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 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 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 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 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.