Can you say Stoichiometry?
Section IA – Vocabulary
Below is a list of all of the vocabulary terms used in this subnit. By the end of the
subunit, you will be able to write a working definition of each term and correctly
use each term.
 actual yield
 excess reagent

 limiting reagent
 percent yield
 stoichiometry
 theoretical yield
Section IB – Key Concepts
1) Calculating amounts using Chemical Equations.
2) Limiting Reagents and Percent Yield
Section 2 –– Outside Class Assignments
Thoughtfully do each of the following assignments. Include all your reasoning and
show all your work wherever it seems appropriate. Due dates for each assignment
will be given in class. (Please remember - homework that is passed in late is
automatically discounted 15%.)
1) Make a concept map using the following terms: mole ratio, actual yield,
theoretical yield, chemical equation, limiting reagent, excess reagent, reagent,
and percent yield.
2) Harry is a CIT at Camp Hapless where, as a surprise for his 5 year-old campers,
he is planning to make frozen orange juice popsicles and thumbprint cookies for
tomorrow. Harry has 12 campers in his unit. He figures each will eat at least 2
pops and 4 cookies. Each of his popsicle freezer trays makes 6, 4 ounce
popsicles. The following list of ingredients makes 2 dozen thumbprint cookies: 1
cup margarine, ½ cup brown sugar, 2 egg yolks, 1 tsp vanilla, 2 cups flour and ½
tsp salt.
a) How much orange juice, flour, sugar, eggs, vanilla, butter and salt will he
need to feed his group? (You might choose to create a table listing all the
ingredients. In any event show how you organized your data and calculations
to keep track of all the information you needed.)
b) When he gets home from camp, Harry checks the kitchen for ingredients to
make sure he doesn’t have to go to the store. In the refrigerator he finds a
half-gallon of orange juice, a half dozen eggs, 4 sticks of butter (each stick
contains ½ c of butter) and a half full bottle of vanilla. In the pantry he
finds 3 cups of flour. 1 cup of brown sugar and a half full box of salt.
i) List the excess reagents Harry finds.
ii) List the limiting reagents Harry finds.
iii) What ingredient(s) does Harry need to buy and how much does he need
to buy?
c) Unfortunately when Harry is finished making cookies he comes up 3 cookies
short of what he needs. (He probably shouldn’t have sampled so much of the
cookie dough.)
i) What was Harry’s theoretical yield for the thumbprint cookies?
ii) What was Harry’s actual yield for the thumbprint cookies?
iii) What was Harry’s percent yield for the cookies?
3) Harry has benefited from his camp (and chemistry class) experience and
decides to raise money for the Tanzania trip by selling “MCAS care packages” to
sophomores the week perform MCAS exams. He got permission to set up a table
on Main St. Each care package contains 6 of his now famous thumbprint cookies
(T), two prefrozen Snickers bars (S), a pair of recycleable ice packs (I), a cool
Fruit2O (F2O), and 3 Power bars (Pb). In addition to the food, he is also planning
to include a No. 2 pencil (P), a $5 calculator (C), an order form for more care
packages (Of), and a survey questionnaire (Q).
a) As part of the team, Harry asks you to create a list of all the materials and
food items he will need if you sell 200 packages. (Don’t forget the box and
the ice packs.)
i) Write a balanced equation for preparing an MCAS care package
ii) Calculate the number of each item needed for 200 packages.
b) Harry uses your list to order everything except the cookies. When the
boxes come in, he counts the items. The numbers don’t add up. Do you still
have enough to make 200 packages?
 300 Snickers bars
 400 ice packs
 100 bottles of Fruit2O
 600 power bars
 400 No 2 pencils
 250 calculators
 300 order forms
 250 questionnaires
i) List the excess reagent (excepting the cookies).
ii) List the limiting reagents (excepting the cookies).
iii) What was your theoretical yield for the packages?
iv) What was the actual yield for the packages?
v) What was the percent yield for the packages?
4) Plants manufacture glucose (C6H12O6) and oxygen gas from gaseous carbon
dioxide and water vapor.
a) Write a balanced chemical equation for this reaction including the states of
the compounds (i.e. (s), (l), (g), (aq)).
b) Interpret this chemical equation for photosynthesis in terms of
i) relative numbers of particles,
ii) molecular ratios
iii) numbers of moles, and
iv) masses of reactants and products.
5) Referring back to the above photosynthesis equation,
a) How many moles of glucose are produced from 2 moles of water vapor?
b) How many moles of oxygen are produced from 4 moles of carbon dioxide?
c) If 18 grams of glucose are produced, what mass of carbon dioxide is
required?
d) If 18 grams of oxygen are produced, what mass of water vapor is required?
e) If 18 grams of oxygen are produced, what volume of carbon dioxide is
required?
f) If 18 grams of glucose are produced, what volume of water vapor is
required?
g) 10 grams of water vapor reacts with 50 grams of carbon dioxide?
i) How much glucose will be produced?
ii) How much oxygen will be produced?
iii) Which is the limiting reagent?
iv) Which is the excess reagent?
h) 5 liters of carbon dioxide gas reacts with 10 liters of water vapor, what is
the mass of glucose produced?
i) In practice, the 5 liters of carbon dioxide gas only produces 4 liters of
oxygen gas.
i) What is the theoretical yield of oxygen gas?
ii) What is the actual yield of oxygen gas?
iii) What is the percent yield of oxygen gas?
j) Often the number of molecules on one side of the equation is different from
the number of molecules on the other side of the equation. Why doesn’t this
fact disprove the law of conservation of matter?
k) Explain this statement:” Mass and atoms are conserved in every chemical
equation, but moles will not necessarily be conserved”.
6) For practice with stoichiometry and simple chemical reactions do the following
problems
a) #9 and 10 WSMW p244
b) #11 and 12 WSMW p 245
c) #15, WSMW p249
d) #16 WSMW p249
e) #19 and 22 WSMW p250
f) #37 WSMW p262
7) For practice with stoichiometry and limiting reagents do the following problems
a) #23 and 24 WSMW p254
b) #25 WSMW p255
c) #26 and 38 WSMW p 256
d) #44, 51, 53 and 56 WSMW p262-263
8) For practice with percent yield do the following problems
a) #27 and 28 WSMW p 258
b) #30 and 32 WSMW p259
c) #73 WSMW p264
Section 3 –In Class Activities
1) Lecture / slides
2) Demonstrations
3) Student Labs
a) Copper Chloride Lab again
b) Practice problems
c) Magnesium and HCl
4) Class Projects
a) The stoichiometry of air bags
Section 4 –Textbook and Further Readings
1) Wilbraham, Staley, Matta, Waterman pp236-260