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eUnit 14: Redox and Electrochemistry
Lesson 14.1: Redox
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Let’s Remind Ourselves of a Few Things
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Remind me of Redox
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Oxidation and Reduction (Redox)
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Oxidation and Reduction (Redox)
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Oxidation and Reduction (Redox)
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Oxidation and Reduction (Redox)
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Oxidation and Reduction (Redox)
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LEO says GER :
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LEO says GER :
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Oxidation and Reduction (Redox)
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Not All Reactions are Redox Reactions
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Assigning Oxidation Numbers
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Rules for Assigning Oxidation Numbers
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Rules for Assigning Oxidation Numbers
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Rules for Assigning Oxidation Numbers
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Rules for Assigning Oxidation Numbers
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Assign Oxidation States
O2
Li3N
ZnSO4
Fe(NO3)2
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Who is oxidized and who is reduced
If the charge becomes more positive (increases) during the reaction, the atom is
losing electrons (being oxidized).
If the charge becomes more negative (reduced) during the reaction, the atom is
gaining electrons (being reduced).
See if you can find the redox:
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Fe(NO3)2
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Who is oxidized and who is reduced
If the charge becomes more positive (increases) during the reaction, the atom is
losing electrons (being oxidized).
If the charge becomes more negative (reduced) during the reaction, the atom is
gaining electrons (being reduced).
See if you can find the redox:
Cu + 2AgNO3  Cu(NO3)2 + 2Ag
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Trends in Oxidation and Reduction
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Spectator Ions
Spectator ions do not participate in the redox reaction. Their oxidation numbers do
not change.
Identify the spectator(s):
Cu + 2AgNO3  Cu(NO3)2 + 2Ag
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Once more from the top
What
What
What
What
What
F2 + CaCl2  CaF2 + Cl2
species is oxidized?
species is reduced?
is the oxidizing agent?
is the reducing agent?
is/are the spectator ion(s)?
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Half Reactions
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Half Reactions
Steps for writing half reactions:
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2.
3.
4.
Assign oxidation states to all species.
Identify reduction and oxidation.
Write the half-reactions.
Balance each for mass and charge.
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Example:
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Write the half-reactions
Cu + 2AgNO3  Cu(NO3)2 + 2Ag
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Write the half-reactions
F2 + CaCl2  CaF2 + Cl2
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Write the half-reactions
N2 + 3H2  2H3N
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Write the half-reactions
Zn + 2HCl  ZnCl2 + H2
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Balancing Redox Rxns
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F2 + CaCl2  CaF2 + Cl2
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Write the half-reactions
N2 + 3H2  2H3N
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Write the half-reactions
Zn + 2HCl  ZnCl2 + H2
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Balancing Redox Rxns
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Balancing Redox Rxns (Cont.)
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Balance the Redox Reaction
Na + Fe+3  Na+ + Fe0
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Balance the Redox Reaction
Ca0 + Al+3  Ca+2 + Al0
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Balance the Redox Reaction
Au0 + H+1  Au+3 + H20
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How do you get good at this?
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And how do you get even better?
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A Few Key Points
1. Chemical reactions can produce electrical energy (i.e. “a stream of electrons”).
2. The loss of electrons (oxidation) from one atom must occur with a gain of electrons
to another (reduction).
3. In any chemical reaction, mass, energy and charge must be conserved.
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Unit 12: Electrochemistry
Lesson 2: Electrochemistry
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It’s all about activity
Not all metals are created equal.
Some metals are oxidized more easily than others.
Reference Table J lists a bunch of metals according to how easily they will be oxidized.
What is the most easily oxidized metal?
What is the most difficult metal to oxidize.
Note: Table J also has the most easily reduced non-metals!
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Fun With Table J
Which Reaction is more likely to occur:
1. Cu+2 + Al0  Cu0 + Al+3
2. Cu0 + Al+3  Cu+2 + Al0
Why?
Which Reaction is more likely to occur:
1. Cl20 + 2F-1  2Cl- + F20
2. F2 + 2Cl-1  2F- + Cl20
Why?
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Spontaneous Redox Reactions
Batteries are spontaneous redox reactions (they wouldn’t be very useful if they
weren’t).
Voltage:
A measurement of the force that moves electrons through a circuit.
To see if a redox reaction is spontaneous, we will need to determine the overall
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