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Mole Review
1.) Calculate the number of moles in 60.4L of O2.
2.) How many moles are there in 63.2g of Cl2?
60.4L O2
22.4L O2
1 mol O2 = 2.7 mol O2
63.2g Cl2
70g Cl2
1mol Cl2 = 0.903mol Cl2
Tiny Tyke Tricycle Company
F + S + 3W + H + 2P → FSW3HP2
Scheduled to make 640 tricycles. How many wheels should they order?
Proportional Relationships
Proportional Relationships
I have 5 eggs. How many cookies can I make?
3/4 c. brown sugar1 tsp vanilla extract2 eggs2 c. chocolate chipsMakes 5 dozen cookies.
2 1/4 c. flour1 tsp. baking soda1 tsp. salt1 c. butter3/4 c. sugar
5 eggs 5 doz.2 eggs = 12.5 dozen cookies
Ratio of eggs to cookies
Proportional Relationships• Stoichiometry– mass relationships between substances in a
chemical reaction• for example: you can determine the amount of a
compound required to make another compound– based on the mole ratio
• Mole Ratio– indicated by coefficients in a balanced equation
2 Mg + O2 2 MgO2 Moles of magnesium react with 1 mole of oxygen to form 2
moles of magnesium oxide.
2 Mg + O2 2 MgO
What would be the mole ratio of magnesium to magnesium oxide?
2 : 2Conversion factor = 2 mol Mg
2 mol MgO What would be the mole ratio of oxygen to
magnesium?1 : 2
Conversion factor = 1 mol O2
(Mole Ratio) 2 mol Mg
Practice
5 F2 + 2NH3 N2F4 + 6HF1. What is the mole ratio of NH3 to F2? Write the mole ratio as a conversion factor.
2. What is the mole ratio of HF to N2F4?Write the mole ratio as a conversion factor.
2:5
2mol NH3
5mol F26:1
6mol HF1mol N2F4
Stoichiometry Steps
1. Identify known & unknown.2. Convert known to mole. (if necessary)3. Use Mole Ratio.4. Convert moles to unknown unit. (if
necessary)
known
Mol of known
Mol of unknown
Mole ratio- get from equation
Mol of unknown
Units of unknown
Mass-Mass Stoichiometry
• Mass of reactants equals the products• Law of Conservation of Mass• ONLY mass and atoms are conserved in every
chemical reaction
Known g 1 mol Known
Molar massKnown
mol unknown
mol known
Mol ratio- get from equation
Molar mass unknown
1 mol unknown
Mass-Mass Stoichiometry
#1
The reaction of fluorine with ammonia produces dinitrogen tetrafluoride and hydrogen fluoride.
5F2 + 2 NH3 → N2F4 + 6HF
How many grams of NH3 are required to produce 7.38g HF?
Mass-Mass Stoichiometry
#2
5F2 + 2 NH3 → N2F4 + 6HF
How many grams of N2F4 can be produced from 265g F2?
Mass-Mass Stoichiometry
#3
2C2H2 + 5O2 → 4CO2 + 2H2O
How many grams of oxygen are required to burn 52.0g C2H2?
• Calculate the number of grams of NH3 produced by the reaction of 5.40 g of hydrogen with an excess of nitrogen.
N2 + 3H2 → 2NH3
C. Stoichiometry ProblemsC. Stoichiometry Problems
__S + __O2 → __SO3 Write the equation. Balance the equation. How many moles of SO3 are produced when
there are 4.5 moles of S? Known = Unknown =
Mole-Mole Examples
#1
2C3H7OH + 9O2 → 6CO2 + 8H2O Write the equation. Calculate the moles of oxygen needed to
react with 3.40 moles of isopropyl alcohol.
Mole-Mole Examples#2
Isopropyl alcohol (C3H7OH) burns in the air to this equation:
2C3H7OH + 9O2 → 6CO2 + 8H2O
Find the moles of water when 6.20 mol O2 reacts with C3H7OH.
Mole-Mole Examples
#3
Volume-Volume Stoichiometry
• Formula to use:
Known (L) 1 mol known mol unknown 22.44 L unknown 1 22.4 L known mol known 1 mol unknown
C3H8 + 5O2 → 3CO2 + 4H2O
If 20 liters of oxygen are consumed in the above reaction, how many liters of carbon dioxide are produced?
Volume Example
#4
Limiting Reactants/Reagents
• Available Ingredients– 4 slices of bread– 1 jar of peanut butter– 1/2 jar of jelly
Limiting Reactant/Reagents bread
Excess Reactants/Reagents peanut butter and jelly
Limiting Reactants/Reagents
• Limiting Reactant/Reagent– used up in a reaction– determines the amount of product
• Excess Reactant/Reagent– added to ensure that the other reactant is
completely used up– cheaper & easier to recycle
Limiting Reagents
1. Write a balanced equation.
2. For each reactant, calculate the amount of product formed.
3. Smaller answer indicates:– limiting reactant– amount of product
Limiting Reagents
79.1 g of zinc react with 0.90 L of HCl. Identify the limiting and excess reactants. How many liters of hydrogen are formed at STP?
Zn + 2HCl ZnCl2 + H2 79.1 g ? L0.90 L
Limiting Reagents
79.1g Zn
1 molZn
65g Zn
= 27.3 L H2
1 molH2
1 molZn
22.4 LH2
1 molH2
Zn + 2HCl ZnCl2 + H2 79.1 g ? L0.90 L
Limiting Reagents
0.90L HCl
1 molHCl
22.4
L HCl
= 0.45 L H2
1 molH2
2 molHCL
22.4 LH2
1 molH2
Zn + 2HCl ZnCl2 + H2 79.1 g ? L0.90 L
Percent Yield
• Percent yield- the ratio of the actual yield to the theoretical yield
• Actual yield- the amount of product formed when a reaction is carried out in the laboratory
• Theoretical yield- the calculated amount of product formed during a reaction
Percent Yield
• When 45.8 g of K2CO3 react with excess HCl, 46.3 g of KCl are formed. Calculate the theoretical and % yields of KCl.
K2CO3 + 2HCl 2KCl + H2O + CO2
45.8 g ? g
actual: 46.3 g
Mole - MoleKnown mol of unknown
mol of known
Mol Ratio – from equationMass - Mass
Known g
molar mass known
1 mol known mol of unknown
mol of known 1 mol unknown
molar mass unknown
Known L
22.4 L known
1 mol known mol of unknown
mol of known 1 mol unknown
22.4 L unknown
particles
6.02 × 1023 particles
6.02 × 1023 particles
OROR
OR
Other
Formulas to Use