1. Chemical Composition
Chapter 8

2. Nutrasweet Aspartic acid Analysis
Qualitative -- what elements -- C, H, N, & O.
Quantitative -- how many of each element --C4H7NO4.

3. Counting Atoms Atoms are too small to be seen or counted individually.
Atoms can only be counted by weighing them.
all jelly beans are not identical.
jelly beans have an average mass of 5 g.
How could 1000 jelly beans be counted?

4. Jelly Beans & Mints Mints have an average mass of 15 g.
How would you count out 1000 mints?
Why do 1000 mints have a mass greater than 1000 jelly beans?

5. Atomic Mass Unit
Atoms are so tiny that the gram is much too large to be practical.
The mass of a single carbon atom is 1.99
x g.
The atomic mass unit (amu) is used for atoms and molecules.

6. AMU’s and Grams 1 amu = 1.661 x 10 -24 g Conversion Factors
1.661 x 10-24g/amu
6.022 x 1023amu/g

7. Calculating Mass Using AMU’S
1 N atom = amu
(23 N atoms)(14.01 amu/1N atom) = amu

8. Calculating Number of Atoms from Mass
1 O atom = amu
(288 amu)(1 O atom/16.00 amu) = 18 atoms O

9. Atomic Masses Elements occur in nature as mixtures of isotopes
Carbon = 98.89% 12C
1.11% 13C
<0.01% 14C
Carbon atomic mass = amu

10. AMU’s & Grams 1 atom C = 12.011 amu = 1.99 x 10-23g 1 mol C = 12.011 g
Use TI-83 or TI-83 Plus to store x 1023 to A.

11. Measurements dozen = 12 gross = 12 dozen = 144 ream = 500
mole = x 1023

12. The Mole
The number equal to the number of carbon atoms in exactly 12 grams of pure 12C.
1 mole of anything =  1023 units of
that thing
Equal moles of substances have equal numbers of atoms, molecules, ions, formula units, etc.

13. Figure 8.1 (a): All these sample of pure elements contain the same number (a mole) of atoms: x 1023 atoms
Pb – 207.2g
Cu – 63.55g
Ag – 107.9g

14. How many atoms does each substance contain?
Figure 8.2: One-mole samples of iron (nails), iodine crystals, liquid mercury, and powdered sulfur
How many atoms does each substance contain?

15. The Mole Substance Average Atomic Mass # Moles # Atoms (g)
Na x 1023
Cu x 1023
S x 1023
Al x 1023

16. Avogadro’s number equals 6.022  1023 units

17. The Mole
One mole of rice grains is more than the number of grains of all rice grown since the beginning of time!
A mole of marshmallows would cover the U.S. to a depth of 600 miles!
A mole of hockey pucks would be equal in mass to the moon.

18. Unit Cancellation How many dozen eggs would 36 eggs be?
(36 eggs)(1 dozen eggs/12 eggs) = 3 dozen eggs
How many eggs in 5 dozen?
(5 dozen eggs)(12 eggs/1 dozen eggs) = 60 eggs

19. Calculating Moles & Number of Atoms
1 mol Co = g
(5.00 x 1020 atoms Co)(1mol/6.022 x 1023 atoms)
= 8.30 x 10-4 mol Co
(8.30 x 10-4 mol)(58.93g/1 mol) = g Co
Moles are the doorway
grams <---> moles <---> atoms

20. Molar Mass
A substance’s molar mass is the mass in grams of one mole of the compound.
CO2 = grams per mole
1 C = 1 ( g) = g
2 O = 2 ( g) = g
44.01 g

21. Calculating Mass from Moles
CaCO3
1 Ca = 1 (40.08 g) = g
1 C = 1 (12.01 g) = g
3 O = 3 (16.00 g) = g g
(4.86 molCaCO3)( g/1 mol) = 486 g CaCO3

22. Calculating Moles from Mass
Juglone
10 C = 10(12.01g) = g
6 H = 6(1.008 g) = g
O = 3(16.00 g) = g g
(1.56 g juglone)(1 mol/174.1 g) = mol juglone

23. Percent Composition Mass percent of an element:
For iron in iron (III) oxide, (Fe2O3)

24. % Composition CuSO4. 5 H2O 1 Cu = 1 (63.55 g) = 63.55 g
1 S = 1 (32.06 g) = g
4 O = 4 (16.00 g) = g
5 H2O = 5 (18.02 g) = g g

25. % Composition (Continued)
% Cu = g/249.71g (100 %) = % Cu
% S = g/ g (100 %) = % S
% O = g/ g (100 %) = % O
% H2O = g/ g (100 %) = % H2O
Check: Total percentages. Should be equal to 100 %
plus or minus 0.01 %.

26. Formulas molecular formula = (empirical formula)x
[x = integer]
molecular formula = C6H6 = (CH)6
empirical formula = CH

27. Formulas Ionic compounds -- empirical formula NaCl CaCl2
Covalent compounds -- molecular formula -
C6H12O6
C2H6

28. Empirical Formula Determination
1. Base calculation on 100 grams of compound.
2. Determine moles of each element in 100 grams of compound.
3. Divide each value of moles by the smallest of the values.
4. Multiply each number by an integer to obtain all whole numbers.

29. Calculating Empirical Formulas
63.68 % C, % N, 9.80 % H, & % O
(63.68 g C)(1 mol/12.01g) = mol C/.8837 mol = 6
(12.38 g N)(1 mol/14.01g) = mol N/.8837 mol = 1
(9.80 g H)(1 mol/1.01 g) = 9.70 mol H/.8837 mol = 11
(14.14 g O)(1 mol/16.00g) = mol O/.8837 mol = 1
C6NH11O

30. Calculating Empirical Formulas
4.151 g Al & g O
(4.151 g Al)(1 mol/26.98 g) = mol Al/ mol = 1.000
(3.692 g O)(1 mol/16.00 g) = mol O/ mol = 1.500
1 Al (2) = 2 Al
1.5 O (2) = 3 O
Al2O3

31. Molecular Formulas 71.65 % Cl, 24.27 % C, & 4.07 % H
(71.65g Cl)(1 mol/35.45g) = mol/2.021 mol = 1
(24.27 g C)(1 mol/12.01g) = mol/2.021 mol = 1
(4.07 g H )(1 mol/1.01g) = mol/2.021 mol = 2
(EM)x = (MM)
(49.46)x = (98.96)
x = 2
(EF)x = (MF)
(ClCH2)2 = Cl2C2H4