Download 1 mole SO 2

Tuesday, April 5th: “A” Day
Wednesday, April 6th: “B” Day
Agenda
PSAE Practice Test #3
Begin Chapter 7: “The Mole and Chemical
Composition”
In-Class Assignments:
Practice pg. 228: #1-4
Practice pg. 229: #1-4
Concept Review: “Avogadro’s
Number and Molar Conversions”: #1-5
Begin Section 7.1:
“Avogadro’s Number and Molar
Conversions”
Atoms, ions, and molecules are very small, so
even tiny samples have huge numbers of
particles.
Scientists use the mole to make counting such
large numbers easier.
Mole: the SI unit for amount; the number of
atoms in exactly 12 grams of carbon-12.
Avogadro’s Number & the Mole
The number of particles in a mole is called
Avogadro’s Number.
Avogadro’s number is 6.022  1023; the number
of atoms or molecules in 1 mole
The Mole is a Counting Unit
The mole is used to count out a given number of
particles, whether they are atoms, molecules,
formula units, ions, or electrons.
The mole is just one kind of counting unit:
1 dozen = 12 objects
1 roll = 50 pennies
 1 hour = 3,600 seconds
1 pair = 2
 1 mole = 6.022  1023 particles

Conversion Factors
The definition of one mole is:
6.022  1023 particles = 1 mol
Using this definition, we get 2 conversion factors:
6.022 X 1023 particles = 1
1 mol
_____1 mol________ = 1
6.022 X 1023 particles
Choose the Conversion Factor that
Cancels the Known Units
 **Because a conversion factor is equal to 1, it
can multiply any quantity without changing
the value. Only the units are changed. **
When solving conversion problems, the unit
that you’re trying to get rid of goes on the
bottom of the fraction.
Converting Between Amount in Moles
and Number of Particles
Sample Problem A, pg 228
Converting Between Amount in Moles to Number of
Particles
Find the number of molecules in 2.5 mol of sulfur
dioxide, SO2.
 Known: 2.5 moles of SO2
 Unknown: # of molecules of SO2
 Conversion factor: 6.022 X 1023 molecules SO2
1 mole SO2
Start with what you know, mult. by conversion factor:
 2.5 mol SO2 X 6.022 X 1023 molecules SO2 = 1.5 X1024
1 mole SO2
molecules
SO2
Additional Practice
How many particles are there in 2.45 X 10-6 mol of nickel,
Ni (II) selenide, NiSe?
 Known: 2.45 X 10-6 moles NiSe
 Unknown: # of particles of NiSe
 Conversion factor: 6.022 X 1023 particles NiSe
1 mol NiSe
Start with what you know, mult. by conversion factor:
 2.45 X 10 -6 mol NiSe X 6.022 X 1023 particles NiSe =
1 mole NiSe
1.48 X 1018 particles
NiSe
We can go the other way too and
convert number of particles to
amount in moles…
Sample Problem B, pg. 229
Converting Number of Particles to Amount in Moles
A sample contains 3.01 X 1023 molecules of sulfur
dioxide, SO2. Determine the amount in moles.
 Known: 3.01 X 1023 molecules of SO2
 Unknown: moles of SO2
 Conversion factor: ____1 mole SO2_____
6.022 X 1023 molecules SO2
Start with what you know, mult. by conversion factor:
 3.01 X 1023 molecules SO2 X __1 mole SO2______
6.022 X 1023 molecules SO2
= 0.500 moles SO2
Additional Practice
How many moles are equivalent to 7.95 X 1024 copper (II)
chloride, CuCl2, formula units?
 Known: 7.95 X 1024 CuCl2 formula units
 Unknown: # of moles of CuCl2 formula units
 Conversion factor: _____1 mole CuCl2__
6.022 X 1023 formula units CuCl2
Start with what you know, mult. by conversion factor:
 7.95 X 1024 form. unit CuCl2 X ____1 mole_CuCl2___
6.022 X 1023 form. unit CuCl2
= 13.2 mol CuCl2
In-Class Assignments
You must SHOW WORK!
Practice pg. 228: #1-4
Practice pg. 229: #1-4
Concept Review: Avogadro’s Number and
Molar Conversions”: #1-5