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Chapters 11

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Dimensional Analysis - a problem solving method that focuses on ... 20 brownies. Ammonia Recipe. 1 molecule N2. 3 molecule H2. Yields: 2 molecules NH3. 8/18/09 ... – PowerPoint PPT presentation

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Title: Chapters 11


1
Chapters 11 12
  • The Mole Stoichiometry

2
Dimensional Analysis
  • Dimensional Analysis - a problem solving method
    that focuses on the units that are used to
    describe amount of matter.
  • 1) How many minutes in 3 days?

3
Dimensional Analysis
  • 2) How many centimeters in 8.0 inches?
  • 3) How many inches in 5.25 meters?

4
Dimensional Analysis
  • 4) How many goats can you buy if you have 3
    horses?
  • 2 horses 3 cows
  • 2 goats 1 cow

5
Mole Concept
  • 1 dozen
  • 1 mole

12
particles in 12 grams of carbon-12
6.02 x 1023
6
Mole Concept
  • 1 mole of desks ___________ desks
  • 1 mole of nails ___________ nails
  • 1 mole of pens ___________ pens
  • 1 mole people ________ people ________ hands
  • 1 mole of carbon ______________ atoms
  • 1 mole of water ____________ molecules
  • 1 mole of carbon dioxide __________ molec.
  • ____________ atoms

6.02 x 1023
6.02 x 1023
6.02 x 1023
6.02 x 1023
2 (6.02 x 1023)
6.02 x 1023
6.02 x 1023
6.02 x 1023
3 (6.02 x 1023)
7
Mole Wheel Problemsmoles ?? rep. particles
  • How many atoms in 3.00 moles of carbon?
  • How many moles in 3.57 x 1024 molecules of sugar?

8
Mole Wheel Problems moles ?? volume
  • How much space (volume) would 5.5 moles of carbon
    dioxide occupy at STP?
  • A sample of gas occupies 17.0 liters at STP. How
    many moles is this?

9
Mole Wheel Problems moles ?? mass
  • Whats the mass of 0.125 moles of iron?
  • Whats the mass of 1.1 moles of carbon dioxide?

10
Mole Wheel Problems multi-step problems
  • A sample of oxygen gas has a mass of 85 grams.
    How many moles is this?
  • Whats the mass of 15.0 L of carbon monoxide gas.

11
Mole Wheel ProblemsApplication Problems not
quite mole wheel
  • How many moles of oxygen atoms in one mole of
    CO2? ____
  • How many moles of oxygen atoms in three moles of
    sugar, C12H22O11? ____

12
Mole Wheel Problems Application Problems not
quite mole wheel
  • How many moles of hydrogen in 1.5 moles of C2H6?
  • How many atoms of hydrogen in 1.5 moles of C2H6?
  • How many atoms in 1.5 moles of C2H6?

13
Mole Wheel Problems
  • How many moles of Na ions in 1 mole of Na3PO4?
    ____
  • A sample of sodium phosphate has a mass of 25.0
    grams. How many moles of Na ions?

14
Composition
  • composition the percent mass of each element
    in a compound.
  • H2O
  • Ba(NO3)2

15
Empirical vs. Molecular Formula
  • Molecular Formula
  • Empirical Formula
  • Exs

16
Empirical/Molecular Formulas
  • Given
  • 1) Convert to mass (Assume 100g.)
  • 2) Convert mass to moles
  • 3) Convert moles to simplest ratio (make
    whole s if necessary).

composition
mass composition
mole composition
17
Empirical/Molecular Formulas
  • 1). A compound is found to be 41.9 sodium,
    19.1 phosphorus, and 38.9 oxygen. Determine
    the empirical formula.

18
Empirical/Molecular Formulas
  • 2). A compound is found to be 82.8 carbon and
    17.2 hydrogen. Determine the empirical formula.

19
Empirical/Molecular Formulas
  • Determining the molecular formula from
    experimental data
  • 3) If the molar mass of the compound in 2 is
    58.0 g/mol, what must be the molecular formula?

20
Hydrate Formulas
  • Determination of a hydrate formula
  • 8.00 grams of hydrated barium hydroxide (Ba(OH)2
    x H2O) are heated. 4.35 grams remain after
    heating. What is the formula of this hydrate?

21
Easy Mole Ratios
  • AgNO3 (aq) NaCl(aq) ? AgCl(aq) NaNO3 (aq)
  • If 1 mole of AgNO3 reacts, ____ moles of NaCl are
    needed, ____ moles of AgCl and ___ moles of NaNO3
    are formed.
  • Thus if 2 moles of AgNO3 react, ____ moles of
    NaCl are needed, ____ moles of AgCl and ___ moles
    of NaNO3 are formed.

22
Easy Mole Ratios
  • 2 H2 (g) O2 (g) ? 2 H2O (g)
  • If 2 mole of H2 react, ____ moles of O2 are
    needed, ____ moles of H2O are formed.
  • If 4 mole of H2 react, ____ moles of O2 are
    needed, ____ moles of H2O are formed.

23
Easy Mole Ratios
  • N2 (g) 3 H2 (g) ? 2 NH3 (g)

24
Limiting Reactants
25
Limiting Reactants
  • The KEY to understanding limiting reactants is to
    understand the meaning of a balanced chemical
    equation.
  • Balanced chemical equation
  • Represents the simplest ratio of reactants and
    products for a particular reaction.
  • i.e. THE RECIPE

26
Limiting Reactants
Ammonia Recipe 1 molecule N2 3 molecule
H2 Yields 2 molecules NH3
  • Brownie Recipe
  • 1 egg
  • ½ C. veggie oil
  • 1 C. water
  • Brownie mix
  • Yields
  • 9 x 13 pan
  • 20 brownies

27
Limiting Reactants
Ammonia Recipe 1 mole N2 3 mole H2 Yields 2
moles NH3
Ammonia Recipe 1 molecule N2 3 molecule
H2 Yields 2 molecules NH3
OR
Which can be expressed as
N2 (g) 3 H2 (g) ? 2 NH3 (g)
28
Limiting Reactants
N2 (g) 3 H2 (g) ? 2 NH3 (g)
KEY This balanced equation tells you what RATIO
in which the elements react. NOT how much you
have/make of each.
29
Limiting Reactants
Limiting reactant -
The substance that runs out first in a reaction
Excess reactant -
The substance that remains when the reaction is
complete i.e. its present in excess
30
NaOH (aq) HCl (aq) ? H2O(l) NaCl (aq)
  • If you have 3 mol NaOH and 4 mol HCl
  • Whats your limiting reactant?
  • b. How many moles of product will be formed?

1
31
NaOH (aq) HCl (aq) ? H2O(l) NaCl (aq)
  • If you have 3 mol NaOH and 4 mol HCl
  • Whats your limiting reactant?
  • b. How many moles of product will be formed?

2
32
AgNO3 (aq) BaCl2 (g) ? 2 AgCl (s) Ba(NO3)2
(aq)
  • If you have 5 mol AgNO3 and 3 mol of BaCl2
  • Whats your limiting reactant?
  • b. How many moles of product will form?

1
33
AgNO3 (aq) BaCl2 (g) ? 2 AgCl (s) Ba(NO3)2
(aq)
  • If you have 5 mol AgNO3 and 3 mol of BaCl2
  • Whats your limiting reactant?
  • How many moles of product will form?
  • How many moles of excess reactant remain?

2
34
AgNO3 (aq) BaCl2 (g) ? 2 AgCl (s) Ba(NO3)2
(aq)
  • If you have 5 mol AgNO3 and 3 mol of BaCl2
  • Whats your limiting reactant?
  • How many moles of product will form?
  • How many moles of excess reactant remain?

3
35
N2 (g) 3 H2 (g) ? 2 NH3 (g)
  • If you have 2.5 mol of nitrogen and 6 mol of
    hydrogen.
  • Whats your limiting reactant?
  • How many grams of ammonia form?
  • How many grams of excess reactant remain?

1
36
N2 (g) 3 H2 (g) ? 2 NH3 (g)
  • If you have 2.5 mol of nitrogen and 6 mol of
    hydrogen.
  • Whats your limiting reactant?
  • How many grams of ammonia form?
  • How many grams of excess reactant remain?

2
37
N2 (g) 3 H2 (g) ? 2 NH3 (g)
  • If you have 2.5 mol of nitrogen and 6 mol of
    hydrogen.
  • Whats your limiting reactant?
  • How many grams of ammonia form?
  • How many grams of excess reactant remain?

3
38
Percent Yield/ Percent Error
  • Percent Yield
  • Percent Error

39
Given the following balanced equationCH4 2
O2 ? CO2 2 H2O
  • If 20.0 grams of methane is burned in 40.0 L of
    oxygen gas (_at_STP), how many grams of carbon
    dioxide will be formed?
  • b. If 35.0 grams of carbon dioxide are produced,
    whats the percent yield and percent error?

40
  • 50.0 g. of propane (C3H8) and 200. g. of oxygen
    react. Given the following balanced equation
  • C3H8 5 O2 ? 3 CO2 4 H2O
  • How many grams of water will be formed?

41
  • 35.0 L of nitrogen and 6.72 g. of hydrogen react.
    Given the following balanced equation
  • N2 3 H2 ? 2 NH3
  • What mass of ammonia will be formed?

42
Limiting Reactants
Limiting reactant -
The substance that runs out first in a reaction
it thus LIMITS the amount of products that can be
formed
Excess reactant -
The substance that remains when the reaction is
complete i.e. its present in excess
43
Limiting Reactants
NaOH (aq) HCl (aq) ? H2O (l) NaCl (aq)
  • If you have 3 moles NaOH and 4 moles of HCl
  • Whats your limiting reactant?

44
Limiting Reactants
NaOH (aq) HCl (aq) ? H2O (l) NaCl (aq)
If you have 3 moles NaOH and 4 moles of HCl b.
How many moles of product will be formed?
45
Limiting Reactants
AgNO3 (aq) BaCl2 (g) ? 2 AgCl (s) Ba(NO3)2
(aq)
  • If you have 5 moles silver nitrate and 3 moles of
    barium chloride
  • Whats your limiting reactant?

46
Limiting Reactants
AgNO3 (aq) BaCl2 (g) ? 2 AgCl (s) Ba(NO3)2
(aq)
If you have 5 moles silver nitrate and 3 moles of
barium chloride b. How many moles of product
will form?
47
Limiting Reactants
AgNO3 (aq) BaCl2 (g) ? 2 AgCl (s) Ba(NO3)2
(aq)
If you have 5 moles silver nitrate and 3 moles of
barium chloride b. How many moles of excess
reactant remain?
48
Limiting Reactants
N2 (g) 3 H2 (g) ? 2 NH3 (g)
  • If you have 2.5 moles of nitrogen and 6 moles of
    hydrogen.
  • Whats your limiting reactant?

49
Limiting Reactants
N2 (g) 3 H2 (g) ? 2 NH3 (g)
  • If you have 2.5 moles of nitrogen and 6 moles of
    hydrogen.
  • How many grams of ammonia form?

50
Limiting Reactants
N2 (g) 3 H2 (g) ? 2 NH3 (g)
  • If you have 2.5 moles of nitrogen and 6 moles of
    hydrogen.
  • How many grams of excess reactant remain?

51
Percent Yield/ Percent Error
  • Percent Yield compares the amt. of product you
    made to the amount of product you should have
    made.
  • error actual yield x 100
  • theoretical yield
  • Percent Error tells by what percent you were
    off compared to what you should have made.
  • error diff. between theoretical and actual
    yield x 100
  • theoretical yield

52
Limiting Reactant Problems
  • Given the following balanced equation CH4 2
    O2 ? CO2 2 H2O
  • If 20.0 grams of methane is burned in 40.0 L of
    oxygen gas (_at_STP), how many grams of carbon
    dioxide will be formed?
  • b. If 35.0 grams of carbon dioxide are produced,
    whats the percent yield and percent error?

53
Limiting Reactant Problems
  • 50.0 g. of propane (C3H8) and 200. g. of oxygen
    react. Given the following balanced equation
  • C3H8 5 O2 ? 3 CO2 4 H2O
  • How many grams of water will be formed?

54
Limiting Reactant Problems
  • 35.0 L of nitrogen and 6.72 g. of hydrogen react.
    Given the following balanced equation
  • N2 3 H2 ? 2 NH3
  • What mass of ammonia will be formed?
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