Transcript The Mole - Independent School District 196

The Mole
What is a mole?
• A conversion factor we use in chemistry to
make it easier to talk about a very large
amount of particles of elements or
compounds
• 1 dozen bagels = 12 bagels
• 1 mole bagels = 6.02 x 1023 bagels
Avogadro’s Number
• Avogadro’s # = 6.02 x 1023 units
• How does this number relate to a mole?
• 1 mole = 6.02 x 1023 units
*Units can be anything but in chemistry these units are
referred to as:
• Particles
• Atoms
• Molecules
• Formula Units
How big is 6.02 x 1023?
• Astronomers estimate that there is a mole of stars in
the Universe.
• One mole of high school textbooks would cover the
USA to a depth of about 300 Km.
• One mole of marshmallows would cover the USA to
a depth of 105 000 Km.
• One mole of moles placed to head to tail would
stretch 11 million light years and weigh 9/10 as
much of the moon.
• One mole of pennies would make at least seven
stacks that would reach the moon.
• One mole of watermelon seeds would be found
inside a melon slightly larger than the moon.
Examples
• 1 mole Fe = 6.02 x 1023 atoms Fe
• 1 mole C12H22O11 = 6.02 x 1023 molecules C12H22O11
• 1 mole Al = 6.02 x 1023 atoms Al
• 1 mole BeF2 = 6.02 x 1023 formula units BeF2
Moles
Particles Conversion
• Remember… 1 mol = 6.02 x 1023 units
• Units in chemistry are atoms, molecules,
formula units, particles
Moles To Particles
• How many atoms of carbon make up 6.80
moles of carbon?
6.80 mol C
6.02 x 1023 atoms C 4.09 x 1024 atoms C
1 mol C
Moles To Particles
• How many formula units of potassium
phosphate make up 1.3 moles?
1.3 mol K3PO4
6.02 x 1023 f.u. K3PO4
1 mol K3PO4
7.8 x 1023 f.u. K3PO4
Moles To Particles
• 2 moles of carbon dioxide = ? molecules
2 mol CO2 6.02 x 1023 molecules
CO2
1 mol CO2
1 x 1024 molecules
CO2
Particles To Moles
How many moles make up 5.60 x 1025 atoms of copper?
5.60 x 1025 atoms Cu
1 mol Cu
6.02 x 1023 atoms Cu
93.0 mol Cu
Particles To Moles
• How many moles make up 6.3 x 1023 formula
units of ammonium nitride?
6.3 x 1025
f.u. (NH4) 3N
1 mol (NH4) 3N
6.02 x 1023
f.u. (NH4) 3N
1.0 x 102 mol (NH4) 3N
Particles To Moles
• 25 molecules of carbon tetrahydride = ? moles
25 molecules CH4
1 mol CH4
6.02 x 1023
molecules CH4
4.2 x 10-23 mol CH4
How is the mole measured in the lab?
• It is impossible to count up individual particles
of chemicals in the lab because of their small
size
• We must find another way to measure 6.02 x
1023 particles of a substance
How does mass relate to the mole?
• What does an amu (atomic mass unit) measure?
1 amu = 1.66053886 × 10-27 kilograms
• A relative scale used to measure the mass of single
elements or compounds
Learning the termonology…
Atomic Mass
• Atomic Mass - measures the mass of a single
atom in amu’s
• Example: 1 atom Fe = 55.85 amu
• *Always go to the hundredths place when
taking measurements from the periodic table
Formula Mass
• Formula Mass - measures the mass of a single
formula unit (ionic compound) in amu’s
• Example: 1 formula unit BeF2 =
1Be 9.01 amu +
2F 2(19.00 amu) = 47.01 amu
Molecular Mass
• Molecular Mass - measures the mass of a
single molecule in amu’s
• Example: 1 molecule C12H22O11 =
12 C atoms 12(12.01 amu) +
22 H atoms 22(1.01 amu) +
11 O atoms 11(16.00 amu) = 342.34 amu
Molar Mass
• The mass of 1 mole of any substance in grams
• Example:
1 atom Fe = 55.85 amu
1 mole (6.02 x 1023 atoms) Fe = 55.85 g
1 molecule C12H22O11 = 342.34 amu
1 mole (6.02 x 1023 molecules) C12H22O11 = 342.34 g
What is a representative particle?
• The smallest particle that represents the
true identity of the entire substance
without altering it’s characteristics or
properties
• Example: What is the representative
particle of 52 Al atoms?
Answer: 1 atom Al
Example: What is the representative particle of
1 molecule of BeF2?
• Answer: 1 molecule BeF2
• 1 atom of Be or 1 atom of F would not truly
represent the properties and characteristics of
BeF2
Moles
Grams Conversion
• Remember… molar mass can be used as a
conversion for any type of particle
12.01 grams C = 1 mole C
58.44 grams of NaCl = 1 mole NaCl
44.01 grams of CO2 = 1 mole CO2
Moles To Grams
• How many grams is 4.672 mol barium
chloride?
1 mol BaCl2 = 208.23 g BaCl2
4.672 mol BaCl2
208.23 g BaCl2
1 mol BaCl2
972.9 g BaCl2
Grams To Moles
• .0025 g disulfur trioxide = ? mol
1 mol S2O3 = 112.14 g S2O3
.0025 g S2O3
1 mol S2O3
112.14 g S2O3
2.2 x 10-5 mol S2O3
Grams
Particles Converting
• This is a 2-step process. You must ALWAYS go
through the mole first.
Grams To Particles
• How many atoms of platinum are needed to
obtain 15.00 g?
195.08 g Pt = 1 mol Pt
1 mol Pt = 6.02 x 1023 atoms Pt
15.00 g Pt
1 mol Pt
6.02 x 1023 atoms Pt
195.08 g Pt
1 mol Pt
4.629x 1022
atoms Pt
Particles To Grams
• What is the mass of 2.77 x 1013 molecules of
oxygen?
32.00 g O2 = 1 mol O2
1 mol O2 = 6.02 x 1023 molecules O2
2.77 x 1013
molecules O2
1 mol O2
32.00 g O2
6.02 x 1023
molecules O2
1 mol O2
1.47 x 10-9 g O2
Liters
Moles Conversion
• Liters (L) are a volume unit of measurement
• STP = standard temperature and pressure
conditions (0°C and 1 atm)
• This conversion only may be used when:
– At STP conditions
– Working with gases
1 mole = 22.4 L of gas @ STP
Liters To Moles
• How many moles of chlorine gas @ STP take
up 4.9 L of space?
4.9 L Cl2
1 mol Cl2
22.4 L Cl2
.22 mol Cl2
Mole To Liters
• How much space does .0359 moles of carbon
monoxide gas take up @ STP?
.0359 mol CO
22.4 L CO
1 mol CO
.804 L CO
Liters
Particles Converting
• This is a 2-step process. You must ALWAYS go
through the mole first.
Liters To Particles
• How many molecules of iodine gas take up
3.56 L of space @ STP?
1 mole = 22.4 L of gas @ STP
1 mole = 6.02 x 1023 particles
3.56 L I2
1 mol I2
6.02 x 1023
molecules I2
22.4 L I2
1 mol I2
9.57 x 1022
molecules I2
Particles To Liters
• How much space does 3.5 x 1022 molecules of
nitrogen dioxide gas take up @ STP?
1 mole = 22.4 L of gas @ STP
1 mole = 6.02 x 1023 particles
3.5 x 1022 molecules
NO2
1 mol NO2
22.4 L
NO2
6.02 x 1023 molecules
NO2
1 mol
NO2
1.3 L
NO2
Liters
Grams Converting
• This is a 2-step process. You must ALWAYS go
through the mole first.
Liters To Grams
• What is the mass of .57 L of hydrogen gas @
STP?
1 mole = 22.4 L of gas @ STP
1 mole = 2.02 g H2
.57 L H2
1 mol H2
2.02 g H2
22.4 L H2
1 mol H2
.051 g H2
Grams To Liters
• How much space does 5 x 105 g of water vapor
take up @ STP?
1 mole = 22.4 L of gas @ STP
1 mole = 18.02 g H2O
5 x 105 g H2O
1 mol H2O
22.4 L H2O
18.02 g H2O
1 mol H2O
6 x 105 L H2O