Mole Review 1.) Calculate the number of moles in 60.4L of O 2 . 2.) How many moles are there in 63.2g of Cl 2 ? 60.4L O 2 22.4L O 2 1 mol O 2 = 2.7 mol O 2 63.2g Cl 2 70g Cl 2 1mol Cl 2 = 0.903mol Cl 2
Feb 24, 2016
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
Ch. 9
Math In ChemistryStoichiometry
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 MgOWhat would be the mole ratio of magnesium to
magnesium oxide?2 : 2
Conversion 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 Steps1. Write a balanced equation2. Identify known & unknown.3. Convert known to mole (if necessary), line up
conversion factors.4. Use Mole Ratio.5. Convert moles to unknown unit (if necessary).6. Calculate and write units.
known
Mol of known
Mol of unknown
Mole ratio- get from equation
Mol of unknown
Units of unknown
Mole - Mole Stoichiometry
Formula: known mol mol unknown
mol known
1. Write the known and unknown.2. Use the balanced equation to find the mole
ratio.3. Calculate.
__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
Mass-Mass Stoichiometry• Mass of reactants equals the mass of products, Law of Conservation of Mass• ONLY mass and atoms are conserved in every chemical reaction1. Write the known and unknown.2. Find the molar mass of the known and unknown substances.3. Use mole and molar mass conversion factors from Ch. 7 and mole ratios
from the balanced equation to solve.
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
#1The reaction of fluorine with ammonia
produces dinitrogen tetrafluoride and hydrogen fluoride.
5F2 + 2 NH3 → N2F4 + 6HFHow many grams of NH3 are required to
produce 7.38g HF?
Mass-Mass Stoichiometry
#25F2 + 2 NH3 → N2F4 + 6HF
How many grams of N2F4 can be produced from 265g F2?
Mass-Mass Stoichiometry
#32C2H2 + 5O2 → 4CO2 + 2H2O
How many grams of oxygen are required to burn 52.0g C2H2?
Volume-Volume Stoichiometry
• Formula to use:
Known (L) 1 mol known mol unknown 22.4 L unknown 1 22.4 L known mol known 1 mol unknown
1. Write the known and unknown.2. Use mole and volume conversion factors from Ch. 7 and the
mole ratios from the balanced equation to solve.
C3H8 + 5O2 → 3CO2 + 4H2O
If 25 liters of oxygen are consumed in the above reaction, how many liters of carbon dioxide are produced?
Volume-Volume Example#4
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
Stoichiometry Problems• How many moles of KClO3 must decompose
in order to produce 9 moles of oxygen gas?
9 mol O2 2 mol KClO3
3 mol O2
= 6 mol KClO3
2KClO3 2KCl + 3O2
Known: 9 moles O2
Unknown: moles KClO3
Stoichiometry Problems• How many grams of KClO3 are required to produce
9.00 L of O2 at STP?
9.00 LO2
1 molO2
22.4 L O2
= 32.68 g KClO3
2 molKClO3
3 molO2
122 g KClO3
1 molKClO3
2KClO3 2KCl + 3O2
Known: 9.00 L O2
Unknown: g KClO3
Stoichiometry Problems
• How many grams of silver will be formed from 12.0 g copper?
12.0g Cu
1 molCu
64 g Cu
= 40.5 g Ag
Cu + 2AgNO3 2Ag + Cu(NO3)2
Known: 12.0 g Cu Unknown: g Ag 2 mol
Ag
1 molCu
108 g Ag
1 molAg
Stoichiometry Problems
• How many grams of silver will be formed from 12.0 g copper?
12.0g Cu
1 molCu
64 g Cu
= 40.5 g Ag
Cu + 2AgNO3 2Ag + Cu(NO3)2
Known: 12.0 g Cu Unknown: g Ag
2 molAg
1 molCu
108 g Ag
1 molAg
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
To Determine Limiting Reagents
1. Write a balanced equation.
2. For each reactant, calculate the amount of product formed.
3. Smaller answer indicates:– limiting reactant– actual amount of product
Limiting Reagents79.1 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
= 27.26 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
Limiting Reagents
Zn: 27.26 L H2 HCl: 0.45 L H2
Limiting reagent: HCl
Excess reagent: Zn
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 (mathematical calculation used to make answer keys)
Percent Yield
100yield ltheoretica
yield actualyield %
calculated on paper
measured in lab
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
B. Percent Yield
45.8 gK2CO3
1 molK2CO3
138 gK2CO3
= 49.12g KCl
2 molKCl
1 molK2CO3
74g KCl
1 molKCl
K2CO3 + 2HCl 2KCl + H2O + CO2 45.8 g ? g
actual: 46.3 gTheoretical Yield:
B. Percent Yield
Theoretical Yield = 49.12 g KCl
% Yield =46.3 g
49.12 g 100 = 94.3%
K2CO3 + 2HCl 2KCl + H2O + CO2 45.8 g 49.12 g
actual: 46.3 g