Click on the picture to take you to

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Click on the picture to take you to the limiting
reagent animation
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Large legos are 26.4 grams / dozen Medium
legos are 14.0 grams / dozen Small legos are
9.4 grams / dozen
The bag of large legos weighs 335.8
grams The bag of medium sized legos weighs
213.8 grams The bag
of small legos weighs 169.7 grams
lego "molecule"

• Which lego size will run out first?
• How many lego molecules can be formed?
• How many legos of the other two sizes will be
  unused?

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Large legos are 26.4 grams / dozen Medium
legos are 14.0 grams / dozen Small legos are
9.4 grams / dozen
The large bag weighs 335.8 grams The medium
bag of legos weighs 213.8 grams The small bag
weighs 169.7 grams
Which lego size will run out first?
lego "molecule"
335.8 g x 1 dozen 12.5 dozen large
26.4 g
213.8 g x 1 dozen 15.3 dozen medium
14.0 g
This will run out first!
169.7 g x 1 dozen 18 dozen small
9.4 g
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2
2
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Large legos are 26.4 grams / dozen Medium
legos are 14.0 grams / dozen Small legos are
9.4 grams / dozen
The large bag weighs 335.8 grams The medium
bag of legos weighs 213.8 grams The small bag
weighs 169.7 grams
How many lego molecules can be formed?
lego "molecule"
335.8 g x 1 dozen 12.5 dozen large
26.4 g
213.8 g x 1 dozen 15.3 dozen medium
14.0 g
169.7 g x 1 dozen 18 dozen small
9.4 g
equals 75 molecules
12.5 dozen large x 1 dozen lego molecules
6.25 dozen lego molecules
2 dozen large legos
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Large legos are 26.4 grams / dozen Medium
legos are 14.0 grams / dozen Small legos are
9.4 grams / dozen
The large bag weighs 335.8 grams The medium
bag of legos weighs 213.8 grams The small bag
weighs 169.7 grams
lego "molecule"
335.8 g x 1 dozen 12.5 dozen large
26.4 g
213.8 g x 1 dozen 15.3 dozen medium
14.0 g
169.7 g x 1 dozen 18 dozen small
9.4 g
equals 33.6 medium
6.25 dozen x 2 medium legos 12.5 mediums
used 1 lego molecule
15.3 total 12.5 used 2.8 dozen mediums extra.
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Large legos are 26.4 grams / dozen Medium
legos are 14.0 grams / dozen Small legos are
9.4 grams / dozen
The large bag weighs 335.8 grams The medium
bag of legos weighs 213.8 grams The small bag
weighs 169.7 grams
lego "molecule"
335.8 g x 1 dozen 12.5 dozen large
26.4 g
213.8 g x 1 dozen 15.3 dozen large
14.0 g
169.7 g x 1 dozen 18 dozen large
9.4 g
equals 66 small
6.25 dozen x 2 small legos 12.5 small legos
used 1 lego molecule
18 total 12.5 used 5.5 dozen small extra.
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2Na(s) Cl2 ? 2NaCl
Which reagent will run out first? This one will
limit the total amount of NaCl product.
Na
Cl
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http//www.scientia.org/cadonline/Chemistry/stoich
iometry/limitreagm.ASP
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2Na(s) Cl2 ? 2NaCl
If you have 2 moles of Na and 2 moles of
Cl2, Which reagent (chemical on the left of the
equation) will run out first?
Answer 2 moles of Na will react with exactly 1
mole of Cl2. Therefore, the Na will run out first
leaving half of the Cl2 left over and unreacted.
Na is called the limiting reagent
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4 Fe(s) 3O2(g) ? 2Fe2O3(s)
If I have 7 moles of Fe and 4 moles of O2, how
many moles of Fe2O3 can be made?
The ratio is 4 Fe to 3O2 Therefore a ratio could
be set up to show which reagent will run out
first
continued
7 x 3 / 4 5.25 moles O2 reacts with 7 moles of
Fe. Since we have only 4 moles O2 it is the
limiting reagent
4 Fe 3 O2 7 Fe ? O2
each coefficient x 1.75
(7 Fe(s) 5.25 O2(g) ? 3.5 Fe2O3)
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4 Fe(s) 3 O2(g) ? 2 Fe2O3
Therefore 4 mole O2 x 2 moles Fe2O3 2.66
moles Fe2O3 produced 3
moles O2
The amount of Fe left over can also be
calculated 2.66 moles Fe2O3 x 4 moles Fe
5.33 moles of Fe are used
2 moles Fe2O3
Since I began with 7 moles of Fe and used 5.33
moles I have 7 - 5.33 1.67 moles of
excess Fe left over
This can be converted to grams also if needed
1.67 moles x 55.8 g Fe 93.18 g Fe

1 mole
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http//www.chemcollective.org/applets/stoich.php
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Which type of paper will be the limiting
reagent (which will run out first)? How many
folders can be created? How many copies of each
type of paper will be left over and unused?
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What will limit the total of packets?
87 copies Title page x 1packet of materials
87 packets
1 title page
83 copies instruction page x 1packet of
materials 83 packets
1 instruction page
82 packets possible
168 copies data sheets x 1packet of materials
84 packets
2 data sheets
The number of sheets of graph paper will limit
the number of packets.
328 sheets graph paper x 1packet of materials
82 packets
4 sheets of graph paper
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What will limit the total of packets?
82 packets x means 5 extra title sheets

82 packets means 1 extra instruction sheet

82 packets x 2 data sheets 164 copies of
data sheet USED 168 164 4 extra
1 packet

82 packets x 4 sheets graph paper 328 pieces
of graph paper USED 1
packet
328 - 328 NO EXTRA graph paper
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http//cwx.prenhall.com/petrucci/medialib/media_po
rtfolio/text_images/ 015_LIMITREAGENT.MOV
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http//www.chem.iastate.edu/group/Greenbowe/sectio
ns/projectfolder/ flashfiles/stoichiometry/stoic_s
elect_both.html
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Great link below to lots of chemistry
animations Click below
http//www.chemanimationsindex.iastate.edu/group/G
reenbowe/sections/ projectfolder/animationsindex.h
tm
another good link
http//www.mhhe.com/physsci/chemistry/essentialche
mistry/flash/flash.mhtml