Transcript Key Concept 16

Unit 9: Stoichiometry
Define this word?
Bellringer: S’Mores
• How many S’mores could you make with the
ingredient below? Explain your reasoning and
how you calculated your answer (must be at
least three sentence)
Real Life Application
• We cannot forget about the law of
conservation of mass.
• The mass of what we put in must be equal
to what we get out.
• Key Concept 1: The excess reactants are
all the leftover unused reactants. (The
reactant that’s leftover).
Real Life Application
• Since we have conservation of mass we
also need to take into consideration that
limits reactions.
• Key Concept 2: The limiting reactant limits
the extent of the reaction and, thereby,
determines the amount of product formed.
(The reactant that's all used up).
Real Life Application
• What wrong with having excess?
What is Capitalism?
• “a political system in which a country’s trade
and industry are controlled by private owners
for profit”
Why is this Relevant?
• Push you desk in to shoulder partners: Briefly discuss
both of these questions and be prepared to share.
– If companies want to make a profit, what do they want to
avoid?
– If they don’t pay attention to waste, what are the
outcomes?
Compounding Pharmacies
• What are they?
– Prepare specific medications for individualized patients.
– Medication’s ingredients are mixed together in the exact
strength and dosage required by the individual patient.
– Good for patients with allergies.
Not your typical Pharmacy!
How do you think this relates?
• With your shoulder partner, discuss why you
think that compounding pharmacy is an
excellent example of a profession that has to
be mindful of limiting and excess reagents.
– Why is is important that they pay attention excess
and limiting reagents?
Compounding Pharmacist
Mortar and Pestle Compounding Pharmacy
At the END OF UNIT 9 you will be able to
compound 2 grams of calcium carbonate, the active
ingredient in Tums for the Mortar and Pestle
Compounding Pharmacy using stoichiometry and good
lab techniques.
Compounding Pharmacist
CaCl2 (aq) + 2KCO3 (aq)  Ca(CO3)2 (s) + 2KCl (aq)
You want to make 2 grams of Ca(CO3)2 how much
reactants would you have to mix?
Closure- Exit Pass
2Al(s) + 3CuCl2(aq) → 3Cu(s) + 2AlCl3(aq)
1. Define excess vs. limiting reagent.
2. If you were an chemical engineer
manufacturing aluminum chloride, what
would you want to be your excess reagent (Al
is less expensive than CuCl2) and why?
Particle and Mole Relationships
• Chemical reactions stop when one of the
reactants is used up.
• Key Concept 3: Stoichiometry is the study
of quantitative relationships between the
amounts of reactants used and amounts of
products formed by a chemical reaction. (It’s
the math that figures out how to not have
excess)
• So based on how much reactant you put
in you can calculate how much product
you will get out.
Particle and Mole Relationships (cont.)
Key
Concept: 4
Particle and Mole Relationships (cont.)
•
Key Concept 5: A mole ratio is a ratio between the
numbers of moles of any two substances in a balanced
equation.
• This can only be determined from a balanced chemical
equation.
• Let practice: What is the mole-to-mole ratio for……
a. 10C2H4O + 15O2  20CO2 + 2H2O
b. CH4 + 2O2  CO2 + 2H2O
c. H2 + O2  H2O
Hide Conversion Factors
The quantities of a conversion factor
have to be equal.
= Sign
The word per
The word for
The word in
Ratio
New Conversion Factor
Mole to Mole Ratio
What are the other two conversion factors you already know
that are related to moles?
Avogadro's Principle
Key Concept 6: Avogadro’s principle
states that equal volumes of gases at the
same temperature and pressure contain
equal numbers of particles.
Particle and Mole Relationships (cont.)
Key
Concept: 4
Stoichiometry and Volume-Volume Problems
Coefficients in a balanced equation represent
volume ratios for gases.
Avogadro's Principle (cont.)
Key Concept 7: The molar volume of a gas
is the volume 1 mol occupies at 0.00°C and
1.00 atm of pressure.
REVIEW: What is STP?
Key Concept 8: At STP, 1 mol of gas occupies
22.4 L.
NEW CONVERSION FACTOR (LAST ONE)
Let’s make a Tool Box
Converting Units (cont)
Factor Labeling Step
1. Determine what the question is asking you to solve
for.
2. Determine what is given in the problem to be
converted.
3. Identify and plug in the appropriate conversion
factors as fractions (what is on top must also be on
bottom).
4. Cancel units
5. Verify your answer. (Units must match units in step 1.
If the answer doesn’t match, repeat 3 and 5).
Practice Makes Perfect
Key Concept 9: How many moles are in 15 liters
of Oxygen gas at STP?
Practice Makes Perfect
Key Concept 10: If I have 2.5 moles of Ca(OH)2
how many grams do I have?
Practice Makes Perfect
Key Concept 11: If I have 2 liters of water vapor
(H20) how many grams do I have?
Using Stoichiometry
Key Concept 12: All stoichiometric calculations
begins with a balanced chemical equation.
4Fe(s) + 3O2(g)  2Fe2O3(s)
Using Stoichiometry
4Fe(s) + 3O2(g)  2Fe2O3(s)
Key Concept 13:
Grams--- Mole---Mole--- Grams
How many grams of iron are required to react with 15.0 g oxygen
gas in the following reaction?
How many grams of iron (III) oxide are produced is 15.0 g oxygen
gas reaction in excess iron?
Using Stoichiometry
4Fe(s) + 3O2(g)  2Fe2O3(s)
Key Concept 14:
How many grams of iron (III) oxide are produced is 25
grams of oxygen react with 30 grams of iron, what is
the limiting factor?
Stoichiometry of Reactions Involving Gases
The gas laws can be applied to calculate the stoichiometry
of reactions in which gases are reactants or products.
2H2(g) + O2(g) → 2H2O(g)
Key Concept 15: How many liters of water vapor
are produced when 3.5 liter of oxygen and
excess hydrogen gas react?
Using Stoichiometry (cont.)
Key Concept 16:
How many grams of lithium nitrate will be needed to
make 250 grams of lithium sulfate, assuming that you
have an adequate amount of lead (IV) sulfate to do the
reaction?
__Pb(SO4)2 + __LiNO3  __Pb(NO3)4 + __Li2SO4
Using Stoichiometry (cont.)
Calculating the Product when a Reactant
is Limiting
Key Concept 16:
2Cu(s) + S(s) → Cu2S(s)
80.0g Cu reacts with 25.0g S
A. Determine which is the limiting reactant.
B. Calculate how much Cu2S if formed?
Socrative
What volume will 18 moles of C4H4 gas take
up at STP?
A. 22.4 liters
B. 403 liters
C. 0.8 liters
D. None of the above
Socrative
How many mol of hydrogen gas are
required to react with 1.50 mol oxygen gas
in the following reaction?
2H2(g) + O2(g) → 2H2O(g)
A. 0.75
B. 3
C. 36
D. None of the above
Socrative
How many liters of hydrogen gas are
required to react with 3.25 liters of oxygen
gas in the following reaction?
2H2(g) + O2(g) → 2H2O(g)
A. 2.00
B. 3.25
A. A
C. 4.00
B.
B
D. 6.50
C. C
D. D
Compounding Pharmacist
Mortar and Pestle Compounding Pharmacy
Situation: I told Mrs. Driebe and Mrs. Lieb that you
could:
• Predict the products in a double replacement
reaction
• Balance the equation
• Practicing stoichiometry.
Goal: Is to compound 2 grams of calcium carbonate,
the active ingredient in Tums for the Mortar and Pestle
Compounding Pharmacy using stoichiometry and good
lab techniques.
Compounding Pharmacist
CaCl2 (aq) + 2KCO3 (aq)  Ca(CO3)2 (s) + 2KCl (aq)
You want to make 2 grams of Ca(CO3)2 how much
reactants would you have to mix?
How does Ca(CO3)2 work in the stomach?
How do antacids relieve heartburn?
Closure: Exit Pass
• On average a Pharmacists makes $50 an hour
in Arizona. Today you did one job a Pharmacist
is trained to do. Could you see yourself as a
Pharmacist? Why or why not.