Transcript The Mole - Tommasini

The Mole
Mass & The Mole
Ch. 10.1-10.2
CHM Hon.
How do you measure matter?
• Measure the amount by:
– Counting
– Mass
– Volume
Measuring Matter
• Different forms of measurement relate
– 1 dozen apples = 12 apples
– 2.0 kg apples = 1 dozen apples
– 1 dozen apples = 0.2 bushel apples
Finding Mass from a Count
• What is the mass of 9 averagesized apples if 1 dozen apples
has the mass of 2.0 kg?
• 15 kg
Finding Mass from a Count
• If 0.20 bushel is 1 dozen apples and
a dozen apples has a mass of 2.0
kg, what is the mass of 0.5 bushel of
apples?
• 5.0 kg
What is a mole?
• Remember: Matter is composed of atoms,
molecules and ions
• Mole (mol)
– 6.02 x 1023 representative particles of that
substance
– The SI Unit for measuring the amount of a
substance
What is a mole?
• Avogadro’s number
– The number of representative particles in a
mole
– 6.02 x 1023
– Avogadro (1776-1856): Italian scientist who
helped clarify the difference between atoms
and molecules
The Representative Particle
• Refers to the species present in a substance
– Usually atoms, molecules or formula units
– The representative particle of most elements is the
atom
– Sometimes the representative particle is a molecule
ex) Molecular compounds (H2O)
• 7 elements normally exist as diatomic molecules
– H2, N2, O2, F2, Cl2, Br2, I2
The Representative Particle
– A mole of any substance contains
Avogadro’s number of representative
particles (6.02 x 1023)
Converting Number of Particles to
Moles
• 1 mol = 6.02 x 1023 representative particles
• Conversion Factor:
Converting Number of Particles to
Moles
Converting Number of Particles to
Moles
• 0.208 mol Mg
How many moles is 2.8 x 1024
atoms of silicon?
• 4.65 mol Si
Converting Moles to Number of
Atoms
• 1.40 x 1025 atoms
amu
• Remember that atomic mass of an
element (the mass of a single atom) is
expressed in atomic mass units!
– Relative values based on C-12 atom
• C-12 atom = Mass 12 amu
• H atom = Mass 1 amu
Atomic mass & Molar mass
• Molar mass = the mass of a mole of an element
• The Atomic mass of am element expressed in grams
is the mass of a mole of the element
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Carbon: molar mass = 12 g
Hydrogen: molar mass = 1 g
32.1 g
Sulfur: molar mass = ?
Mercury: molar mass = ? 200.6 g
Molar mass is the mass of 1 mol
of atoms of any element!!
Magnesium (Mg):
1 mol Mg  6.02 x 1023 atoms Mg Molar mass 24.3 g
Determining the Mass of a Mole of
a Compound
• First step: determine the molecular
formula
– Ex) Sulfur trioxide:
• Second step: calculate the mass of the
molecule
– Add the atomic masses of the atoms
Finding the Molar Mass of a
Compound
34.0 g
Finding the Molar Mass of a
Compound
Find the molar mass of PCl3
106.5 g
Mole to Mole conversion
13.1 mol Ca
Determine the number of moles in
25.5 g Ag
0.236 mol Ag
Mass to Atoms Conversion
How many atoms are in 55.2 g Li?
4.79 x 10 24 atoms Li
Atoms to mass Conversion
0.366 g He
What is the mass in grams of
6.02x1024 atoms Bi
2.09 x 103 g Bi
I am so confused!?
Putting it into prospective…
MASS  MOLES  REP. PARTICLES