Today's Agenda .m 11/08/10

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Today's Agenda .th 11/18/10

• Recall Have your Comp/Notebooks ready
• Percent Compositions
• Empirical Formula
• Hydrates

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Lab TomorrowWebsite is updated
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Recall

• Find the of moles of
• 1 g of Carbon dioxide CO2
• 1 g of Carbon monoxide CO
• Find the mass (in g) of
• 1 mole Hydrogen chloride HCl
• 1 mole Potassium nitrate KNO3Hint Find the
  Molar Mass of all Compounds

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Empirical Formula

• Empirical Formula shows the simplest ratio of a
  compound.
• Example H2OThis shows the simplest ratio of a
  compound
• Non-Example H4O2This is still water and a
  chemical formula, but its not an empirical
  formula because its not in simplest ratio form.

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Empirical Formula Examples

• Write the following chemical formulas in
  Empirical formula form.
• C6H16O2
• Na4S2O8
• Mn4O6

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Percentage Composition
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• Often times, you will be given a percent
  composition of a substance without knowing the
  compound.
• This means you have to find the Empirical Formula.

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Percentage Composition
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• Example

• Find the Empirical Formula of
• C 60.0
• H 13.4
• O 26.6
• Find C?H?O?

• Assume that you have 100g of each
• C 60.0 x 100g 60.0 g
• H 13.4 x 100g 13.4 g
• O 26.6 x 100g 26.6 g

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Percentage Composition
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• Now find the Molar Mass of each element

• Molar mass C 12.01 g/mol
• Molar mass H 1.01 g/mol
• Molar mass O 16.00 g/mo

• Calculate the amount of moles for each element

• of moles C C
• of moles H H
• of moles O O

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Percentage Composition
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• At this point you can write a chemical formula
  like this

C5H13.3O1.66

• But you need to get the Empirical Formula because
  this is not the simplest form

• Now you take the smallest number 1.66 and
  divide each number by 1.66

C
H
O
C3H8O1
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Hydrates

• Hydrates are anything that has water in it.
• Hydrates are a way to say or show how much water
  is in something
• Example
• Cesium Carbonite Dihydrate
• Cs2CO2 2H2O
• Example
• Cobalt (II) Chloride hexahydrate
• CoCl2 6H2O

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Common Prefixes

• Hydrate H2O
• di- 2H2O
• tri- 3H2O
• tetra- 4H2O
• penta- 5H2O
• hexa- 6H2O
• hepa- 7H2O
• octa- 8H2O

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Homework
44444

• Do the four problems on the mini handout in your
  comp/notebook.
• These problems are also on page 243 in your text
  book and on-line
• This and the notes will count as a stamp for
  tomorrow.