripts in the empirical formula.

40. Empirical Formula of a Compound
C6H12O6 = CH2O
C6H6 = CH
Na2O2 = NaO