Transcript Document

Displacement reactions
Acid-Base reactions
recombine ions
H+ transfer
Fe2O3 (s) + Al (s)  Al2O3 (s) + Fe(l)
thermite reaction
Oxidation-Reduction reactions (redox) e- transfer
Fe2O3 = iron (III )oxide Fe3+ Fe (l) = Fe0
26 protons
Fe0 has _____
Fe3+ has_____
26 protons
Fe3+ has ____
23 electrons
26 electrons
Fe0 has ____
Fe3+ gained 3 electrons
reducing the oxidation state
gaining e- = reduction
3+  0
Fe2O3 (s) + Al (s)  Al2O3 (s) + Fe(l)
Al (s) = Al0
Al2O3 aluminum oxide
Al0 has _____
13 electrons
oxidation state = 0
Al0 loses___
3 elosing e- = oxidation
LEO
GER
10 electrons
Al3+has ______
oxidation state = 3+
increase oxidation number
0  3+
Lose Electrons Oxidation
Gain Electrons Reduction
Rules for oxidation numbers
1. Oxidation number for elements is zero.
N2,O2, Na(s), Co(s), He (g)
2. Oxidation number of monatomic ions
is the same as their charge
Group IA = +1 Al3+, Zn2+, Cd2+, Ag+
Group IIA = +2
3. Oxidation number of oxygen in most compounds
is –2. Exceptions: H2O2, O2- (peroxides) –1
4. Oxidation number of hydrogen is +1
Exceptions: bonded to metals LiH
5. Fluorine is always –1. Other halogens are –1.
Exceptions: bonded to O, they are positive
Assign oxidation numbers to all of the elements:
Li2O
Li = +1
O = -2
PF3
P = +3
F = -1
HNO3 H = +1
N = +5
MnO4-
Mn = +7 O = -2
Cr2O72- Cr = +6 O = -2
O = -2
What is the oxidation state of the highlighted element?
P2O5
+5
diphosphorous pentoxide
NaH
-1
sodium hydride
SnBr4
+4
tin (IV) bromide
BaO2
-1
barium peroxide
Redox reactions
0
+1
0
+2
Zn (s) + 2H+ (aq)  H2 (g) + Zn2+
Zn
0  +2
increase oxidation state
lose electrons
oxidized
reducing agent
H
+1  0
decrease oxidation state
gain electrons
reduced
oxidizing agent
0
0
+1 -2
2H2(g) + O2 (g)  2H2O(l)
H loses or gains electrons
is oxidized or reduced
oxidizing or reducing agent
O loses or gains electrons
is oxidized or reduced
oxidizing or reducing agent
0
+7
+3
+4
2H2O + Al(s) + MnO4-  Al(OH)4- + MnO2
What is being oxidized?
What is oxidation?
LEO
How many e-?
H2O
Al
MnO4Al(OH)4MnO2
What is being reduced?
GER
What is the reducing agent?
What is the oxidation state of S in each of these
compounds:
H 2S
S = -2 H = +1
S8
S=0
SCl2
S = +2
Cl = -1
Na2SO3 S = +4
O = -2
SO42-
Na = +1
S = +6 O = -2
Which of these compounds can not act as a
reducing agent?
Which of these compounds can not act as a
oxidizing agent?
0
+4 -2 +1 -2 +2 -2 +1 +2 -2 +1
Cd(s) + NiO2 + 2H2O  Cd(OH)2 + Ni(OH)2
What is being oxidized?
What is being reduced?
What is the oxidizing agent?
What is the reducing agent?
How many electrons are transferred?