Stoichiometry Notes
Describe the types of
relationships indicated
by a balanced chemical
equation.
State the mole ratios from
a balanced chemical
equation.
Particle and Mole Relationships
• 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)
• Chemical reactions stop when one of the
reactants is used up.
• So based on how much reactant you put
in you can calculate how much product
you will get out.
Particle and Mole Relationships (cont.)
•
•
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……
1. 2C12H22O3 + 32O2  24CO2 + 22H2O
2. CH4 + 2O2  CO2 + 2H2O
3. H2 + O2  H2O
Using Stoichiometry
All stoichiometry calculations begin with a
balanced chemical equation.
4Fe(s) + 3O2(g)  2Fe2O3(s)
GramsMoleMole RatioGrams
Using Stoichiometry (cont.)
Using Stoichiometry (cont.)
How many moles of SO3 are formed if you start
with 5 moles of Sulfur and have excess Oxygen?
__S + __O2  __SO3
Using Stoichiometry (cont.)
How many moles of Sulfur do you need to create
45 grams of SO3 if you have excess Oxygen?
__S + __O2  __SO3
Using Stoichiometry (cont.)
How many grams of Sulfur do you need to create
45 grams of SO3 if you have excess Oxygen?
__S + __O2  __SO3
Using Stoichiometry (cont.)
How many grams of Na2SO4 will be formed if you
start with 200 grams of NaOH and you have an
excess of H2SO4?
__NaOH + __H2SO4  __H2O + __Na2SO4
Answer the following in your NOTES
How many moles of Na2SO4 will be formed if you
start with 35 grams of H2SO4 and you have an
excess of NaOH?
__NaOH + __H2SO4  __H2O + __Na2SO4
How many grams of LiNO3 will be needed to make
250 grams of Li2SO4, assuming that you have
enough Pb(SO4)2 to do the reaction?
__Pb(SO4)2 + __LiNO3  __Pb(NO3)4 + __Li2SO4
Real Life Application
Ingredients
•2 1/4 cups all-purpose flour
•1 teaspoon baking soda
•1 teaspoon salt
•1 cup (2 sticks) butter, softened
•3/4 cup granulated sugar
•3/4 cup packed brown sugar
•1 teaspoon vanilla extract
•2 large eggs
•2 cups (12-oz. pkg.) NESTLÉ® TOLL HOUSE® Semi-Sweet
Chocolate Morsels
•1 cup chopped nuts
Real Life Application
• What goes into a cell phone:
•
– Glass
– Plastic
– Aluminum
– Magnets
– Bromine
– PVC
– Heavy metals like lead, tin, cadmium and chromium
Heavy metals, PVC and bromine are all chemicals that
we do not want getting into our water and need to be
disposed of carefully. We do not want extra amounts
of these.
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.
• 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 what
limits reactions.
• 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
• Knowing what limiting reagents and
excess are we can think about the most
cost effective method for producing things.
• We do not want a lot of excess so we
need to determine what chemical(s) or
ingredient(s) to make the limiting reagent
• The most expensive chemical is always
the limiting reactant.
Excess vs. Limiting
2Al(s) + 3CuCl2(aq) → 3Cu(s) + 2AlCl3(aq)
If you were an chemical engineer manufacturing
aluminum chloride, what would you want to be
your excess reagent and why?
Compounding Pharmacist
• Compounding pharmacy is called when Physician
need to prescribe a very specific medication,
prepared by a pharmacist, for a patient's
individual needs.
• A compounding pharmacy is used when:
• allergic to a dye or filler in a commercial
tablet.
• capsule is too large, or the dose is too high,
which is common in pediatric cases.
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
• Practice 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
MgCl2 (aq) + 2KCO3 (aq)  Mg(CO3)2 (s) + 2KCl (aq)
You want to make 2 grams of Mg(CO3)2 how much reactants would you
have to mix?
Bell Ringer
• On average a Pharmacists makes $50 an hour
in Arizona. This week you did one job a
Pharmacist is trained to do. Could you see
yourself as a Pharmacist? Why or why not.