Stoichiometry

Report
Stoichiometry
Chemistry Matter and Change Chapter 11
CHAPTER 11 BIG IDEA
Mass relationships in
chemical reactions
confirm the law of
conservation of mass
Chemistry Matter and Change
11.1 Defining Stoichiometry
11.1 MAIN IDEA
The amount of each reactant
present at the start of a
chemical reaction
determines how much
product can form.
11.1 OBJECTIVES
Describe the types of relationships
indicated by a balanced chemical
reaction.
State the mole ratios from a
balanced chemical reaction.
11.1 REVIEW VOCABULARY
Chemical reaction
Reactant
Product
Q: Why was the mole
of oxygen molecules
excited when he
walked out of the
singles bar?
A: He got Avogadro's
number!
11.1 NEW VOCABULARY
Stoichiometry
Mole ratio
Composition stoichiometry
Reaction stoichiometry
Cookies
Ingredients
2 1/4 cups all-purpose flour
1 teaspoon baking soda
1 teaspoon salt
1 cup butter, softened
3/4 cup granulated sugar
3/4 cup packed brown sugar
1 teaspoon vanilla extract
2 large eggs
2 cups (12-oz. pkg.) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels
1 cup chopped nuts
Yield: 5 dozen cookies
If you have only one egg, how many cookies can you make?
What information do you need?
Cookies
Ingredients
2 1/4 cups all-purpose flour
1 teaspoon baking soda
1 teaspoon salt
1 cup butter, softened
3/4 cup granulated sugar
3/4 cup packed brown sugar
1 teaspoon vanilla extract
2 large eggs
2 cups (12-oz. pkg.) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels
1 cup chopped nuts
Yield: 5 dozen cookies
If you have only one egg, how many cookies can you make?
1 egg
60 cookies
2 egg
= 30 cookies
Cookies
Ingredients
2 1/4 cups all-purpose flour
1 teaspoon baking soda
1 teaspoon salt
1 cup butter, softened
3/4 cup granulated sugar
3/4 cup packed brown sugar
1 teaspoon vanilla extract
2 large eggs
2 cups (12-oz. pkg.) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels
1 cup chopped nuts
Yield: 5 dozen cookies
If you need to make 100 cookies, how much flour do you need?
What information do you need?
Cookies
Ingredients
2 1/4 cups all-purpose flour
1 teaspoon baking soda
1 teaspoon salt
1 cup butter, softened
3/4 cup granulated sugar
3/4 cup packed brown sugar
1 teaspoon vanilla extract
2 large eggs
2 cups (12-oz. pkg.) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels
1 cup chopped nuts
Yield: 5 dozen cookies
If you need to make 100 cookies, how much flour do you need?
What information do you need?
100 cookies
2.25 Cups flour
60 cookies
= 3.75 C flour
Cookies
Ingredients
2 1/4 cups all-purpose flour
1 teaspoon baking soda
1 teaspoon salt
1 cup butter, softened
3/4 cup granulated sugar
3/4 cup packed brown sugar
1 teaspoon vanilla extract
2 large eggs
2 cups (12-oz. pkg.) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels
1 cup chopped nuts
Yield: 5 dozen cookies
If you have 3 teaspoons of salt and 5 eggs, how many cookies can you make?
Cookies
Ingredients
2 1/4 cups all-purpose flour
1 teaspoon baking soda
1 teaspoon salt
1 cup butter, softened
3/4 cup granulated sugar
3/4 cup packed brown sugar
1 teaspoon vanilla extract
2 large eggs
2 cups (12-oz. pkg.) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels
1 cup chopped nuts
Yield: 5 dozen cookies
3 t salt
60 cookies
= 180 cookies
1 t salt
5 eggs
60 cookies
2 eggs
= 150 cookies
Reactions are Recipes
Stoichiometry
• Two types
– Composition stoichiometry: deals with mass
relationships of elements in a compound
– Reaction stoichiometry: deals with the mass
relationships between products and reactants
in a chemical reaction
The Key is MOLE RATIOS
• All chemical reactions are described in
moles
• You can convert moles of one substance
to moles of another substance given a
BALANCED EQUATION
Recall
Moles
Practice
• For the equation
– N2+3H22NH3
– What is the mole ratio for nitrogen to hydrogen?
1 mole N2
3 mole H2
=1
– What is the mole ratio for hydrogen to ammonia?
3 mole H2
2 mole NH3
=1
1 mole N2
2 mole NH3
=1
– What is the mole ratio for nitrogen to ammonia?
C6H12O6 + 6 O2  6 H2O + 6 CO2
• reaction
reactiontype:______________________
type:______________________
• If 12
was
consumed,
howhow
12 moles
molesofofoxygen
oxygen
was
consumed,
many
were
manymoles
molesofofCO
C26H
were consumed?
12O6produced?
2H2O2  2H2O + O2
• reaction
reaction type:______________________
type:______________________
• If 3 moles
produced,what
what is
is the
molesofHoxygen
consumed,
2O2 areare
mass
thatthat
wasisproduced?
massofofwater
oxygen
produced?
CAN YOU…
Describe the types of relationships
indicated by a balanced chemical
reaction.
State the mole ratios from a
balanced chemical reaction.
Chemistry Matter and Change
11.2 Stoichiometric Calculations
11.2 MAIN IDEA
The solution to every
stoichiometry problem
requires a balanced
chemical reaction.
11.2 OBJECTIVES
List the sequence of steps used in
solving stoichiometric problems.
Solve stoichiometric problems.
11.2 REVIEW VOCABULARY
Chemical reaction
Diatomic element
Are you part of
the solution or
part of the
precipitate?
The formula that always works:
• You may not always need the whole thing
g “A”
Given
mol “A”
mol “B”
g “B”
g “A”
mol “A”
mol “B”
Balanced
equation
Periodic
table
Periodic
table
2 NaOH + 1 CaBr2  2 NaBr + 1
Ca(OH)2
• reaction type:______________________
• If 27.3 g NaOH is consumed, how many
moles of calcium hydroxide are produced?
• If 84.2 g of calcium bromide are
consumed, how many moles of sodium
hydroxide are consumed?
3 Pb + 2 H3PO4  3 H2 + 1 Pb3(PO4)2
• reaction type:______________________
• If 14.7 g of lead is consumed, what mass
of hydrogen was produced?
• If 87.24 g of Lead phosphate needs to be
produced, what mass of phosphoric acid is
needed?
CAN YOU…
List the sequence of steps used in
solving stoichiometric problems.
Solve stoichiometric problems.
Chemistry Matter and Change
11.3 Limiting Reactants
11.3 MAIN IDEA
A chemical reaction stops
when one of the reactants is
used up.
11.3 OBJECTIVES
Identify the limiting reactant in a
chemical equation.
Identify the excess reactant and
calculate the amount remaining
after the reaction is complete.
Calculate the mass of a product
when the amounts of more than
one reactant are given.
Calculate the maximum yield and
amount of excess reactant
remaining.
11.3 MAIN IDEA
Percent yield is a measure of
the efficiency of a reaction.
11.3 NEW VOCABULARY
Limiting reactant
Excess reactant
11.3 REVIEW VOCABULARY
Molar mass
Q: What do
you call a tooth
in a glass of
water?
A: One molar
solution.
Limiting Reagent
• You have 16 T PB, 8 TB jelly and 4 slices of
bread.
• Which one is the limiting reagent?
• Which are the excess reagents?
Limiting reagent problems
1. Calculate the yield of any of the products
(If you have to solve for one, use that one
and save yourself some steps!)
2. The one that gave you the least amount
of product is the limiting reactant
3. All others are excess reactants
If you have 8 car bodies and 36 tires, what will you have
left over and how many complete cars will you have?
4 tires + 1 body  1 car
• Given 8 bodies and 36 tires
8 bodies
1 car
= 8 cars
1 body
36 tires
1 car
4 tires
= 9 cars
limiting
What is left over?
• Calculate what you used then subtract
8 cars
4 tires
1 car
36 tires
- 32 tires
4 tires
= 32 tires
2.00 g sample of ammonia is mixed with 4.00 g of oxygen. Which is
the limiting reactant and how much excess reactant remains after the
reaction has stopped?
• 4 NH3(g) + 5 O2(g) 4 NO(g) + 6 H2O(g) A
How much is left?
• Figure out how much was used and
subtract from the initial amount
CAN YOU…
Identify the limiting reactant in a
chemical equation.
Identify the excess reactant and
calculate the amount remaining
after the reaction is complete.
Calculate the mass of a product
when the amounts of more than
one reactant are given.
Calculate the maximum yield and
amount of excess reactant
remaining.
Chemistry Matter and Change
11.4 Percent Yield
11.4 OBJECTIVES
Calculate the theoretical yield of a
chemical reaction from data.
Determine the percent yield for a
chemical reaction.
11.4 REVIEW VOCABULARY
Process
Yield
Q: What is the
name of 007's
Eskimo cousin?
A: Polar Bond.
11.4 NEW VOCABULARY
Theoretical yield
Actual yield
Percent yield
Theoretical yield
• Calculated value
• If 120. g of propane, C3H8, is burned in
excess oxygen, how many grams of water
are formed?
Actual yield
• The amount measured (actual)
• If 120. g of propane, C3H8, is burned in
excess oxygen and 140. g of water are
formed, what is the percent yield?
actual
% yield 
 100
theoretica l
Percent Yield
• Theoretical: 196 g water
• Actual: 140. g water
140 g water
% yield 
100
196 g water
 71.4% yield
CAN YOU…
Calculate the theoretical yield of a
chemical reaction from data.
Determine the percent yield for a
chemical reaction.

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