1. The Mole Concept Introduction Number of Particles and Moles Topic 1.2

3. Dimensional Analysis
starting with one unit of measurement and ending up with a different one
“cancel out” what you don’t want
use conversion factors (fraction that equals one)
the numerator will contain the unit you want
the denominator will contain the unit you are trying to get rid of
try to predict a “ball park answer” if possible so you might recognize a wrong answer

5. sometimes they can be done in one step
example: 23,532 seconds = ? minutes
23,532 sec. X 1 min.
sec.
min.

6. sometimes they take multiple steps
example: 23,532 seconds = ? hours
23,532 sec. X 1 min. X 1 hour =
sec min.
hours

7. but if you don’t know the conversion factor(s), the problem becomes impossible
example: 750 ml = ? fl oz
750 ml X 1 fl oz ml
25.3 fl oz

8. How many minutes are in 2.5 hours?
Initial unit
2.5 hr
Conversion Final
factor unit
2.5 hr x min = min
1 hr
cancel Answer (2 SF)
LecturePLUS Timberlake

9. How many seconds are in 1.4 days?
What is wrong with the following setup?
1.4 day x 1 day x min x 60 sec
24 hr hr min

10. How many seconds are in 1.4 days?
1.4 day x 1 day x min x 60 sec
24 hr hr min
Units would be = day2(sec)/hr2
Not the final unit needed

11. Topic 1.2 really starts here

12. Measuring Matter By counting By determining the mass
simply a number or moles
By determining the mass
grams
By determining the volume
liters

13. Not these!
The Mole
Not this!

14. known as Avogadro’s number
the mole is a unit used in chemistry to represent a large number of particles such as…
atoms (Ne, Ar…)
molecules (H2O, CO2…)
ionic compounds (NaCl, MgCl2…)
ions (Mg2+, Cl1-…)
similar to a dozen, except instead of 12, it’s 602 billion trillion
6.02 x or 602,214,199,000,000,000,000,000
known as Avogadro’s number

15. 1 dozen cookies = 12 cookies
1 mole of cookies = 6.02 X 1023 cookies
1 dozen cars = 12 cars
1 mole of cars = 6.02 X 1023 cars
1 dozen Al atoms = 12 Al atoms
1 mole of Al atoms = 6.02 X 1023 atoms
Note that the NUMBER is always the same, but the MASS would be very different!
Mole is abbreviated mol (gee, that’s a lot quicker to write, huh?)

16. 1 mole C 1 mole water 1 mole NaCl 6.02 x 1023 C atoms
6.02 x 1023 H2O molecules
1 mole NaCl
6.02 x 1023 NaCl ionic compounds (formula units)
6.02 x 1023 Na+ ions
6.02 x 1023 Cl– ions

17. Note that a particle could be an atom OR a compound OR a molecule!
for counting in chemistry, the conversion factor will be:
1 mole
6.02 x 1023 particles OR

18. Number of particles to moles
How many moles in 5.68 x 1025 fluorine molecules?
5.68 x 1025 F2 molecules x _____1 mole____
x 1023 molecules
= mol F2

19. How many moles of water in 7.77x1024 molecules of water?
7.77 x 1024 molecules H2O x mole
6.02x1023 molecules
= 12.9 moles H2O

20. Number of moles to particles
How many atoms in 5.59 moles of He?
5.59 moles He x x 1023 atoms
mole
= x 1024 atoms
How many atoms in 2.98 moles of H20 molecules?
2.98 moles x 6.02 x 1023 molecules H2O x atoms
mole molecule H2O
= 5.38 x atoms