1. The Mole Concept
Molar Mass, Conversion Problems, Percentage Composition, Empirical Formulas, Molecular Formulas

2. The Mole Chemist’s counting number amount of a substance
1 mole is equal to x 1023 atoms or particles or molecules (Avogadro’s number)
There are always x 1023 particles in one mole of ANY substance
Ex: 1 mole of Carbon atoms = x 1023 atoms

3. Molar Mass Mass of one mole of any substance
Equals the atomic mass on periodic table
Units are g/mol
Examples: C
Mg(OH)2

4. Chemistry equalities
1 mole = grams = x 1023 atoms (cloud these) (Happy mole day )

5. Percentage Composition
Part___ x = Percentage
Whole
Percentage by mass of each element in a compound
Mass of element
Total mass of compound
X 100 = % of the element

6. Example: Which has a higher percentage of Hydrogen? H2O C6H12O6

8. Conversion Factors 1 mole = 6.022 x 1023 1 mole = ~ g
~ g = x 1023
Each of these can be written as a fraction

9. Mole Calculations Uses “standard equalities” to set up a ratio
Special notes **Answer will have same # of significant figures as given value. *** Scientific notation uses the EE button on calculator

10. Common examples:
1. How many eggs in 58 dozen?

11. Example #2 How many moles are in 8.9 grams of Carbon?

12. Example #3: How many grams are in 1.38 x 1023 atoms of gold?

13. Chemistry conversions:
Example #2: How many grams of Lithium are in 3.5 moles?

14. Cancellation Method (Dimensional Analysis)
Conversion factors are a fraction where the top and bottom have equal values
1 foot 16 ounces
12 inches 1 pound
Given units are on the bottom and unknown units are on the top

15. Molecular formula
Actual formula of a compound
Ex: H2O, C6H12O6

16. Empirical Formula
Formula with the lowest whole number ratio of elements
Ex: Write empirical formula of
C6H12O6
N3O9
H2O
C2H6

17. Calculating
List the mass of each element. Assume there is 100 grams if the percentage is given.
Step 1: Convert the grams into moles using the molar mass.
Step 2: Divide by smallest answer
Step 3: To get a whole number ratio
Whole number answers are written as subscripts

18. Example
1. Determine the empirical formula for a compound containing 52% Carbon, 13% Hydrogen, and 35 % Oxygen

19. Determining molecular formula Molecular Formula Atomic Mass Empirical Formula Mass Multiply subscripts of empirical formula by whole number answer.

20. Molecular Formula
1. Determine the molecular formula of the compound with an empirical formula of CH and a formula mass of amu.