Objective: To identify the oxidizing and reducing agents in a
redox reaction.
Oxidizing Agent: a substance which takes electrons from a substance
that is being oxidized.
Oxidizing
agents are electron prowlers.
Oxidizing agents contain an atom with a relatively
high oxidation number.
The
atom in an oxidizing agent is always reduced.
Examples of substances that often (not
always) act as oxidizing agents:
|
Common oxidizing agent |
Element with relatively high oxidation number |
|
H2O2 ( peroxide) |
O = -1 , high because O is normally -2 |
|
MnO4-1 |
Mn = 7, high because Mn is often <7 |
|
O2 |
O = 0, high because O is normally -2 |
|
Br2 |
Br = 0, because Br is normally -1 |
|
NO3-1 |
N = 5, because N is often 0 or -3 |
|
Ag+1 |
Ag = 1, because Ag is commonly 0 |
Reducing Agent: a substance which gives electrons to a
substance that is being reduced.
Reducing agents contain an atom with a
relatively low oxidation number.
The atom in a reducing agent is always oxidized
Examples of substances that often (not
always) act as reducing agents:
|
Common reducing agent |
Element with relatively low oxidation number |
|
Li |
Li = 0 (normally +1 --when part of compound, of course) |
|
Ca |
Ca = 0 (normally +2) |
|
Al |
Al = 0 (normally +3) |
|
Zn |
Zn = 0 (normally +2) |
|
LiAlH4 ( metal hydride) |
H = -1 (normally +1) |
|
H2 |
H= 0 (normally +1) |
|
HSO3-1 |
S = 4 (could be +6 when part of sulfate) |
Examples :
Identify the oxidizing and reducing agents in the following:
1. Fe
+ Cu+2 à Fe+2 + Cu
Fe = getting oxidized so it is a reducing agent
Cu+2 = getting reduced,
so it is the electron-mugger or oxidizing agent
2. 2 Na + Cl2 à 2 NaCl
Na = getting oxidized so it is a
reducing agent
Cl2 = getting reduced,
so it is the electron-mugger or oxidizing agent
3. H2O2 + SO2
à SO4-2
+ 2H+1
SO2 = the S in it is
getting oxidized, so SO2 is a reducing agent
H2O2 = the O
is getting reduced from -1 to -2, so it is the electron-mugger or oxidizing
agent
4. Ga + I2
à Ga+3 + I-1
Ga = the Ga is
getting oxidized, so Ga is a reducing agent
I2 = Each I is getting
reduced from 0 to -1, so I2 is the electron-mugger or oxidizing
agent
Exercises for Objective D
1. Identify the oxidizing and reducing agents
in the following:
2. Balance using balanced half
reactions in an acidic medium.