THE MOLE

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					THE MOLE
            What is a mole?
• Scientist needed a convenient method to
  accurately count the number of atoms,
  molecules, or formula units

• Since atoms and molecules are so small, it’s
  impossible to actually count them.

• The mole (mol) is the SI unit used to
  measure the amount of a substance
         Avogadro’s number
• A mole is represented by exactly 12g of
  carbon-12

• Through experimentation, a mole was
  established as having 6.02 x 1023 particles

• This number is named after Amedeo
  Avogadro who in 1811 determined the
  volume of one mole of gas.
           Moles to particles
• How many pennies are in three and a half
  dollars

• conversion factor: 100 pennies/1 dollar

• 3.5 dollars x 100 pennies/1 dollar = 350
  pennies
       Moles to Particles Cont’
• How many particles are in 3.5 moles of sucrose


• conversion factor: 6.02 x 1023 particles/1 mol

• 3.5 mol x 6.02 x 1023 molecules sucrose/1 mol =
  2.11 x 1024 molecules of sucrose
          Particles to Moles
• How many moles are is 4.50 x 1024 atoms
  of zinc?

• Conversion factor: 1 mol/6.02 x 1023 atoms

• 4.50 x 1024 x 1 mol zinc/6.02 x 1023 atoms
  zinc = 7.48 mol zinc
             Mole to Mass
• The mass of one mole of any pure substance
  is called its molar mass

• 35 g jellybeans = 1 dozen
  What is the mass of 5 dozen jellybeans

• 5 dozen x 35g jellybeans/1 dozen = 175g
  jellybeans
        Mole to Mass Cont’
• Coversion factor:
  number of moles x number of grams/ 1 mol

• What is the mass of 3 moles of manganese

• 3 mol Mn x 54.9g Mn/1 mol Mn = 165g Mn
         Mass to Molecules
• How many moles of H2O are in 1.00 g of
  H20? How many molecules?

• 1.00 g H2O x 1mol H2O/18.02g H2O =
  0.055g H2O

• 0.055g H2O x 6.02 x 1023molecules H2O
  /1mol H2O = 3.34 x 1022 molecules H2O
        Moles of Compounds
• A molecule of freon, CCl2F2, has 1 carbon
  molecule, 2 chlorine, and 2 fluorine

• 1mol C atoms/1mol CCl2F2

• 2mol Cl atoms/1 mol CCl2F2

• 2mol F atoms/1mol CCl2F2
   Moles of Compounds Cont’
• How many moles of F atoms are in 5.50
  moles of CCl2F2

• 5.50mol CCl2F2 x 2mol F atoms/1mol
  CCl2F2 = 11.0 mol F atoms
    Molar Mass of Compounds
• What is the molar mass of K2CrO4?

• 2 mol K x 39.10g K/1mol K = 78.20g
• 1mol Cr x 52.00g Cr/1mol Cr = 52.00g
• 4mol O x 16.00g O/1mol O = 64.00g

• 78.20g + 52.00g + 64.00g = 194.20g
 Moles of a Compound to Mass
• How many grams of K2CrO4 are in 3.20
  moles of K2CrO4? Molecules?

• 3.20mol K2CrO4 x 194.20g K2CrO4/1mol
  K2CrO4 = 620.8g K2CrO4
        Percent Composition
• Mass of element/mass of compound x 100 =
  percent by mass

• What is the percent by mass of H2O

• 2.02g H/18.02g H2O x 100 = 11.2% H

• 16.00g O/18.02g H2O x 100 = 88.8% O

				
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posted:9/26/2010
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