Monday 43007 Aday

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Monday 4/30/07A-day

• Reaction Stoichiometry (Ch 12)

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Paper work

• Stuff to collect

• Stuff to distribute

• nothing

• nothing

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Homework

• Monday nothing
• Tuesday Flowchart in Class ActivityCut out the
  pieces at home and bring them to class in an
  envelopedont lose any.
• Wednesday Exam Flowchart (Optional)
• Thursday
• Friday Bring your books for in-class reading
  assignment. (GRSW 14)

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The Exam

• 1-period
• Multiple choice problem solving
• 3 problems
• 40 total MC questions (A-E)
• 100 points
• You may use the Flowchart if you choose to
  complete it. The Flowchart will be graded.

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Objectives for CH 12

• Define stoichiometry and distinguish between
  composition and reaction stoichiometry.
• Identify the major types of reaction
  stoichiometry problems.
• Perform mol-mol, mol-volume, mol-mass, mass-mol,
  mass-volume, and mass-mass stoichiometric
  calculations given ideal conditions.
• Identify the limiting reactant in a chemical
  reaction.
• Perform mol-mol, mol-volume, mol-mass, mass-mol,
  mass-volume, and mass-mass stoichiometric
  calculations using a limiting reactant.
• Perform calculations involving the percent yield
  of a chemical reaction.

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Composition vs. Reaction Stoichiometry

• Composition Stoichiometry deals only with mass
  relationships with in a compound.
• Reaction Stoichiometry deals with mass
  relationships in chemical reactions.

Mol Ratio
Reactant (Given)
Product (Find)
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General Factor-Label

• All vol-vol stoichiometry problems will follow
  this pattern.
• It is identical to mol-mol problemsthe only
  difference is that volume units are used instead
  of moles.
• The critical conversion factor is the vol ratio.
• Remember Molar Volume _at_ STP 1 mol 22.4 L of
  any gass
• Molar volume can be used to relate mass or moles
  to volume at STP.

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General Factor-Label

• All mol-volume stoichiometry problems will follow
  this pattern.
• The critical conversion factors are the mol ratio
  and the molar volume.

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General Factor-label

• Mass to volume problems are a combination of all
  of the previous types.
• All mass-volume stoichiometry problems will
  follow this pattern.
• The critical conversion factors are the mol
  ratio, the molar volume, and the molar mass of
  the Given.

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Volume Stoichiometry Examples

• How many liters of ammonia can be generated from
  4 L of hydrogen reacting with excess nitrogen?
• Given 4.0 L H2
• Find L NH3
• Equation
• 3H2 N2 ? 2NH3
• 3L H2 2 L NH3
• Solution
• Answer The reaction of 4.0 L of hydrogen with
  excess nitrogen can produce 2.7 L of ammonia.

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Volume Stoichiometry Examples

• How many liters of carbon dioxide at STP can be
  consumed by 250 g of lithium hydroxide?
• Given 250 g LiOH
• Find L CO2
• Equation
• CO2 2LiOH ? Li2CO3
  H2O
• 1mol CO2 2 mol LiOH
• 23.94834 g/mol
• 1 mol 22.4 L _at_ STP
• Solution
• Answer The reaction of 250 g of lithium
  hydroxide will consume 120 L of carbon dioxide.

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Visual Concepts

• What is reaction stoichiometry?
• What is a mole ratio?
• What is a mass to mole reaction stoichiometry
  problem?
• What is a mass to mass reaction stoichiometry
  problem?
• What is a limiting reactant?
• What is the difference between actual yield and
  theoretical yield?

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Percent Yield

• part / whole X 100
• The part
• actual yield (given in the problem)
• The whole
• Theoretical yield (from stoichiometry calculation)

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Yield Example Problem

• In the commercial production of the element
  arsenic, arsenic(III) oxide is heated with
  carbon, which reduces the oxide to the metal
  according to the following equation
• 2As2O3 3C ? 3CO2 4As
• If 8.87 g of As2O3 is used in the reaction and
  5.33 g of As is produced, what is the percentage
  yield?

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Yield Example

• Given 8.87 g As2O3 used 5.33 g As produced
• Find L CO2
• Equation
• 2As2O3 3C ? 3CO2 4As
• 2 mol As2O3 4 mol As
• 197.8414 g/mol 74.9216 g/mol
• yield (actual yield theoretical yield)100
• Solution

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Yield Example

• Solution
• Answer The percent yield for this reaction is
  79.3.

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Whiteboard

• 2 people per team
• If we have extra people, then we go to groups of
  3.
• Your performance is being graded.
• At the end of the week the average score will be
  assigned a 90 grade.
• The more problems that you solve the more points
  you will get.