The Mole

1
The Mole
2
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

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Avogadros Number

• Avogadros 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

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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.

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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

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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

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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

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Learning the termonologyAtomic Mass

• Atomic Mass - measures the mass of a single atom
  in amus
• Example 1 atom Fe 55.85 amu
• Always go to the hundredths place when taking
  measurements from the periodic table

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Formula Mass

• Formula Mass - measures the mass of a single
  formula unit (ionic compound) in amus
• Example 1 formula unit BeF2
• 1Be 9.01 amu
• 2F 2(19.00 amu) 47.01 amu

10
Molecular Mass

• Molecular Mass - measures the mass of a single
  molecule in amus
• 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

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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

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What is a representative particle?

• The smallest particle that represents the true
  identity of the entire substance without altering
  its characteristics or properties
• Example What is the representative particle of
  52 Al atoms?

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• Answer 1 atom Al
• Example What is the representative particle of
  1 molecule of BeF2?

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• Answer 1 molecule BeF2
• 1 atom of Be or 1 atom of F would not truly
  represent the properties and characteristics of
  BeF2