Download CHEM121 Lecture Ch5 student

CHEM 121
Chapter 5
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The Mole
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12 eggs =
12 bagels =
6.02 x 1023 hydrogen atoms =
6.02 x 1023 water molecules =
How many water molecules are in 3.5 moles of water?
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Moles of Elements in a Formula
How many moles of each element are in 1 mole of water?
How many moles of each element are in 1 mole of glucose?
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Molar Mass
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Examples:
Carbon
Water
Atomic mass?
Molecular mass?
Molar mass?
Molar mass?
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Calculations with Molar Mass
You measure out 10.0 g of water.
How many moles of water do you have?
If a piece of metal displaces 2.2 mL water,
how many water molecules has it displaced?
(Assume the density of water is 1.0 g/mL.)
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Chemical Equations
Physical Change:
Chemical Change:
Chemical Equation:
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Types of Reactions
Mg
A
+
B
+
O
O
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Types of Reactions
A
H
B
O
H
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Types of Reactions
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A
+
B
C
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A
B
+
C
D
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Chemical Equations
_____________ and ___________ involved in change
1.
2.
3.
4.
5.
Ex. Reaction of magnesium solid and oxygen
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Reaction Equivalents
C3H8 (g) + 5 O2 (g)  3 CO2 (g) + 4 H2O (g)
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1
1
5
2
molecule C3H8 reacts with _______ molecules O2
molecule C3H8 produces _______ molecules CO2
molecule C3H8 produces _______ molcules H2O
molecules O2 produces _______ molecules CO2
molecules C3H8 produces _______ molecules CO2
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Ionic Equations
• Molecular equations
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• Total ionic equations
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• Net ionic equations
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Example: HCl and NaOH
Precipitation Reactions
• Type of replacement reaction
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Example: Aqueous sodium iodide and lead (II) nitrate
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Stoichiometry
the study of mass relationships in chemical equations
Can’t compare mass to mass
Go to moles first
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Reaction Calculations
1.
2.
3.
4.
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Sample Problem
How much carbon dioxide (in grams) is produced
when 3.00 g of ethanol (C2H6O) combusts in air?
How much oxygen gas is used up to combust 5.00 g
of ethanol?
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5-minute review
How many grams of oxygen are needed to react
with 1 mole of CH4 to create water?
Hint: carbon dioxide is also a product.
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Yields
• Theoretical yield:
• Actual yield:
–
• Percent yield:
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Limiting Reactants
What if we have:
8 scoops of ice cream
6 cherries
100 mL of syrup.
How many sundaes can we make?
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Chemical Reactions Involving
a Limiting Reactant
hydrazine (N2H4) and dinitrogen tetraoxide are
liquids that ignite to form nitrogen gas and water
vapor
How many grams of nitrogen gas form when 100. g of
N2H4 and 200. g of dinitrogen tetraoxide are mixed?
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Redox Reactions
• Reduction and oxidation
• Movement of e- from one reactant to another
• 2 Mg (s) + O2 (g) --> 2 MgO (s)
• LEO GER
• Reducing agent? Oxidizing agent?
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Oxidation Numbers (O.N.)
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Any element has O.N. =
1A(1) ions =
2A(2) ions =
H ion can only =
Oxygen ion only =
Halogen ions usually =
The sum of all atoms O.N. in a compound =
Examples: ZnCl2
sulfur trioxide
potassium sulfate
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3-minute review
What is the O.N. of each atom in CaCO3?
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Redox Reaction?
CaO (s) + CO2 (g) → CaCO3 (s)
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3-minute Review
What’s been oxidized in each reaction?
Cu (s) +
AgNO3 (aq) →
N2 (g) + H2 (g)
→
Ag (s) + Cu(NO3)2 (aq)
NH3 (g)
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