Stoichiometry

1
Stoichiometry

• Chapter 9

2
Totally Up Front
3
Theoretical Yield

• What does the word yield mean? Theoretical?
• This is how much stuff you should get on the
  products side.
• What factors would make it so you dont get all
  that you should?
• Human error, changing containers, etc

4
Some Math

• If you have 12 g of C, how many moles do you
  have?
• If you have 24 g of C, how many moles do you
  have?
• If you have 36 g of C, how many moles do you
  have?
• If you have 48 g of CO2, how many moles do you
  have?

5
Moles

• Convert 10 g of H2O to moles.
• How many grams of H2O do you have if you have 6
  moles?
• If you have 100 g of C6H12O6, how many moles do
  you have?
• If you have 3.456 moles of C6H12O6, how many
  grams do you have?

6
CH4 2O2 ? CO2 2H2O

• If you have 16.04 g of methane, in excess oxygen,
  what mass of oxygen is used in the equation?
• How many moles of methane do you have?
• What is the ratio of moles of methane to moles of
  oxygen?
• How many moles of oxygen are used?
• How many grams is that?

7
Theoretical Yield

• If 10.0 g of C is combined with excess oxygen to
  get carbon dioxide, what mass of CO2 in grams is
  isolated?
• Write the equation.
• How many moles of C do you have?
• How many moles of CO2 does that make?
• How many grams is that?

8
Fe2O3 3CO ? 2Fe 3CO2

• What is the maximum mass of iron, in grams, that
  can be obtained from 454 g of Iron (III) Oxide?
• What mass of CO is needed to reduce iron(III)
  oxide to iron metal?
• This is stoichiometry at its best!!! (Having fun
  yet?)

9
4Al 3O2 ? 2Al2O3

• If you have 6 moles of Al, how many grams of
  Al2O3 is produced?
• If you have 300 g of oxygen, how much Al are you
  using?

10
Do practice worksheet!
11
Moles Aforethought
12
CaO 2NH4Cl ? 2NH3 H2O CaCl2

• If exactly 100.0 g of ammonia is isolated , but
  the theoretical yield is 136 g, what is the
  percent yield?
• If I use 86 g of ammonium chloride are used and
  13 g of water are made, what is my percent yield?

13
Zn Cl2 ? ZnCl2

• What is the percent yield if 65.2 g of ZnCl2 is
  isolated from 35.5 g of Zn?
• 87.9

14
2NaBH4 I2 ? B2H6 2NaI H2

• Suppose 1.203 g of NaBH4 and excess iodine is
  used and you isolate 0.295 g of B2H6. What is the
  percent yield?
• 67.2

15
HCl NaOH ?H2O NaCl

• Suppose you have 40 g of HCl and 60 g of NaOH.
  How much NaCl will you make?
• Must find the limiting reagent!!
• Before you can solve for NaCl, find out if HCl or
  NaOH limits the reaction. Which one is in excess?

16
CO H2 ? CH3OH

• If you have 152.5 kg of CO and 24.5 kg of H2, how
  many grams of CH3OH can be produced?
• 174.5 kg

17
Fe2O3 CO ? Fe CO2

• If you have 18.0 g of iron (III) oxide and 110 g
  of carbon monoxide, how many grams of iron could
  you make?
• 125.9 g

18
Some Vocabulary

• Composition Stoichiometry relationships that
  describe what an element is made up of. (Ex
  calculating molar mass)
• Reaction Stoichiometry using the relationships
  between compounds (Ex Using the mole ratio)

19
Jumpin Jack Flash, Its Glass, Glass, Glass!
20
Stoichiometry in Use

• Combustion of Octane in car engines
• C8H18 25O2 ?16CO218H2O 10900kJ
• What are the two reactants here?
• How are they controlled?

21
Carburetor

• Your engine has three modes of combustion, normal
  speeds, starting, and idling.
• See page 298
• Normal speeds octane is the limiting reagent
• Starting and idling, oxygen is the limiting
  reagent
• Flooding!

22
Pollution

• What else comes out of your gas tank?
• Hydrocarbons, CO, oxides of nitrogen
• Where do these come from?
• Incomplete combustion can allow octane fumes out
  the back.
• Lack of Oxygen can form CO2
• Nitrogen in the air forms oxides of Nitrogen

23
Acid Rain

• Oxides of Nitrogen can form with water in the air
  to form acids.
• Cars use a catalytic converter to convert NO2 ?
  NO O
• That O is not stable and can help form O3, which
  near the earth can cause smog as well