1. The Mole
1 dozen = 12
1 gross =
144
1 ream =
500
1 mole =
6.02 x 1023

2. I didn’t discover it. Its just named after me!
Avogadro’s Number
6.02 x 1023 is called “Avogadro’s Number” in honor of the Italian chemist Amadeo Avogadro ( ).
I didn’t discover it. Its just named after me!
Amadeo Avogadro

3. Page 291, #3

4. Page 291, #4

5. Calculations with Moles: Using Avogadro’s Number
How many atoms of lithium are in 3.50 moles of
lithium?
3.50 mol Li
6.02 x 1023 atoms Li
= atoms Li
2.11 x 1024
mol Li

6. Page 292, #5

7. Page 292, #6

8. Review: Molar Mass
A substance’s molar mass (molecular weight) is the mass in grams of one mole of the compound.
CO2 = grams per mole
H2O = grams per mole
Ca(OH)2 = g/mol

9. Page 296, #s 7-8
PCl3

10. Calculations with Moles: Converting moles to grams
How many grams of lithium are in 3.50 moles of
lithium?
3.50 mol Li
7.0 g Li
= g Li 25
mol Li

11. Calculations with Moles: Converting grams to moles
How many moles of lithium are in 18.2 grams of
lithium?
18.2 g Li
mol Li
= mol Li
2.6
7.0 g Li

12. Calculations with Moles: Using Avogadro’s Number
How many atoms of lithium are in 18.2 g of
lithium?
18.2 g Li
mol Li
6.02 x 1023 atoms Li
7.0 g Li
mol Li
(18.2)(6.02 x 1023)/7.0
= atoms Li
1.6 x 1024

13. Standard Molar Volume
Equal volumes of all gases at the same temperature and pressure contain the same number of molecules.
- Amedeo Avogadro

14. Standard Molar Volume

15. Standard Temperature and Pressure “STP”
P = 1 atmosphere, kPa
T = 0°C, 273 Kelvins
The molar volume of an ideal gas is 22.4 liters at STP

16. Calculating Percentage Composition
Calculate the percentage composition of magnesium carbonate, MgCO3.
24.0 g g + 3(16.0 g) = 84.0 g
100.00

17. Formulas molecular formula = (empirical formula)n [n = integer]
Empirical formula: the lowest whole number ratio of atoms in a compound.
Molecular formula: the true number of atoms of each element in the formula of a compound.
molecular formula = (empirical formula)n [n = integer]
molecular formula = C6H6 = (CH)6
empirical formula = CH

18. Formulas (continued)
Formulas for ionic compounds are ALWAYS empirical (lowest whole number ratio).
Examples:
NaCl
MgCl2
Al2(SO4)3
K2CO3

19. Formulas (continued)
Formulas for molecular compounds MIGHT be empirical (lowest whole number ratio).
Molecular:
H2O
C6H12O6
C12H22O11
Empirical:
H2O
CH2O
C12H22O11

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

21. Empirical Formula Determination
Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid?

22. Empirical Formula Determination (part 2)
Divide each value of moles by the smallest of the values.
Carbon:
Hydrogen:
Oxygen:

23. Empirical Formula Determination (part 3)
Multiply each number by an integer to obtain all whole numbers.
Carbon: 1.50
Hydrogen: 2.50
Oxygen: 1.00
x 2
x 2
x 2 3 5 2
Empirical formula:
C3H5O2

24. Finding the Molecular Formula
The empirical formula for adipic acid is C3H5O2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid?
1. Find the formula mass of C3H5O2
3(12.0 g) + 5(1.0) + 2(16.0) = 73.0 g

25. Finding the Molecular Formula
The empirical formula for adipic acid is C3H5O2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid?
3. Multiply the empirical formula by this number to get the molecular formula.
3(12.0 g) + 5(1.0) + 2(16.0) = 73.0 g
(C3H5O2) x 2 =
C6H10O4