Turn in the following…
Balancing Equations WSWord Equation WS- 1 page WS
Predicting Products Packet- tear off the
last page…put your name on it!
You have 55 minutes to do the test…
2
Chapter 8- Stoichiometry
Big, Scary name….
Just calculations chemists do!
3
Copper Series- Lab 1
Write and balance the equation for the reaction of copper
(Cu) plus nitric acid (HNO3) to produce Copper (II)
nitrate (Cu(NO3)2) plus water (H2O) and nitrogen dioxide
(NO2).
Cu
+ 4HNO3
→
Cu(NO3)2 + 2H2O + 2NO2
4
Lab Concerns
Use the same scales for each lab… they mass slightly
different.
Be sure to record any lab mistakes… too much
reactant, lost product, other booboos.
You will be calculating percent error and trying to
explain the errors.
You may never say that you made a mistake in your
calculations-- there are 3 of you working, there
should be no mistakes!
5
You will be working in groups of 3- be sure to exchange
contact info and be sure to communicate if you will be absent.
Jobs Rotate- Write you job at the top of each lab.
1. Leader- Keeps all on task and makes sure
directions are followed.
2. Scientist- Follows directions and is in charge of
making sure no mistakes occur.
3. Mathematician- insures calculations are correct.
I will pick one lab per group to grade-- you get
whatever score they get…make sure everyone in
your group is completing the lab!
6
Procedure- Using the sharpie.. Put your period
and lab station on the beaker. Ex: 2-1
1.
2.
3.
4.
Determine the mass of your empty beaker.
Determine the mass of the copper.
Send your scientist to the stock room to put
20mL of HNO3 into the beaker
Put on the watch glass and place on the hot
plate in the fume hood.
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Warm Up
Check to be sure that you have the first 4
blanks of your Series 1 Lab complete.
8
Quantitative Analysis
Composition stoichiometry- mass relationships of
elements in compounds.
Reaction Stoichiometry- involves mass
relationships between the reactants and
products in reactions
9
What do the coefficients mean?
Mole Ratios
Coefficients indicate the amount of each material
(Moles or molecules) present in a reaction.
C6H12O6 + 6O2
6CO2 + 6H2O
So… when looking at a balanced equation we can derive a
whole set of conversion factors!
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Ooh! Lets write a bunch!!
C6H12O6 + 6O2
6CO2 + 6H2O
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Mole Ratio- The Definition…
A conversion factor that relates the amounts in
moles of any two substances involved in a
chemical reaction.
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Mole Ratios allow us to do all sorts of cool
calculations. Yipee!
Ex: How many moles of CO2 are produced when 0.38
mol C6H12O6 are burned according to the following
reaction?
C6H12O6 + 6O2
6CO2 + 6H2O
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Mole to Mole Calculations….
Fe2O3 + 3CO
2Fe + 3CO2
1. How many mol CO are necessary to react with 2.2
mol Fe2O3?
2. How many mol Fe are produced if 1.8 mol CO is
used?
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Fe2O3 + 3CO
2Fe + 3CO2
1. How many mol CO are necessary to react with 2.2
mol Fe2O3?
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Mole Ratios
Fe2O3 + 3CO
2Fe + 3CO2
b) How many mol Fe are produced if 1.8 mol CO is
used?
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Stoichiometric Conversions
Congratulations! Now that you’ve mastered the only
new conversion necessary for stoichiometry, We
can convert our mole into other things using
Stoichiometry!
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The following chart summarizes the
conversions we can do:
Number of particles of A
Mass of A
Moles of A
Volume of gaseous A
Number of particles of B
Moles of B
Mass of B
Volume of gaseous B
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So, can we use stoichiometry to determine
the amount of product made in types of
reactions lab?
We used 0.2 g of CuCO3 in the decomposition
reaction.
How much CuO was produced?
CuCO3
CuO + CO2
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Can we determine the amount of magnesium
oxide produced in the synthesis reaction?
We used about 0.5 g of Mg.
Mg + O2
MgO
a. Balance the equation.
b. Place the mass of Mg used in the upper left.
c.
Use DA to determine the theoretical mass of
MgO.
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Important Vocabulary Terms
Theoretical yield- the maximum amount of
product that can be produced from a given
amount of reactant.
Actual Yield- measured amount of a product
obtained from a reaction (in lab).
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What is the theoretical yield (in grams) of both
products in the following reaction if 2.5 g of HCl is
used?
Zn + HCl
a.
b.
c.
d.
ZnCl2 + H2
Balance the equation
Put 2.5g HCl in the upper left
Solve for g of zinc chloride.
Solve for g of hydrogen.
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Warm Up
On your copper lab, #5 asks you to determine
the theoretical yield for Cu(NO3)2. Do the
calculation using your mass determined in #1.
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Let’s make sure you are doing the
other calculations correctly.
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How did you do on the Mass – Mass
WS?
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There are a bunch of other calculations
we can do using the flow chart…
Number of particles of A
Mass of A
Moles of A
Volume of gaseous A
Number of particles of B
Moles of B
Mass of B
Volume of gaseous B
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Stoichiometric Conversions
How many grams of oxygen are produced when
17.5g of H2O2 decompose according to the
following equation?
H2O2
H 2O +
O2
(Don’t forget to balance the equation!)
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Stoichiometric Conversions
How many liters of oxygen are produced when
17.5g of H2O2 decompose according to the
following equation?
H2O2
H 2O +
O2
(Don’t forget to balance the equation!)
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How many molecules of H2O2 are needed to
make 3.5 x 1023 molecules of water?
2H2O2
2H2O + O2
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How many molecules of H2O2 are needed to
make 5.00 g of water?
2H2O2
2H2O + O2
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Try these!
CaCO3 + Mg
→
MgCO3
+
Ca
a) How many molecules of Ca are produced if 39.4g of
MgCO3 are also produced?
b) How many grams of Mg are necessary to react with
0.97 mol CaCO3?
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Copper Lab- Series 2
1.
2.
3.
4.
5.
6.
Obtain the mass of your Cu(NO3)2
Add about 20 ml of distilled water.
Add 30 ml of NaOH
Obtain the mass of your filter paper!!!
Filter the mixture- rinse it well with distilled
water.
Wash out your original beaker (check to be
sure it is still marked with your period and
lab station.)
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Percent Yield

In a perfect world, every student would get a perfect
score on every test.
Alas, we do not live in a perfect world
How do we determine the score you got on the test?
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Percent Yield (cont’d)
In a perfect world, every reaction would produce the
amount of material it is supposed to.
Alas, we do not live in a perfect world.
Percent yield = the ratio comparing the amount of
material actually generated in a reaction to the
maximum amount possible.
l
Percent Yield = Actual Yield x 100
Theoretical Yield
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Percent Yield (cont’d)

The theoretical yield is calculated using
stoichiometry.

The actual yield is found by experimentation.

Key Point: You can never predict the actual
yield or the percent yield.
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Percent Yield
2Mg + O2 → 2MgO
3.2 g of Magnesium reacted with excess
oxygen. 4.9g of MgO was produced in the lab.
Calculate the percent yield.
1.
2.
3.
Balance Equation
Calculate Theoretical Yield
Calculate % Yield
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Warm UpSb2S3(s) + 3Fe(s)
2Sb(s) + 3FeS(s)
When 22.3g of Sb2S3 reacts with excess of Fe, 12.7g
Sb is produced in the lab. What is the percent yield?
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Questions on the Homework?
39
Copper Lab- Series 3
The third reaction has copper (II) oxide and
water being produced from copper (II)
hydroxide. Write and balance the equation.
What type of reaction is it?
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Copper- Series 3
1.
2.
3.
4.
5.
6.
7.
8.
9.
Determine the mass of the Cu(OH)2. Don’t forget to subtract the
mass of the beaker and filter paper!
Open up the filter paper containing your product and transfer as
much of the copper hydroxide as you can into the large beaker.
Put the filter paper in too.
Add 100 ml of distilled water.
Put the large beaker on the hot plate and heat to a gentle boil.
Use forceps to remove the filter paper
Use the squirt bottle to rinse the filter paper.
Decant as much water as possible.
Transfer back into your beaker.
Allow product to settle and decant more water.
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Work on your calculations!
42
Warm Up
The theoretical yield of CuO, calculated using
stoichiometry was 45.3 g. The actual yield was
46.2 g. Determine the percent yield.
Is the yield high or low?
What could explain the yield?
43
Limiting / Excess
Reagents
Let’s think about a peanut butter sandwich…
The recipe calls for 2 pieces of bread and 2 Tsp.
of peanut butter.
Write the reaction:
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Now, we only have so much of each
reactant…
Huge tube o Skippy
12 pieces of bread
How many sandwiches can we make?
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Limiting Reagent (cont’d)

Chemical reactions are much the same way. The balanced
chemical equation is the recipe, telling you how much of each
thing you need.

Often, chemicals are not mixed in the correct amounts,
implying that one chemical will run out before the others.

The chemical that runs out first is called the limiting reagent.

The chemical that has some left over… is in excess. (The
excess reagent)
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Limiting Reagent (cont’d)
a.
b.
c.
d.
Calculate the amount of reactant necessary to use up the given
quantities (2 calculations).
Compare what you have to what you need to determine limiting.
Use the original amount to determine the maximum amount of
products.
Subtract what you use from what you have to determine amount of
excess.
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Limiting and Excess Calculations…
Ex: 5.00g of HCl is mixed with 4.00g of
NaOH according to the following reaction:
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
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Limiting/Excess
You react 54.8g of silver nitrate with 22.2g of
calcium chloride according to the following rxn.
AgNO3 + CaCl2 →
1.
2.
3.
4.
AgCl
+
Ca(NO3)2
Balance the equation.
Determine the limiting.
Calculate the maximum amount of AgCl
Calculate the excess.
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