1. Chapter 12: Chemical Quantities
Section 12.1: Counting Particles of Matter

2. The macroscopic vs. the submicroscopic
Is it practical to count out 200 grains of rice, or 200 pieces of macaroni? No Way! We sell these items by the pound. How would we be able to calculate how many items are in a container without counting?

3. Is there a way to know the number without counting?
There is! At your table, discuss a method to figure out how many items are in each bag, without counting. What information would you need?

4. Counting by Weighing Mass of the empty jar (with stopper) = 209.624 g
How many candy hearts are in the jar?
What you need; the data:
Mass of the empty jar (with stopper) = g
Mass of the full jar (with stopper)= g
Average mass of one candy heart= 1.92 g

5. Counting by Weighing (cont)
How many atoms are in g of Hydrogen if the average mass of
one atom is x g?
What you need:
Total mass
Mass of one atom
What number do you get?
6.02 x 1023 atoms of H

6. STOICHIOMETRY
The study of the relationships between the macroscopic quantities like mass and volume, and the submicroscopic quantities like number and mass of the atoms involved in a chemical reaction.
Chemists cannot count individual items because the particles of matter are too small and too numerous- so we use this process.

7. What is a mole?
The group or unit of measure that we use in chemistry to count numbers of atoms, ions, molecules or formulas units of a substance (elements or compounds)
Mole Map U
g&list=PLKEmXepzBsY9Zx4EHN27HHSQyvb4Xysb 4&index=6

8. What is Avogadro’s Number?
6.02 x 1023
This HUGE quantity represents the number of particles in one mole of ANY substance. It is just a number!
A mole can be analogous to a dozen, a pair, a century…you know how many individual parts there are in each one of these measurements, right?
12, 2, 100…a mole is just A LOT more.
Video

9. The mass in grams of one mole of an element or a compound! (g/mol)
What is Molar Mass?
The mass in grams of one mole of an element or a compound! (g/mol)
For elements, it is the atomic mass in grams
One atom of magnesium = u (atomic mass units )
One mole of magnesium = g/mol
For compounds, it is the sum of all the masses of each element in the compound’s formula
One mole
MgSO4 = (16.0) = g/mol

10. So what about molecular mass and formula mass?
These are not hard to calculate, because essentially the value of each is the same. It is the units that are different!
Formula Mass is a term used for IONIC compounds
NaCl has a FORMULA mass of u and a MOLAR mass of g/mol
~ Same quantity, different unit
Ex. CaCl2
Ca: 1 x 40.1 = 40.1
Cl: 2 x 35.5 = 71
Formula mass = u
Molar mass = g/ mol

11. So what about molecular mass and formula mass? (Cont)
Molecular Mass is a term used for COVALENT compounds
C2H6 has a MOLECULAR mass of 30.1 u and a MOLAR mass of 30.1 g/mol
Ex: C2H6O
C: 2 x 12 = 24
H: 6 x 1 = 6
O: 1 x 16 = 16
Molecular mass = 46 u
Molar mass = 46 g/ mol

12. When solving problems like the following, you must use DIMENSIONAL ANALYSIS (Factor Label Method).
Steps
grams ↔ moles ↔ “stuff”
Molar mass Avogadros #

13. Practice Problems (pg 410)
68 g NH3 = ? mol
1 N = 1 x = g
3 H = 3 x = g
= g NH3
68 g NH3 x 1 mole NH3 = mol NH3
g NH3

14. Practice Problems (cont)
17.5 g CuO = ? mol
1 Cu = 1 x = g
1 O = 1 x = g
= g CuO
17.5 g CuO x 1 mole CuO = mol CuO
g CuO

15. Practice Problems (cont)
0.550 mol F2 = ? g
2 F = 2 x = g
 0.550 mol F2 x g F2 = g F2
1 mole F2

16. Practice Problems (cont)
2.35 mol BaI2 = ? g 1 Ba = 1 x = g 2 I = 2 x = g = g 2.35 mol BaI2 x g BaI2 = g BaI2 1 mole BaI2

17. Practice Problems (cont)
10.7 g Li = ? atoms
10.7 g Li x 1 mole Li X x 1023 atoms Li
6.941 g Li mole Li
= 9.28 x 1023 atoms Li

18. Practice Problems (cont)
144.6 g W = ? atoms
144.6 g W x 1 mole W X x 1023 atoms W
g W mole W
= 4.73 x 1023 atoms W

19. Practice Problems (cont)
1. Does 50.0 g S or 50.0 g Sn represent a greater # of atoms?
50.0 g S x 1 mole S X x 1023 atoms S
g S mole S
= x 1023 atoms S
50.0 g Sn x 1 mole Sn X x 1023 atoms Sn
g Sn mole Sn
= 2.54 x 1023 atoms Sn
Sulfur is smaller- has a greater number of atoms

20. What mass of water must be weighed to obtain 7.50 mol of H2O
How many moles are in 17.5g copper (II) oxide
How many molecules are in each sample?
89g nitrogen monoxide
10.8g boron trifluoride
What is the molecular mass of aspirin (C9H8O4)