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Stoichiometry Concept Presentation - Adele Strazar

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Stoichiometry Concept Presentation - Adele Strazar
Adele Strazar
The following components are mixed in with
the detailed lesson sequence:
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Objective
Lesson
Assessment and Evaluation
Misconceptions/difficulties
Demo
Practical/societal applications/implications
Annotated resources
D1. analyse processes in the home, the workplace, and the
environmental sector that use chemical quantities and
calculations, and assess the importance of quantitative
accuracy in industrial chemical processes;
D2. investigate quantitative relationships in chemical reactions,
and solve related problems;
D3. demonstrate an understanding of the mole concept and its
significance to the quantitative analysis of chemical reactions.
D1.1 analyse processes in the home, the workplace,
and the environmental sector that involve the use of
chemical quantities and calculations (e.g., mixing
household cleaning solutions, calculating
chemotherapy doses, monitoring pollen counts) [AI, C]
Sample issue: Health care professionals are expected
to calculate dosages of prescription drugs accurately
and safely. This requires precision in applying
fractions, decimals, ratios, percentages, and metric
conversions. Despite the care taken by health care
professionals, improper medication use by patients
accounts for about 30% of hospital emergency
department visits.
Sample questions: Why is baking powder used in
cake batter? What happens when too much or too
little of that ingredient is used? Why might two people
on the same drug regimen not necessarily take the
same dosage to treat the same illness? How are carbon
dioxide emissions calculated and why are they
monitored?
D1.2 assess, on the basis of research, the importance of
quantitative accuracy in industrial chemical processes
and the potential impact on the environment if
quantitative accuracy is not observed [IP, PR, AI, C]
Sample issue: Errors in quantitative accuracy have
played a role in many industrial chemical disasters
worldwide. Failing to adjust the quantities of chemicals
needed to produce different batch sizes of a product
have created runaway reactions, resulting in huge
explosions. Such industrial accidents can have
devastating short and long-term effects on the
environment.
Sample questions: Why is it important to use the
correct salt-sand mix on highways during winter
storms? Why is it important to correctly measure the
chemicals used in water treatment plants? How might
incorrect measurements affect the environment? How
and why are environmental contaminants monitored in
soil, water, and air around a chemical manufacturing
plant?
D2.1 use appropriate terminology related to
quantities in chemical reactions, including,
but not limited to: stoichiometry, percentage
yield, limiting reagent, mole, and atomic mass
[C]
D2.3 solve problems related to quantities in
chemical reactions by performing calculations
involving quantities in moles, number of
particles, and atomic mass [AI]
D2.5 calculate the corresponding mass, or
quantity in moles or molecules, for any given
reactant or product in a balanced chemical
equation as well as for any other reactant or
product in the chemical reaction [AI]
D2.6 solve problems related to quantities in
chemical reactions by performing calculations
involving percentage yield and limiting reagents
[AI]
D2.7 conduct an inquiry to determine the actual
yield, theoretical yield, and percentage yield of
the products of a chemical reaction.... assess the
effectiveness of the procedure, and suggest
sources of experimental error [PR, AI]
D3.4 explain the quantitative relationships
expressed in a balanced chemical equation,
using appropriate units of measure (e.g., moles,
grams, atoms, ions, molecules)
Stoichiometry
Concept Summary
Use conversions between
moles and grams when
asked to determine the
amount of products we
will obtain from a certain
quantity of reactants in a
chemical equation or vice
versa.

Mole ratios are used to
determine the
quantities of one or
more substances
involved in the
reaction.
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The ratio is found from
the coefficients in a
balanced chemical
equation.
http://www.hcc.mnscu.edu/chem/V.13/page_id_2062.html
Stoichiometry
Concept Summary
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Three basic steps to
solving
stoichiometry
problems:
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Change what you are
given into moles.
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Use a mole ratio
based on the
coefficients in the
balanced chemical
reaction.
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Change to the units
needed for the
answer.
http://www.rapidlearningcenter.c
om/chemistry/college_chemistry/
balancing-equations.html
http://courses.moodleshare.c
om/course/view.php?id=69
http://s-owl.cengage.com/ebooks/vining_owlbook_prototype/ebook/ch3/Sect3-3-c.html
Stoichiometry
Concept Summary

The limiting reactant is
consumed completely
in a reaction.
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The theoretical yield is
the amount of produce
that can be formed
from a given amount of
limiting reactant. The
actual yield is the
amount of product
collected from
experimental data.

Percentage yield is a
measure of the
efficiency of a reaction.
It is the actual yield
divided by the
theoretical yield,
multiplied by 100.
http://www.chem.tamu.edu/class/majors/tutorialnotefiles/limiting.htm
http://courses.moodleshare.com/mod/resource/view.php?id=2972
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LESSON 1 Defining Stoichiometry
LESSON 2 Stoichiometry Calculations
LESSON 3 Stoichiometry Lab Prep
LESSON 4 Stoichiometry Lab
LESSON 5 Solve Stoichiometry Problems
LESSON 6 Stoichiometry Web Site Review
LESSON 7 Limiting Reactants and Percent Yield
LESSON 8 Limiting/Excess Reactants and Percent Yield Lab
LESSON 9 Reactions with Different Mole Ratios Lab
LESSON 10 Mixed Reception
Objectives

Define stoichiometry.
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Relate and compare stoichiometry to
balancing chemical equations.
 Determine mole ratios using the
balanced chemical equation.
 Solve stoichiometry problems
involving mass, volume and particles
using the mole diagram.
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Describe, citing examples, how
stoichiometry affects personal and publicpolicy decision-making.
Catalytic converter in a car
http://www.quickhonda.net/exhaust.htm
Lesson
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Demo: Reactive substances and correlation with quantities
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Ask four students to add 5.0ml water to an empty film canister. Have them
break up a sodium bicarbonate tablet into four unequal pieces (small,
medium, medium-large, large). Students put the piece of sodium
bicarbonate on the lid of the film canister. On the teacher’s mark, the
students snap on the lid, invert the canister, and back way from the table.
The film canisters will pop and launch into the air. Discussion correlates to
the size of the tablet.
Law of Conservation of Matter
 Write the equation for photosynthesis on the board.
Verify that matter and mass are conserved on both sides
of the equation with hands-on models.

PEOE (Predict, Explain, Observe, Explain) Demo: React KMnO4
with NaHSO3
 Students draw PEOE charts on group whiteboard. Class
discussion of how one of the reactants is completely used up
and the other is in excess.

Review rules for balancing equations.
 Focus lesson lecture. Students take notes.
 Think-pair-share for a group discussion.

Explain what stoichiometry is and importance
 Discuss stoichiometry in manufacturing, medicine, geologists
(test for CaCO3), space (CO2 scrubbers), air bag inflation,
catalytic converters, etc.
 Real world example with Smores activity.
devacaf.caes.uga.edu/main/lessonPlan/SMoreLP.pdf
Assessment
 Smores lab worksheet to be handed in at the beginning of the next class.

Assign an STSE project for the stoichiometry unit. Use the curriculum
documents in SCH3U D1.1 and D1.2 for topic ideas of how stoichiometry
is present in the real world. Students may choose a performance-based
assessment from the following website: http://www.emtech.net/Alternative_Assessment.html
Misconceptions
 Law of Conservation of Matter: The masses, numbers and types of
atoms are the same on both sides of a balanced equation. In all types of
reactions the atoms involved are rearranged to form new substances.

Use pictures and video examples to show the law
Objectives
 List the sequence of steps used in solving stoichiometric problems.

Solve stoichiometric problems where moles are given.
Lesson
 Focus lesson lecture on mole-mole and mole-mass stoichiometric
problems. Students take notes.
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Watch the Stoichiometry Roadmap. http://screencast.com/t/ZmIwMjMwMzkt

Students work in groups of four to answer the first question. One
student from each group is chosen by a lottery system to write the
group’s answer on the board. The teacher writes a numerical mark beside
each group’s answer and asks the students to make their answers
correct. When the questions are all correct, the class moves onto the
next question on the sheet.
Assessment
 Remaining questions are for homework. Both worksheets handed in at beginning of the
next class period.
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http://www.gpb.org/files/pdfs/gpbclassroom/chemistry/moleMoleProblemsWkst.pdf
http://www.gpb.org/files/pdfs/gpbclassroom/chemistry/moleMassProblemsWkst.pdf
Misconceptions
 One mole of compound always contains one more of each element present in the
compound.
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Substances always react in a 1:1 ratio.
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Review the definition of the mol through discussion and encourage students to watch
educational videos on YouTube as a study resource (eg. Khan Academy).
Practice finding the molar ratio using a speed round activity. (Each of the students stand, and
may only sit once they have answered correctly.)
Assume the chemical formula represents the mass ratio of individual elements, or the
ratio of molar masses of elements.
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Review the definition of molar mass, having the class collaboratively use calculations involving
molar mass.
Objective
 Using background knowledge on stoichiometry, students design a
titration lab experiment to determine molar ratios in a chemical reaction.
Lesson
 Demo: Teacher demo’s a titration using the Virtual Chem Lab website:
http://www.chemcollective.org/vlab/vlab.php
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Pre-lab prep
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Arrange students in groups of four.
Students will be given the following during the lab: 1 M NaOH, 1 M HCL, 1 M H2SO4, 2 burets,
beaker, pH indicator
Students design an experiment to calculate the molar ratio of NaOH to HCl, and NaOH to
H2SO4.
Students verify the procedure with the teacher by the end of class, to ensure they are on the
right track. Teacher ensures that lab safety measures are included in the procedure.
Assessment
 Students hand in an individual copy of the procedure at the beginning of
the next class period.
Misconceptions
 Lab safety precautions do not need to be written in the lab procedures,
because they already know in their minds how to avoid hazards.
 Reinforce that someone else must be able to read your procedure and it is not
ethical to set a person up for running into unexpected safety hazards.
Objective
 Using background knowledge on stoichiometry,
students design a titration lab experiment to
calculate molar ratios in a chemical reaction.

Analyze and summarize lab result in a lab report.
Lesson
 Student groups perform the lab experiments
they designed. Instructor answers questions,
redirects groups, and ensures lab safety.
http://www.dartmouth.edu/~che
mlab/techniques/titration.html
Assessment
 Rubric: Observe student performance during lab.
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Lab reports due at the beginning of the next class period. Lab report
includes:
 Introduction, conclusions (balanced equations), procedure, discussion (what might
be done differently next time, liked/disliked about the lab).
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Exit ticket: explain how the concepts learned in the previous three
lessons will enable them to solve stoichiometric problems. (this will be
the topic in the next lesson)
Objective
 Identify/solve different types of stoichiometric
problems.
 Molar volume of gas at STP = 22.4.
Lesson
 Focus lesson lecture each mass-mass, mass-volume,
and volume-volume stoichiometric problems. Have
students help lead through the sample problems on the
board. Students take notes.
 Students complete worksheet working in groups of four.
The students can decide how to split up the questions.
Each student should have a copy of the answers.
Assessment
 Worksheet to be worked on in class in groups. Each student hands in a
copy of the answers two classes from now. The extra day allows students
to collaborate with their group members outside of class.
www.uwsp.edu/education/pcook/unitplans/docs/Stoichiometry.doc Pg. 28

Assign both pre-lab questions for the Stoichiometry Gizmo. These
questions must be done before entering the computer lab. Students
must bring the Gizmo handout package to the computer lab next class.
http://cs.explorelearning.com/materials/StoichiometrySE.pdf
Misconceptions
 What the “Molar volume of gas at STP = 22.4 “means; molar volume can
be substituted for moles.
 Watch YouTube of molar volume questions. Have class debate on how to use
the molar volume.
Objective
 Identify/solve different types of stoichiometric problems.
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Evaluate chemistry on the Internet.
Lesson
 Students meet in the computer lab.
Have students pair up.
 Do the Stoichiometry Gizmo on the
Internet and fill in the handout.
http://www.explorelearning.com/index.cfm?meth
od=cResource.dspDetail&ResourceID=515
 Go to the http://www.quia.com/jg/4059.html
website. Take turns challenging each
other to games, or take turns playing
(while helping each other to review).
Assessment
 Students hand in Gizmo worksheet at the end of class.
http://cs.explorelearning.com/materials/StoichiometrySE.pdf

Observe students to make sure they are participating and understanding
the concepts of the Quia games.

Exit ticket on blank lined paper: “What happens if there is an excess
amount of one reactant?” Teacher reviews the exit tickets after class and
returns them in next class.
Objective
 Determine the limiting reactant of a chemical reaction.
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Calculate the amount of product formed in a chemical reaction, where reactants are not in
stoichiometric proportions.
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Calculate percent yield, using theoretical and actual yield.
Lesson
 Give students the stoichiometry flowchart handout.

Focus lesson lecture on how to identify the limiting reactant in a reaction. Walk students
through a sample problem. Students take notes.
http://www.youtube.com/watch?v=hwEqoShnBsg

Focus lesson to explain expected yield, actual yield, and how to calculate percent yield.
Walk students through a sample problem. Students take notes.

Show students the following slideshow of real world uses of stoichiometry:
http://www.wiziq.com/tutorial/73848-Chemistry-Stoichiometry-Real-Life-Stoichiometry

Jigsaw activity: questions on worksheet.
Assessment
 Students hand in all completed jigsaw questions by the end of class.
Students who wish to submit their handouts the following class will
receive a maximum mark of a B-.
www.uwsp.edu/education/pcook/unitplans/docs/Stoichiometry.doc Pg. 32
Misconceptions
 When the mass of both reactants is given, students have difficulty
recognizing which is limiting and which is in excess. Students will often
(a) randomly select one of the given masses as limiting or excess. (b) Not
balance the equation. (c) Assume the smaller mass is the limiting
reagent.
 Need to point out that these are not trick questions
 Stress the common steps for using moles in mole ratios for balanced equations.
Objective
 Predict how much product will be made.

Calculate the percent yield.
Lesson
 Students conduct a lab titled Balloon Races.
Assessment
 Students hand in the completed lab report at the
beginning of next class.
http://www.google.ca/url?sa=t&source=web&cd=5&ved=0CDgQFjAE&url=http%3A%2F%2Fdhsacademics.des
oto.k12.mo.us%2FLinkClick.aspx%3Ffileticket%3DA0Ie6Oafmok%253D%26tabid%3D457%26mid%3D14
86&rct=j&q=When%20all%20of%20the%20liquid%20in%20the%20solution%20has%20boiled%20away
%2C%20remove%20the%20flask%20from%20the%20hot%20plate.%20%20The%20powder%20that%2
0you%20observe%20inside%20is%20the%20product%20of%20the%20reaction%2C%20sodium%20ace
tate.%20%20&ei=EygxTqLSCMPqgQebyPGBDQ&usg=AFQjCNFnDJGaZHixYohrA5_7hPfoNh4zWA
Objective
 Test combustion properties in mixtures with
varied mole ratios. Somewhat of a guided inquiry
lab.

Determine what factors determine the
explosiveness of the reaction of hydrogen with
oxygen.
Lesson
 Students conduct a lab titled Micro Mole Rockets.
Assessment
 Students hand in the completed lab report at the
beginning of next class.
www.csd509j.net/cvhs/kirscha/MicroMoleRockets%200708.doc
Objective
 Use basic knowledge of formula weight, stoichiometry, the scientific
method and limiting reagents to solve a mysterious death.
Lesson
 The class computer (with speakers and projector) will be used to run the
program. Students will fill in the provided handouts with the evidence
presented to them.
 Lesson plan link: http://www.chemcollective.org/mr/
 To run through internet: http://collective.chem.cmu.edu/MixedReception/game/main.html
Assessment
 Hand in worksheets for marking at end of class.

STSE project due. (Was assigned in lesson 1).

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Read the chemical safety information (MSDS)
Identify the safety equipment
Dress appropriately for the chemistry lab (no sandals, no contact lenses
during labs, etc.)
Do not pipette by mouth.
Don’t taste or sniff chemicals
Don’t casually dispose of chemicals down the drain...
Don’t eat or drink in the lab.
Don’t play mad scientist, haphazardly mixing chemicals.
Inform teacher of any spills or accidents. Clean up immediately.
Lesson 1
 Discuss stoichiometry in manufacturing, medicine, geologists (test for CaCO3),
space (CO2 scrubbers), air bag inflation, catalytic converters, etc.
 Real world example with Smores activity.
devacaf.caes.uga.edu/main/lessonPlan/SMoreLP.pdf
 Assign an STSE project for the stoichiometry unit. Use the curriculum
documents in SCH3U D1.1 and D1.2 for topic ideas of how stoichiometry is
present in the real world. Students may choose a performance-based
assessment from the following website:
http://www.emtech.net/Alternative_Assessment.html
Lesson 7
 Show students the following slideshow of real world uses of stoichiometry:
http://www.wiziq.com/tutorial/73848-Chemistry-Stoichiometry-Real-Life-Stoichiometry
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Lesson 1: Film canister explosion of sodium bicarbonate and water
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Lesson 1: PEOE react KMnO4 with NaHSO3
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Lesson 3: Titration using the Virtual Chem Lab
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Lesson 10: Mixed Reception murder mystery
Please note:
Resources are incorporated into the slides.
Pictures without website addresses were found using Google.
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