The Mole

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The Mole
2
Standards
Students know the quantity one mole is set by defining one mole of carbon 12 atoms to have a mass of exactly 12 grams.
Students know one mole equals 6.02 x 1023 particles (atoms or molecules).
Students know how to determine the molar mass of a molecule from its chemical formula and a table of atomic masses and how to convert the mass of a molecular substance to moles, number of particles, or volume of gas at standard temperature and pressure.
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The Mole
1 dozen
12
1 gross
144
1 ream
500
1 mole
6.02 x 1023
There are exactly 12 grams of carbon-12 in one
mole of carbon-12.
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Avogadros Number
6.02 x 1023 is called Avogadros Number in
honor of the Italian chemist Amadeo Avogadro
(1776-1855).
I didnt discover it. Its just named after me!
Amadeo Avogadro
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Calculations with MolesConverting moles to grams
How many grams of lithium are in 3.50 moles of
lithium?
3.50 mol Li
6.9 g Li
g Li
45.1
1 mol Li
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Calculations with MolesConverting grams to moles
How many moles of lithium are in 18.2 grams of
lithium?
18.2 g Li
1 mol Li
2.62
mol Li
6.94 g Li
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Calculations with MolesUsing Avogadros Number
How many atoms of lithium are in 3.50 moles of
lithium?
3.50 mol
6.02 x 1023 atoms
atoms
2.07 x 1024
1 mol
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Calculations with MolesUsing Avogadros Number
How many atoms of lithium are in 18.2 g of
lithium?
18.2 g Li
1 mol Li
6.02 x 1023 atoms Li
6.9 g Li
1 mol Li
atoms Li
1.58 x 1024
(18.2)(6.02 x 1023)/6.9
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Calculating Formula Mass
Calculate the formula mass of carbon dioxide, CO2.
12.0 g 2(16.0 g)
44.0 g
? One mole of CO2 (6.02 x 1023 molecules) has a
mass of 44.0 grams
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Standard Molar Volume
Equal volumes of all gases at the same
temperature and pressure contain the same number
of molecules. - Amedeo Avogadro
At STP (Standard Temperature and Pressure) 1
mole of a gas occupies 22.4 liters of volume
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The Mole Highway
6.02x1023 Rep Part
Form Mass
1 mol
22.4 L
1 mol
1 mol
x
x
x
x
x
x
1 mol
Form Mass
1 mol
22.4 L
6.02x1023 Rep Part
1 mol
Mass (g)
Rep Part
Vol (L)
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Calculations with Moles
Two-Step Problem
How many atoms of lithium are in 18.2 g of
lithium?
18.2 g Li
1 mol Li
6.02 x 1023 atoms Li
6.9 g Li
1 mol Li
atoms Li
1.58 x 1024
(18.2)(6.02 x 1023)/6.9
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Calculating Percentage Composition
Calculate the percentage composition of magnesium
carbonate, MgCO3.
From previous slide 24.3 g 12.0 g
3(16.0 g) 84.3 g
100.00
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Formulas
Empirical formula the lowest whole number ratio
of atoms in a compound.
Molecular formula the true number of atoms of
each element in the formula of a compound.

• molecular formula (empirical formula)n n
  integer
• molecular formula C6H6 (CH)6
• empirical formula CH

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Formulas (continued)
Formulas for ionic compounds are ALWAYS empirical
(lowest whole number ratio).
Examples
NaCl
MgCl2
Al2(SO4)3
K2CO3
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Formulas (continued)
Formulas for molecular compounds MIGHT be
empirical (lowest whole number ratio).
Molecular
C6H12O6
C12H22O11
H2O
H2O
Empirical
CH2O
C12H22O11
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Empirical Formula DeterminationRules

1. Base calculation on 100 grams of compound.
2. Determine moles of each element in 100 grams of
   compound.
3. Divide each value of moles by the smallest of the
   values.
4. Multiply each number by an integer to obtain all
   whole numbers.

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Empirical Formula DeterminationExample
Adipic acid contains 49.32 C, 43.84 O, and
6.85 H by mass. What is the empirical formula of
adipic acid?
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Empirical Formula Determination(part 2)

Divide each value of moles by the smallest of the
values.
Carbon
Hydrogen
Oxygen
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Empirical Formula Determination(part 3)
Multiply each number by an integer to obtain all
whole numbers.
Carbon 1.50
Hydrogen 2.50
Oxygen 1.00
x 2
x 2
x 2
3
5
2
C3H5O2
Empirical formula
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Finding the Molecular Formula
The empirical formula for adipic acid is C3H5O2.
The molecular mass of adipic acid is 146 g/mol.
What is the molecular formula of adipic acid?
1. Find the formula mass of C3H5O2
3(12.0 g) 5(1.0) 2(16.0) 73.0 g
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Finding the Molecular Formula(continued)
2. Divide the molecular mass by the mass given by
the empirical formula.
3(12.0 g) 5(1.0) 2(16.0) 73.0 g
3. Multiply the empirical formula by this
number to get the molecular formula.
(C3H5O2) x 2
C6H10O4