The Mole

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The Mole
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The Mole (Mol)

• Is a Number
• Represents an amount of particles of a compound
• 6.022 x 1023
• Called Avogadros Number
• Units can be particles, atoms, molecules or
  formula units
• You can have a mole of anything

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Converting between moles and particles

• 1 mole 6.022 x 1023 particles
• 1 mole
• 6.022 x 1023particles is a conversion factor
• How many moles are in 4.5 x 1030 atoms of Fe?
• 4.5 x 1030 atoms Fe x 1 mole
• 6.022 x 1023 atoms

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Converting between moles and particles

• How many atoms of Na are there in 1.34 moles of
  Na?
• 1.34 moles x 6.022 x 1023 particles
• 1 mole

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Practice

• Determine the number of Zn atoms in 2.50 moles of
  Zn.
• Calculate the number of molecules in 11.5 moles
  of water.
• How many moles make up 5.75 x 1024 atoms of Al?
• How many moles of CO2 are in 3.75 x 1024
  molecules of CO2?

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The Mole and Mass

• The mole represents 6.022 x 1023 particles of
  anything
• Those particles have masses
• Therefore the Mole can be related to a mass of
  6.022 x 1023 particles.
• This is called the molar mass (the mass of 1 mole
  of a substance)
• Molar mass vary with each substance

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Molar Masses for elements

• The molar mass of an element is the atomic mass
  on the periodic table followed by grams
• Carbons atomic mass is 12.011
• The mass of 6.022 x 1023 atoms of carbon (1 mole)
  12.011 grams

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Molar Mass of Compounds

• The molar mass of a compound is the sum of all
  the atoms masses that make up the compound
• NaCl Na (23 grams) Cl (35 grams)
  58 grams

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Converting Using Molar Mass

• 1 mole
• Molar mass
• Determine the mass of 3.57 moles of Al
• 3.57 moles Al x 27 g Al
• 1 mole Al

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Converting Using Molar Mass

• Determine the number of moles found in 25.5 g of
  Ag.
• 25.5 g Ag x 1 mole Ag
• 108 g Ag

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Practice

• Determine the mass of 42.6 mol of Si
• Determine the mass of 3.45 x 102 mol Co
• Determine the mass of 2.45 x 10-2 mol Zn
• Determine the number of moles in 300.0 g S
• Determine the number of moles in
• 1.25 x 103 g Zn
• Determine the number of moles in 1.00 kg Fe

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Empirical Formulas

• The simplest ratio of atoms found in a compound
  is called the empirical formula.
• Can be calculated by knowing a compounds percent
  composition.

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Percent Composition

• Percent by mass () Molar mass of element x 100
• Molar mass of the compound

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Calculating Composition

• Compound is peroxide H2O2
• Find the mass of each element (if there is more
  than one atom of an element, the mass must be
  multiplied by the subscript)
• 2 x H 2 x 1.0 g ? 2 g
• 2 x O 2 x 16.0 g ? 32g
• Find the Total Mass 34 g

• H 2 g x 100 5.9 H
• 34g
• O 32 g x 100 94.1 O
• 34 g
• To check your answer make sure the add up to
  100

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Practice

• Calculate the percent composition of each element
  in the compound Calcium sulfate.
• Calculate the percent of potassium in KCl
• Calculate the percent composition of the compound
  diphosphorus pentoxide.
• Calculate the percent composition of carbon
  dioxide

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Determining Empirical Formulas

• Drop all signs and add (g) unit
• Convert all grams to moles using the elements
  molar mass.
• Divide all mole amounts by the smallest mole
• As long as the number is a whole number it now
  becomes that elements subscript
• Special rounding is sometimes necessary
• If the decimal is .25 multiply by 4
• If the decimal is .33 multiply by 3
• If the decimal is .5 multiply by 2
• This creates a whole number

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Practice

• Methyl Acetate is a solvent commonly used in some
  paints, inks, and adhesives. Determine the
  empirical formula for methyl acetate, which has
  the following chemical analysis 48.64 C 8.16
  H and
• 43.20 O.

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Practice

• Determine the empirical formula for a compound
  that contains 35.98 Aluminum and 64.02 sulfur.