Stoichiometry!
Friday Jan 29 Turn in Emp. lab/ Begin Stoichiometry notes / practice
Monday Feb 1 Computer sim
Tuesday Feb 2 Mass to mass / practice problems
Wednesday Feb 3 Graphic Org.
Thursday Feb 4 Quiz: mass to mass & mole to mole
Friday Feb 5 Lab - Production of silver
Monday Feb 8 Limiting reactant / problems
Tuesday Feb 9 % yield minilab
Wednesday Feb 10 Quiz – on limiting reactant & % yield
Thursday Feb 11 Review/Workday
Friday Feb 12 ***TEST*** / NB check
Essential Question
How do chemists figure out how much product can be produced in a reaction?
Key Questions
What are the molar ratios in a balanced equation?
What are the distinctions between theoretical yield, actual yield & % yield?
Georgia Performance Standard
SC2 d. Identify and solve different types of stoichiometric problems, specifically relating mass to moles and mass to mass.
SC2 e Demonstrate the conceptual principle of limiting reactants.
Vocabulary that you should know:
Stoichiometry, mole ratio, limiting reactant, excess reactant,
% yield, theoretical yield, actual yield
Notebook includes:
vocabulary
Stoichiometry notes/practice
Graphic organizer
Limiting Notes/practice
% yield Notes/practice
Minilab
Computer minilab
+2 choices from the following page
Plus two choices from the following:
If you make 80+ on the quiz,
Choose one:
1) Write a poem or song or rap explaining how to work a mass to mass
stoichiometry problem. (3 verses + chorus)
2) Draw a 4 panel cartoon that demonstrates that you know the difference
between a limiting reactant and excess reactant. (4 color minimum)
3) Make a flyer in Publisher that is a study quide for this unit. Include
your vocab words and mass to mass graphic organizer. (4 color + 2
picture minimum)
AND . . .
Choose one:
Research and write one or two paragraphs describing one of the following: (Include a
related balanced equation for each.)
a) How can a forensic chemist use stoichiometry to determine whether a
confiscated white substance is cocaine.
b) Describe how Alka-Seltzer works and how this relates to stoichiometry.
c) How do rebreathing gas masks work and how do they make use of stoichiometric
ratios.
d) Explain how an air bag in a car uses stoichiometric ratios.
e) Explain how MRE’s (meals ready to eat) heat up and how this relates to
stoichiometry.
If you make below 80 on the quiz, watch 2 of these, take notes on them and & include
them in your notebook.
http://www.gpb.org/chemistry-physics/chemistry/801
&
http://www.gpb.org/chemistry-physics/chemistry/802
http://www.kentchemistry.com/moviesfiles/chemguy/advanced/ChemguyStoich.htm
http://www.khanacademy.org/video/stoichiometry?playlist=Chemistry
http://www.bozemanscience.com/chemistry/
http://lessons.chemistnate.com/basic-chemistry.html
Name: _______________________ Pd: ______
Basic Stoichiometry PhET Lab rvsd 2/2011
Let's make some sandviches!
Introduction:
When we bake/cook something, we use a specific amount of each ingredient. Imagine if you
made a batch of cookies and used way too many eggs, or not enough sugar. YUCK! In
chemistry, reactions proceed with very specific recipes. The study of these recipes is
stoichiometry. When the reactants are present in the correct amounts, the reaction will produce
products. What happens if there are more or less of some of the reactants present?
Procedure: PhET Simulations  Play with the Sims  Chemistry  Reactants, Products, and
Leftovers
If a yellow bar drops down in your browser, click on it and select "Allow Blocked Content"
Part 1: Making Sandviches:
is a simulation of a two-reactant synthesis reaction. In this
case, one reactant will be limiting, while the other will be in excess.
4) Take some time and familiarize yourself with the simulation.
5) Set the reaction to a simple mole ratio of
3) The
2:1:1
6) Complete the table below while making tasty cheese sandwiches:
Bread Used
Cheese Used
Sandwiches Made
5 slices
5 slices
4 slices
3slices
2 sandwiches
6 slices
3 sandwiches
Excess Bread
Excess Cheese
1 slice
0 slices
4 slices
Part 2: Real Chemical Reactions:
7) Now let's work with real chemical reaction, one that creates a very entertaining
BOOM!
8) What is the mole ratio for the reaction of hydrogen and oxygen to produce water?
9) Complete the table below while making water H2O from hydrogen H2 and oxygen O2:
Hydrogen Molecules H2
Oxygen Molecules O2
4 molecules
4 molecules
7 molecules
6 molecules
9 moles
Water Molecules H2O
Excess H2
Excess O2
4 molecules
0 molecules
0 molecules
4 moles
1 moles
0 moles
1.5 moles
0 moles
0 moles
8 moles
4.0 moles
2.5 moles
1.5 moles
10) Notice that the labels changed from molecules to moles. This does not change the
mole ratio, as a mole is simply a large number of molecules. How many molecules is a
mole? _________________
11) Now try producing ammonia, a very important chemical in industry and farming.
12) What is the mole ratio for the production of ammonia?
13) Complete the table below:
Moles N2
Moles H2
3 moles
6 moles
6 moles
3 moles
1.5 moles
Moles NH3
Excess N2
Excess H2
4 moles
2 moles
0 moles
4.0 moles
14) Combustion of hydrocarbons like methane CH4 produce two products, water and carbon
dioxide CO2.
15) What is the mole ratio for the combustion of methane?
16) Complete the table below: WATCH FOR FRACTIONS
mol CH4
mol O2
mol CO2
mol H2O
Excess mol CH4
Excess mol O2
4 mol
4 mol
3 mol
6 mol
2 mol
4 mol
3 mol
17) The BEST PART: Challenge other members of your lab group to the
.
Your First Score:_______lvl__ Your Best Score:________lvl__ Your Lab Group's Best
Score:________lvl__
Stoichiometry problems # 1:
1)
Chlorine is used by textile manufacturers to bleach cloth. Excess chlorine is
destroyed by its reaction with sodium thiosulfate, Na2S2O3 :
Na2S2O3 + 4Cl2 + 5H2O  2NaHSO4 + 8HCl
a. How many moles of Na2S2O3 are needed to react with 0.12mole of Cl2?
b.
How many moles of HCl can form from 0.12mole of Cl2?
c.
How many grams of H2O are required for the reaction of 0.12mole of
Cl2?
d.
How many grams of H2O react if 0.24mol HCl is formed?
2) The incandescent white of a fireworks display is caused by the reaction of
phosphorous with O2 to give P4O10.
4P
a.
+
5O2  P4O10
How many grams of O2 are needed to combine with 6.85g of P?
b.
How many grams of P4O10 can be made from 8.00g of O2?
c.
How many grams of P are needed to make 7.46g P4O10?
3) In dilute nitric acid, HNO3, copper metal dissolves according to the
following equation:
3Cu + 8HNO3  3Cu(NO3)2 + 2NO + 4H2O
a.
How many grams of HNO3 are needed to dissolve 11.45g of Cu?
b.
How many grams of NO are produced when 52.6 g of Cu(NO3)2 is produced?
Stoichiometry Practice: Limiting Reactants (aka limiting reagents)
1. Using the reaction, 4Al + 3O2 2Al2O3, identify the limiting reactant in each of the
following
A) 25.0 moles Al and 35.0 moles O2
B)
75.0gO2 and115gAl
2) Identify the limiting reactant when 10.0g H2O reacts with 4.5g Na to produce NaOH
and H2.
2Na + 2H2O  2Na
+
H2
3)Identify the limiting reactant when 12.5L of H2S at STP is reacted with a solution
containing 24.0g KOH to form K2S and H2O. H2S + 2KOH  K2S + 2H2O
4)
3.5g Zn and 3.5g S are mixed together and heated to produce ZnS.
Zn(s) + S(s) ZnS (s)
a)What is the limiting reactant?
b)What mass of ZnS can be produced?
5)
Barium nitride is produced from the combination reaction between 22.6g solid
barium and 4.2g nitrogen gas?
3Ba +N2Ba3N2
a)What is the limiting reactant?
b)What mass of Barium Nitride can be produced?
6)
Aluminum reacts with Oxygen gas to produce Aluminum Oxide.
4Al(s) + 3O2(g) 2Al2O3(s).
a. If a 200.0.g sample of Al is reacted with 175.0 g of O2 at STP, what is the limiting
reagent?
b. What mass of Aluminum Oxide can be produced?
c. How much excess reactant would be left over?
Stoichiometry:
Percent Yield
2) 9.00 g of Al react with an excess of H3PO4 in this reaction
2Al + 2H3PO4 2AlPO4+ 3H2
3) What mass of AlPO4 could theoretically be produced?
a) What is the percent yield of this reaction if you actually recovered only 30.0 g of AlPO 4?
2) 100.0 g of H3PO4 react with 25.0 g Al to produce AlPO4 and Hydrogen gas? (use the equation from #1)
b) What is the limiting reactant?
c) What is the theoretical yield of AlPO4 for this reaction?
d) What is the % Yield for the reaction if you recovered 105.0 g of AlPO4?
3) Octane (C8H18) burns in oxygen gas to produce carbon dioxide and water. When 320g of octane is burned in an
oxygen rich environment, 392g of water is recovered.
2 C8H18
+
25 O2 
18 H2O
+
16 CO2
4.Determine the theoretical yield of water.
5.Determine the % yield of water.
4) (Challenge problem)
When 2.80g Al(NO3)3 combines with excess NaOH, and 0.996g Al(OH)3 is recovered.
1) Write a balanced equation for this double replacement reaction.
2) Determine the limiting reactant.
3) Fine the theoretical yield of Al(OH)3.
4) Determine the % yield.
b.