My Favorite “No”
Today you will need goggles and a lab apron.
Write the balanced chemical equation: When
heated NaHCO3 reacts to form sodium
carbonate, carbon dioxide, and water.
Investigation: All That Remains
Predict the outcome and then test your prediction:
How much solid mass will remain after decomposing
2.00g of sodium hydrogen carbonate by heating? (Hint:
2NaHCO3(s) -> Na2CO3(s) + CO2(g) + H2O(g))
Spend 5 minutes working on your prediction, design,
and safety considerations with your group.
Investigation: All That Remains
Class Discussion
After class discussion, write any changes to your
original procedure and begin your experiment.
Once you have completed the experiment, answer the
questions at the bottom of page 2.
Homework
Complete page 2 and the pre-lab on page 4.
My Favorite “No”
Today you will need goggles and a lab apron.
How many moles of carbon dioxide are in a
226 L sample of CO2?
Mole Review
• For conversions between mass,
volume (of a gas), and number of
mole map
particles, we use the _________to
dimensional analysis
guide our _________________.
Dimensional Analysis Review
With dimensional analysis, multiply the given by
one or more conversion factors in the form of a
12 donuts = 1 dozen donuts
fraction.
Example:
=
36 donuts
1
=
36 donuts
Chemical Conversion Factors
1 mole = molar mass (g)
1 mole = 6.02 x 1023 particles
(atoms, ions, molecules, f.un.)
1 mole = 22.4L of a gas at STP
Practice Problems
1. What is the mass of 4 moles of oxygen gas?
2. What is the volume of 3.4 x 1025 molecules of CH4 at STP?
Cu-Fe Lab
• In this lab exercise, iron nails will react with a
solution of copper (II) chloride to produce iron (II)
chloride and copper. When the reaction is complete,
the mass of iron used as a reactant and the mass of
copper metal produced will be determined.
• Then using the process of stoichiometry, the
theoretical yield of copper can be calculated,
followed by a percent yield calculation to determine
the efficiency of this chemical reaction.
Cu-Fe Lab
Purpose:
To use stoichiometry to predict the
amount of copper produced.
To calculate the percent yield of copper
using the actual yield found by
experimentation.
Safety:
1)
Wear safety goggles and lab aprons at all times.
2)
All acid spills should be neutralized with baking
soda (NaHCO3).
Cu-Fe Lab
Day 1 Supplies per group:
100 mL beaker (and tape to label)
4.25g copper II chloride
2 iron nails
Sandpaper
25 mL graduated cylinder
Stirring rod
Homework
Complete page 5
1/28 Warm-Up: Balancing
Chemical Equations (Page 6)

Directions: Using coefficients, balance the
following equation -
2 C H + ____O
15
12
6
____
→
____CO
+
____H
6 6
2
2
2O
Cooking Analogy – Click Here

Grill Master K.T. Tigers has the art of grilled cheese sandwich
making down to a science. The Grill Master's recipe requires 2
pieces of cheese between 2 slices of bread, grilled to
perfection. What is the coefficient ratio of the ingredients to the
product?
2
2
1
Cooking

Grill Master Tigers knows that a 20 pack of sliced bread and a
20 pack of sliced cheese will always make the same number of
grilled cheese sandwiches with no leftovers. How many?
•

What happens to the Grill Master's grilled cheese sandwiches if
he changes the quantities of ingredients? Will he have enough
ingredients? Will there be leftovers?
•
•

2 slices of bread and 2 slices of cheese per sandwich will make 10 sandwiches
without any leftover ingredients
Changing the quantity of any single ingredient will change the number of
sandwiches the Grill Master can produce
If all ingredients are not changed in the same proportion, one or more
ingredients will be leftover, or in excess
Practice grilled cheese sandwich making here:
http://phet.colorado.edu/en/simulation/reactants-products-and-leftovers
What Cooking Really Is…
Stoichiometry:

The calculation of quantities in chemical reactions.
Example:
N2 (g) + 3H2 (g) → 2NH3 (g)



The coefficient ratio of substances in this balanced chemical
equation is 1 : 3 : 2
It states, 1 molecule of nitrogen gas reacts with 3 molecules
of hydrogen gas to yield 2 molecules of ammonia gas
OR – 1 mol of nitrogen gas reacts with 3 mol of hydrogen
gas to yield 2 mol of ammonia gas; etc.
Instead of cups, teaspoons, or
tablespoons, we have…

1. Representative Particles:
•
•

1 molecule of nitrogen gas reacts with 3 molecules of
hydrogen gas to produce 2 molecules of ammonia
gas.
It's always in the same coefficient ratio; just like 2
slices of bread plus 2 slices of cheese produce 1
grilled cheese sandwich!
2. Moles:
•
1 mol of nitrogen gas reacts with 3 mols of hydrogen
gas to produce 2 mols of ammonia gas.
And…

3. Mass:
•
•
•

Law of conservation of mass says mass of reactants
must equal mass of products.
Mass of nitrogen gas = 28g and mass of hydrogen
gas = 6g
The sum equals the mass of the products = 34.0g
4. Volume:
•
•
1 mol of gas = 22.4 L @ STP
22.4 L of nitrogen gas reacts with 67.2 L of hydrogen
gas to produce 44.8 L of ammonia.
Mol to Mol Conversion
Calculations


N2(g) + 3H2 (g)
2NH3 (g)
What is the mole ratio of the above
equation?
•1:3:2

Because we know the ratio, we can
calculate to find the number of moles of
another substance.
Example

How many mols of NH3 are produced
when 0.60 mol of nitrogen gas reacts
with hydrogen gas? (show work)
• 1.2 mol NH3
Practice Problems
MnO2 + 4HCl → MnCl4 + 2H2O
1. How many mol of H2O are produced when 3.20 mol
of MnO2 reacts with hydrochloric acid? (show work)
Practice Problems
MnO2 + 4HCl → MnCl4 + 2H2O
2. How many mol of HCl are consumed (used) when
1.65 mol of Manganese (IV) chloride are produced?
(show work)
Practice Problems
MnO2 + 4HCl → MnCl4 + 2H2O
3. How many mol of water are produced when 4.35
moles of MnCl4 are also produced? (show work)
End of Day One of
Stoichiometry
Homework: Page 8
Don’t worry, there will be
more to come… 
My Favorite “No”
How many moles of H2 are in a 5.40g
sample of H2?
You will need a calculator and periodic
table today!
Remember this?
Well, now that you
know how to convert
from moles of one
substance to moles
of another, we can
expand it!
The Mole Highway
RECALL: The Mole Highway...it's been expanded and construction is complete!
Like before, the Mole Highway can be used as a map toward setting up an appropriate
conversion.
The Mole Highway
HOW IT’S USED:
1. Find the starting point; use the value, substance, and unit you are given
2. Find the ending point; use the value, substance, and unit are you being required to solve
3. You must stay on the highway!!!
4. Each road taken represents 1 step in your conversion!
5. Once the destination is reached, solve mathematically by multiplying across the top,
multiplying across the bottom, and dividing the top value by the bottom value.
The Mole Highway
NOTES FOR USE:
1. Before any math can be done, a BALANCED CHEMICAL EQUATION is required.
2. If the starting value isn't in the unit "mol," your first step is to convert it there.
3. Going from mol of substance A to mol of substance B requires a Mol to Mol conversion;
USE YOUR COEFFICIENTS FROM THE BALANCED CHEMICAL EQUATION!
Mass – Mass Calculations
N2(g) + 3H2 (g) → 2NH3 (g)


Like yesterday, in order to go from the mass of one
substance, to the mass of a new substance, a mol to
mol conversion will be necessary.
Steps, from a plan of action:
•
•
•
•
•
Mass A → Mol A → Mol B → Mass B
Convert from mass of substance A to mol of substance A
Convert from mol of substance A to mol of substance B
Convert from mol of substance B to mass of substance B
USE THE MOLE HIGHWAY!
Example
N2(g) + 3H2 (g) → 2NH3 (g)

Calculate the number of grams of NH3 produced by the
reaction of 5.40 g of H2 with excess N2 (g). (show work)
• 31.0 g NH3 (g)
Practice Problems
1. How many grams of O2 (g) are produced when a
sample of 29.2 g of water decomposes?
• Write a balanced formula.
• 2H2O →
2H2 + O2
• Get a plan of action:
• g water → mol water → mol O2 → g O2
• (show work)
Practice, con’t.
2. Using the same equation, how many liters of hydrogen
gas are produced when 1.33 x 1017 molecules of water
decompose? (show work)
Practice, con’t.
2SO2 (g) + O2 (g) → 2SO3 (g)
3. How many liters of O2 are needed to produce 19.8 L
of SO3? (show work)
Practice, con’t.
4. How many molecules of oxygen are consumed in the
formation of 187.4 L of SO3? (show work)
Practice, con’t.
5. How many molecules of Sulfur dioxide are
consumed in the formation of 4.41 x 1027 molecules
of sulfur trioxide? (show work)
End of Day Two
Homework: Page 11
Do not be sad Petry, lots of things
cannot fly: rocks, trees, sticks, Spike!
Don’t worry folks, if you aren’t there
yet, you’ll learn how to fly in
stoichiometry. 
Section 9.3-Limiting Reagent
First back to cooking…
 What is Grill Master Tiger‘s recipe for grilled cheese sandwiches?
•

What happens if the Grill Master receives only half of his order of
cheese for the day?
•

The number of slices of cheese; it is his limiting ingredient, while the bread is his
excess ingredient.
What if the Grill Master received 3 times the amount of cheese he
needed?
•

He can only make half as many sandwiches, or he’ll have to modify his recipe.
So, in this case, what is limiting the number of grilled cheese
sandwiches he can make?
•

2 slices of bread with 2 slices of cheese, grilled to perfection
He’d have left over cheese, it would be the excess ingredient.
What would be limiting him in this case?
•
The bread; there wouldn’t be enough bread to use all of the excess cheese.
Limiting Reagent/Reactant



The same thing applies to chemical
reactions…
N2(g) + 3H2 (g)
2NH3 (g)
1 mol of N2(g) reacts with 3 mol of H2 (g) mol to
form 2 mols of NH3 (g).
•
•
•
What happens if you only have 0.5 mol of nitrogen
gas?
How much hydrogen gas would you use?
How much ammonia would you make?
Limiting Reagent

Limiting Reagent:
• Limits or determines the amount of product
that can be formed in a reaction.

Excess Reagent:
• The reactant that is not completely used up in
a reaction.
Example Problem

Sodium chloride can be prepared by the
reaction of sodium metal with chlorine
gas. Suppose that 6.70 mol of Na reacts
with 3.20 mol of Cl2. What is the limiting
reagent?
Step 1: Write a balanced
equation

2Na (s) + Cl2 (g)
2NaCl (s)
Step 2: Solve for moles of
product for each reactant

To do this, convert the given info for each
reactant (mol, in this problem) to mol of product.

If the original substances are given in grams,
you’d have an extra step – converting mass to
moles – but the rest of the process would be the
same.
Step 3: Determine the max. mol
of product that can be made



You will have two answers for moles of
product Why? There will be one for each
reactant calculation.
So which one do I use? The smaller one
The SMALLER of the two answers is the
maximum product because you only have
enough reactants to make that amount.
You will run out of one of the reactants
before the larger amount is made.
Step 4: Identify the limiting and
excess reactants



Once you know your maximum product, look
all the way to the left of that calculation. The
reactant that produced that smaller amount
of product is your limiting reactant.
It “limited” you to making the smaller of the
two amounts!
The other reactant – that started the other
calculation – is the excess reactant.
Step 5: Solve your problem!

Convert mol of your limiting reagent to mol
of product (or whatever the original question
asks for).
Sample Problem



2Cu(s) + S(s)
Cu2S(s)
1. What is the limiting reagent when
80.0g Cu reacts with 25.0 g of S?
2. What is the maximum number of
grams of copper (I) sulfide produced?
• Cu is the limiting reagent and S is in excess.
• 100.23 g Cu2S
End of Day Three
I’ll Be Back…
Percent Yield
Cooking, yet again… 
 Grill Master Tiger‘s recipe yields 10 grilled cheese
sandwiches when 20 slices of bread and 20 slices of
cheese are used


So, the recipe tells you the theoretical yield:
•
10 sandwiches if followed specifically
What you actually make is the actual yield:
•
•
What if the pack of cheese only had 19 slices? Actual
yield, 9 sandwiches.
What if you cut the ingredients in half? You’d actually
yield 20 sandwiches.

Percent yield:
• The ratio of the actual yield to the theoretical
yield expressed as a percent.
Percent yield = actual yield
X 100%
theoretical yield
• Should the percent yield normally be larger
than 100%?
Example

Using the following equation, what is the
theoretical yield of CaO if 24.8g CaCO3
is heated? What is the percent yield if
13.1g of CaO is produced?

Again, follow the steps…
Step 1:


Convert g of given substance to g of
questioned substance.
Which means…
• 24.8 g of CaCO3
• 13.89 g CaO.
= _____g of CaO.
Step 2:


Find percent yield.
94.31%
My Favorite “No”
Today you will need a calculator, goggles, and a
lab apron.
Write the balanced equation for the synthesis of
carbon monoxide.
Using the equation you wrote, how many moles
of CO can be formed if there is an unlimited
supply of C and 2.4 moles of O2?
My Favorite “No”
1. Write and balance the decomposition
reaction of sodium oxide.
2. If 6.02*1024 molecules of sodium oxide are
used, how many liters of O2 gas will be
formed?