Oxidation & Reduction
Monday 3/3/08
Prep:
1.
Submit 20-1 & 20-2 for copies.
2.
Clean up room.
Class:
DMA: Set all lab equipment on side counters. Schedule of Week
(Pass papers while graphs checked)
1.
Graphs shared up front for discussion of results using document
viewer.
2.
Lab report expectations reviewed.
Asmt: Lab Report (written individually) due Tuesday.
Plan:
1.
Talk to POD about Rubric & Thursday.
2.
Respond to tournament query.
3.
Explore U12 & U11 brackets.
Schedule of Week 3/3-3/7/08
Mon – Review Lab Results / Asmt:
INDIVIDUAL Lab Report due Tuesday
Tues – Oxidation / Reduction / Worksheet
20-1 / Asmt: Page 665 #1-4, 669 #1-3
Wed – Analyzing Reactions / Worksheet 202 / Asmt: Practice Exam 4
Thur – Review Unit 4
Fri – Unit 4 Exam (no school?)
Redox
• Side 8 Chapter 20 Voltaic Cells –
Oxidation vs Reduction  Electricity!
• Chapter 23 Electrolytic Cells – Redox to
Isolate Metals!
• Electrolysis of Water Demo
• Chapter 36 The Dry Cell?
• Chapter 10 Space Flight
Oxidation Numbers – 6 Rules
1.
2.
3.
The oxidation # of a lone element is 0.
The oxidation # of a monatomic ion = its ionic charge.
Periodic patterns of elements include:
•
•
•
•
•
4.
5.
6.
Alkali metals = +1
alkaline earth metals = +2,
Al is always +3, F is always -1,
H is +1 if with non-metals,
O is almost always -2.
Every element in a compound has an oxidation # for
each atom.
The total of all the oxidation #s in a compound = 0.
The total oxidation #s in a polyatomic ion = the total
charge.
20-1 Examples
1. N2
• Ox# = 0
2. H2O
• Ox#s: H: +1, O: -2
3. NaCl
• Ox#s: Na: +1, Cl: -1
4. OH-1
• Ox#s: O: -2, H: +1
• Total: -2 +1 = -1
5.
•
6.
•
•
7.
•
•
•
Fe
Ox# = 0
Fe2O3
Ox#s: O: -2 (x3) = -6
Fe +3 (x2)=+6
BaSO4
Ox#s: Ba: +2,
O: -2 (x4) = -8
S must be -6 to make
total = 0
Definitions
•
•
•
•
Oxidation – loss of electrons (LEO)
Reduction – gain of electrons (GER)
LEO says GER!
Loss of Electrons is Oxidation, Gain of
Electrons is Reduction
• Oxidizing Agent – Gains electrons to leave
victim oxidized. (= electron thief)
• Reducing Agent – Donates electrons ands
becomes oxidized (= victim).
Al is the reducing agent
20-2 Example 1
Al was the victim
Al lost 3 electrons
Al
0
+
0
O2
Al was oxidized

+3(x2) -2 (x3)
Al2O3
O gained 2 electrons
O was the thief!
O was reduced
O is the oxidizing agent
a. Determine all oxidation numbers:
b. Determine what became more positive since it
lost electrons (oxidized) & what became more
negative since it gained electrons (reduced).
c. Determine which was the thief (oxidizing
agent) & which was the victim (reducing
agent).
Fe is the reducing agent
Fe was the victim
20-2 Example 2
Fe lost 2 electrons
Fe
0
+
+2
Fe was oxidized
-1 (x2)
CuCl2

+2
FeCl2
Cu gained 2 electrons
Cu was the thief!
-1 (x2)
+
Cu
0
Cu was reduced
Cu is the oxidizing agent
a. Determine all oxidation numbers:
b. Determine what became more positive since it
lost electrons (oxidized) & what became more
negative since it gained electrons (reduced).
c. Determine which was the thief (oxidizing
agent) & which was the victim (reducing
agent).