Download Chapter 10.1

Chapter 10.1
The Mole: A Measurement of
Matter
► Three
ways of measuring things…count,
mass, & volume.
► Examples: soda—6 pack
►
soda—liter
►
grapes--lbs
► Terms
for specific counts…pair, dozen, etc.
► 1 dozen apples = 12 apples.
► 1 dozen apples = 2.0 kg apples.
► 1 dozen apples = 0.2 bushels apples.
► Ratios: 1 dozen apples/12 apples
► 1 dozen apples/2.0 kg apples
► 1 dozen apples/0.2 bushels apples
Problem…
► What
is the mass of 90 apples if 1 dozen
apples = 2.0 kg?
► Analyze…known…
►#
of apples = 90
► 12 apples = 1 dozen
► 1 dozen = 2.0 kg
► Unknown…mass of 90 apples = ?kg
Calculate
Evaluate
► Does
it make sense?
► Practice…What is the mass of 0.5 bushels of
apples?
► Practice…assume
8 seeds per apple. How
many seeds are in 14 kg of apples?
What is a Mole?
►A
specified number of particles. Used by
chemists. 6.02 x 1023 representative
particles (Avagrado’s number).
► Representative particles can be atoms,
molecules, or formula units.
► Ratio: 1 mole/6.02x1023 rep. particles
Scientific basis of the mole
► 6.02x1023
is the number of atoms in 12
grams of Carbon-12.
► If one mole of carbon-12 atoms were
weighed, it would weigh exactly 12 grams.
Atoms to moles
► How
many moles in 1.25x1023 atoms of
magnesium?
► Known; # of atoms = 1.25x1023
► 1 mole = 6.02x1023 atoms Mg.
► Unknown; moles of magnesium.
► Calculate…
Moles to # of particles
► How
many atoms in a mole? First
determine how many atoms in a
representative particle.
► How many atoms in 2.12 moles of propane
(C3H8)?
► Known: # of moles of C3H8 is 2.12. 1 mole
= 6.02x1023 molecules C3H8. 1 molecule
C3H8 = 11 atoms.
► Unknown: # of atoms.
► Calculate…
► Practice…
many atoms in 1.14 moles SO3?
► How many moles in 4.65x1024 molecules
NO2?
► How
The Mass of a Mole of an Element
► Mass
of atoms expressed in amu’s (atomic
mass units), which are relative units based
on the isotope Carbon-12 (12.0 amu).
► C-12 is twelve times heavier than an
average hydrogen atom with a mass of 1.0
amu.
► 100 C-12 atoms are 12 times heavier than
100 hydrogen atoms.
► Any
number of C-12 atoms are always
twelve times heavier than the same number
of hydrogen atoms.
► The
mass ratio of 12 carbon atoms to 1
hydrogen atom is the same regardless of
the units used to express the mass.
► Therefore,
12.0 g of carbon atoms and
1.0 g of hydrogen atoms must have the
same number of atoms.
Representative Particle
►
►
1.
2.
3.
4.
Smallest unit in a substance
Can be different things
One atom (metals, atomic substances)
One molecule (molecular compounds)
One ion (charged atoms or molecules)
One formula unit (ionic compounds)
Examples of Representative
particles
Substance
Representative
particle
Iron
atom
Atomic nitrogen atom
Nitrogen gas
molecule
water
molecule
Calcium ion
ion
Calcium fluoride Formula unit
glucose
molecule
Formula
Fe
N
N2
H2O
Ca2+
CaF2
C6H12O6
Measuring Chemical Substances
► Using
Avogadro’s number: a specific number
of representative particles
6.02 x 1023 RP/mole
► Referred
to as one mole (mol)
Example: One mol water contains
► 6.02 x 1023 H20 molecules
Example: one mole nitrogen gas…
Practice
Q: how many moles does 1.25 x 1023 atoms of Mg represent?
A: 1.25 x 1023 Mg atoms x (6.03 x 1023 RP)/mole =
0.2 moles
Q: how many moles does 2.8 x 1024 atoms of silicon have?
A: 2.8 x 1024 Si atoms/6.03 x 1023 RP/mole =
4.6 moles
Q:Q: How many propane (C3H8) molecules are in 2.12 mol of
C3H8 ?
A: 2.12 moles x (6.03 x 1023 ) RP/mole = 12.8
Converting molecular Moles into
Number of individual atoms
Hint: when asked for # of atoms always do
Moles
#molecules
#atoms
Practice
Q: How many atoms are in 2.12 mol of C3H8 ?
► First calculate how many molecules
A: 2.12 moles x (6.02 x 1023 RP)/mole= 12.76 x 1023 RP =
1.28 x 1024 RP
► Then calculate how many atoms
Each RP (C3H8) has 11 atoms/RP
Multiply with 11: 1.28 x 1024 RP x 11 Atoms/Rp=
14.08 X 1024 atoms
► Clean all results to single digit number!!!
14.08 X 1024 → Atoms = 1.4 x 1025 atoms
Practice
You have 4.65 x 1024 molecules of NO2?
Q: How many atoms?
A: RP NO2 has three atoms/molecule
3 atoms/molecule x 4.65 x 1024 molecules
The mass of one mole of a given
element
► Mass
of an element is indicated in the
periodic table as the mass number
► Called amu = atomic mass unit
► amu is the mass (in grams) of one mole of
this element
► Remember it is an average number of the
different isotopes…it has decimals
Finding mass
► What
is the mass of one mole O, P, K, S33, 146C
► Atomic oxygen: 16.00 g/mole
► Atomic phosphorus: 30.97 g/mole
► Atomic potassium: 39.10 g/mole
► Atomic S-33: 33.00 g/mole
► Atomic 146C: 14.00 g/mole
How many mole in a given mass
► How
many moles of Carbon are found in 52
g?
► 52 g/12.01 g/mole C= 4.33 moles C
Practice calculating molar masses
Q: How many moles of C-14 are found in 34 g?
► 34 g x mole C-14/14g C-14 = 2.42 moles C-14
Q: What mass does 6.02 x 1023 atoms of Hydrogen
have?
► Is one mole → 1.01 g
Q: What is the mass of 2.34 x 1022 atoms of
phosphorus? First find how many moles
2.34 x 1022 atoms x mole/6.02 x 1023 atoms = 0.04
moles P
0.04 moles P x 30.97 g/mole = 1.24 g
Mass of a Mole of a Compound
► Example:
SO3
► What type of compound?
► How many atoms of S and O?
► Add up amus of S and O
► 32.1 amu + 16.0 amu +16.0 amu + 16.0
amu = 80.1 amu
► One mole SO3 weighs 80.1 g
Practice: find the molar masses
Find the molar mass of
► Water
► Glucose
► Carbon dioxide
Practice
Q:How many moles of glucose are in 200 g?
► Molar mass of glucose is 180.18 g/mole
A: 200g x mole/180.18 g = 1.11 moles
Q: How many molecules of glucose is this?
6.02 x1023 RP/mole x 1.11 moles = 6.7 x 10 23
molecules glucose