Chocolate Chip Cookies
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2.25 cups flour
8 Tbsp butter
0.5 cups shortening
0.75 cups sugar
0.75 cups brown sugar
1 tsp salt
1 tsp baking soda
1 tsp vanilla
0.5 cups Egg Beaters
1 bag chocolate chips
Chocolate Chip Cookies
• 2.25 cups flour
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How much?
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8
0.5
0.75
0.75
1
1
1
0.5
1
Tbsp butter
cups shortening
cups sugar
cups brown sugar
tsp
salt
tsp
baking soda
tsp
vanilla
cups Egg Beaters
bag
chocolate chips
What units?
Of what?
Chocolate Chip Cookies
•
•
•
•
How much?
•
•
•
•
•
•
2.25
8
0.5
0.75
0.75
1
1
1
0.5
1
flour
butter
shortening
sugar
brown sugar
salt
baking soda
vanilla
Egg Beaters
chocolate chips
Of what?
Chocolate Chip Cookies
•
•
•
•
How much?
•
•
•
•
•
•
2.25
8
0.5
0.75
0.75
1
1
1
0.5
1
cups flour
Tbsp butter
cups shortening
cups sugar
cups brown sugar
tsp
salt
tsp
baking soda
tsp
vanilla
cups Egg Beaters
bag chocolate chips
What units?
Of what?
Get on with it!
What does this have to do with
CHEMISTRY?
2.25 cups flour + 8 Tbsp butter + 0.5 cups shortening +
0.75 cups sugar + 0.75 cups brown sugar + 1 tsp salt +
1 tsp baking soda + 1 tsp vanilla + 0.5 cups Egg Beaters + chips
unit
substance
coefficient
(177ºC)
1 batch of chocolate chip cookies!
(a synthesis reaction)
Welcome to
STOICHIOMETRY
What is stoichiometry?
• Composition stoichiometry deals with the
mass relationships of elements in compounds.
• Reaction stoichiometry involves the mass
relationships between reactants and products
in a chemical reaction.
• All reaction stoichiometry calculations start
with a balanced chemical equation.
Let’s Revisit the Cookies…
For 1 batch:
•
•
•
•
•
•
•
•
•
2.25 cups flour
8 Tbsp butter
0.5 cups shortening
0.75 cups sugar
0.75 cups brown sugar
1 tsp salt
1 tsp baking soda
1 tsp vanilla
0.5 cups Egg Beaters
The Egg Beaters I have are close to expiring!
I’d like to use the rest of them in this recipe. I
have 1.5 cups of Egg Beaters.
How many batches of cookies can I
make with that many Egg Beaters?
Let’s Revisit the Cookies…
For 1 batch:
•
•
•
•
•
•
•
•
•
2.25 cups flour
8 Tbsp butter
0.5 cups shortening
0.75 cups sugar
0.75 cups brown sugar
1 tsp salt
1 tsp baking soda
1 tsp vanilla
0.5 cups Egg Beaters
I have 1.5 cups of Egg Beaters.
How many batches of cookies can I
make with that many Egg Beaters?
1.5 cups E.B.
1 batch cookies
x
=
0.5 cups E.B.
3.0 batches of cookies
Let’s Revisit the Cookies…
For 1 batch:
•
•
•
•
•
•
•
•
•
2.25 cups flour
8 Tbsp butter
0.5 cups shortening
0.75 cups sugar
0.75 cups brown sugar
1 tsp salt
1 tsp baking soda
1 tsp vanilla
0.5 cups Egg Beaters
I have 1.5 cups of Egg Beaters.
How much butter do I need to deplete
(use up) the Egg Beaters?
1.5 cups E.B.
8 Tbsp butter
x
=
0.5 cups E.B.
24 Tablespoons of butter
… Back to Chemistry
• There are three types of stoichiometry
problems:
– Mole-Mole problems (1 conversion)
– Mass-Mole problems (2 conversions)
– Mass-Mass problems (3 conversions)
given
required
Stoichiometry Problems
• Stoichiometric problems are solved by using
ratios from balanced chemical equations to
convert the given quantity.
• A mole ratio is a conversion factor that relates
the amount in moles of any two substances
involved in a chemical reaction.
• This information is obtained from the
balanced chemical equation.
Mole Ratios
• Example:
2 H2 O
2 H2 + O2
• The relationships between product and reactants
or reactants can be expressed in the following
mole ratios:
Mole Ratios
2 H2 + O2
2 H2O
2 mol H 2
2 mol H 2O
or
2 mol H 2O
2 mol H 2
1 mol O2
2 mol H 2O
or
2 mol H 2O
1 mol O2
2 mol H 2 1 mol O 2
or
1 mol O 2
2 mol H 2
Practice
• For each reaction, write all possible mole
ratios.
2Al2O3 (l)  4Al(s)  3O2 (g)
2 mol Al2O3
4 mol Al
or
4 mol Al
2 mol Al2O3
2 mol Al2O3
3 mol O2
or
3 mol O 2
2 mol Al2O3
4 mol Al 3 mol O2
or
3 mol O2
4 mol Al
2HgO (s)  2Hg (l)  O 2 (g)
2 mol HgO
2 mol Hg
or
2 mol Hg
2 mol HgO
2 mol HgO
1 mol O 2
or
1 mol O 2
2 mol HgO
1 mol O 2
2 mol Hg
or
2 mol Hg 1 mol O 2
Mole-Mole Problems
Example:
2 H2 O
2 H2 + O2
How many moles of water can be formed from 0.5 mol H2?
0.5 mol H2
x
2 mol H2O
2 mol H2
=
0.5 mol H2O
Mole-Mole Practice
3CuSO4 +
2 Al
Al2(SO4)3 + 3 Cu
1. Convert 0.5 mol CuSO4 to mol Cu
0.5 mol CuSO4 x
3 mol Cu
=
0.5 mol Cu
=
0.8 mol CuSO4
3 mol CuSO4
2. Convert 0.5 mol Al to mol CuSO4
0.5 mol Al
x
3 mol CuSO4
2 mol Al
Mass – Mole Problems
• Step 1: Write a BALANCED EQUATION.
• Step 2: Calculate the molar mass of your
given substance and convert from mass to
moles.
• Step 3: Determine the mole ratio from the
coefficients in the balanced equation.
• Step 4: Set up the conversion and solve.
Mass-Mole Problems
Example:
2 H2 O
2 H2 + O2
How many moles of water can be formed from 48.0 g O2?
48.0 g O2
x
1 mol O2
32.00 g O2
x
2 mol H2O
1 mol O2
=
3.00 mol H2O
Mass-Mole Practice
3 CuSO4
+
2 Al
+
Al2(SO4)3
3 Cu
Mole ratio
1. a.
13.5 g Al
x
1 mol Al
3 mol CuSO4
x
26.98 g Al
b.
13.5 g Al
x
1 mol Al
2 mol Al
x
26.98 g Al
c.
13.5 g Al
x
1 mol Al
26.98 g Al
0.751 mol
CuSO4
=
1 mol Al2(SO4)3
=
2 mol Al
x
3 mol Cu
2 mol Al
=
0.250 mol
Al2(SO4)3
0.751 mol
Cu
Mole – Mass Practice
3 Ca + 2 AlCl3
0.095 mol AlCl3 x 3 mol Ca
2 mol AlCl3
3 CaCl2 + 2 Al
x 40.08 g Ca
1 mol Ca
=
5.7 g Ca
Mass-Mass Problems
Example:
2 H2 O
2 H2 + O2
How many grams of water can be formed from 48.0 g O2?
48.0 g O2
x
1 mol O2
32.00 g O2
x
2 mol H2O
1 mol O2
x
18.02 g H2O
1 mol H2O
= 54.1 g H2O
Mass-Mass Practice
3 CuSO4
+
2 Al
Al2(SO4)3
+
3 Cu
Mole ratio
1. a. 8.5 g Al
x
1 mol Al
x
26.98 g Al
3 mol CuSO4
x
2 mol Al
159.61 g CuSO4
=
1 mol CuSO4
75 g CuSO4
b. 8.5 g Al
x
1 mol Al
26.98 g Al
x
1 mol Al2(SO4)3
2 mol Al
x
342.14 g Al2(SO4)3
1 mol Al2(SO4)3
54 g Al2(SO4)3
=
Mass-Mass Practice
c. 8.5 g Al
x
1 mol Al
26.98 g Al
x
3 mol Cu
2 mol Al
x
63.55 g Cu
1 mol Cu
30. g Cu
=