Chemical Quantities AKA The Mole

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Chemical QuantitiesAKA The Mole
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What is a Mole?

• A mole is a way to count atoms.
• The word mole is used to
• describe a specific number of
• things. Just like the definition of
• a dozen is the quantity 12, the
• mole has a quantity of
• 6.02 x 1023 abbreviated (mol).
• Just like a dozen the mole can be
• used for any object. In
• chemistry we use it most often to
• count the numbers of atoms, ions, and molecules.

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Why the Mole?

• A mole is a way to count
• atoms. It is to say the least
• impractical to try to count the
• numbers of atoms, molecules,
• or ions. The mole is named
• for Amedeo Avagadro.
• Avagadro clarified the difference
• between atoms and molecules,
• he did not calculate the mole.

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Representative Particles

• The importance of naming and
• writing correct formulas is very
• important for determining moles.
• When given a substance you
• have to know what makes it up
• i.e. ions, molecules, or atoms.
• Not only will you be asked to find
• the moles of a compound, you
• will also have to find the atoms
• of that compound.

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Molar Mass (gram atomic mass)

• When working with chemicals our
• most common measurement is
• the gram. The atomic mass can
• be expressed as the amount in
• grams of a mole of an element.
• For example the atomic mass of
• oxygen is 15.99 amu. There is
• 15.99 grams of oxygen in one
• mole and 6.02x1023 atoms in
• 15.99 grams of oxygen.

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Molar Mass (gram molecular mass)

• When working with
• compounds we often need to
• know the moles of molecules
• present. To find this simply
• add the atomic masses of the
• elements in the compound.
• This number in grams is the
• amount needed to get 6.02x1023.

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Molar Mass (gram formula mass)

• When working with ionic
• compounds it is important to
• realize that the representative
• particle is a formula unit and not
• a molecule. It is still figured the
• same way we just have
• to be sure and get the formula
• units correct. For example
• calcium sulfide CaS is correctly
• written Ca2S2 will give you the
• wrong values for a mole
• of calcium sulfide.

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