Transcript Document

Oxidizing & Reducing
Agents
Oxidizing Agents  An oxidizing agent, or
oxidant, gains electrons and is reduced in
a chemical reaction.
Reducing Agents  A reducing agent, or
reductant, loses electrons and is oxidized
in a chemical reaction.
oxidized
reduced
0
+2 -2
0
Mg(s) + S(s)  Mg S(s)
Reducing
Agent
Oxidizing
Agent
GER
Gains
Electrons
Reduction
LEO
Loses
Electrons
Oxidation
rOAR
Oxidizing
Agent
Reduced
Reference
Table J
Oxidizes –
Reducing
Agent
Reduces –
Oxidizing
Agent
Fe vs. Cu
Fe
Cu
Mn vs. Co
Mn
Co
Br2 vs. I2
I2
Br2
How to Identify Reducing and
Oxidizing Agents
Cl2 (aq) + 2 Br- (aq)  2 Cl- (aq) + Br2 (aq)
Oxidation:
2 Br- (aq)  Br2 (aq)
Oxidation States: -1
0
Reduction:
Cl2 (aq)  2 Cl- (aq)
Oxidation States: 0
-1
* Br- loses an electron; it is oxidized from Br- to
Br2. Br- is the reducing agent.
* Cl2 gains one electron; it is reduced from Cl2
to 2 Cl-. Cl2 is the oxidizing agent.
Oxidizing Reducing
Agents
Agents
Oxidation Decreases Increases
State
# of
Gained
Lost
Electrons
Substance Reduced Oxidized
is
Learning Check:
Which are the oxidizing and reducing agents?
Pb + NaNO3  PbO + NaNO2
0
+1 +5 -2
+2 -2
+1 +3 -2
Pb loses 2e- to become Pb+2, so it is oxidized.
N+5 gains 2e- to become N+3, so it is reduced.
Calculating Potentials
Chart on p. 469 shows reduction potentials
*For oxidation: reverse rxn, change the sign
What is the maximum voltage that can be
obtained from an electrochemical cell with
Zn/Zn2+ and Cu/Cu2+?
Use Table J to see which oxidizes or reduces.
Zn oxidizes, Cu reduces
Reduces: Cu2+ + 2e-  Cu
0.34 V
Oxidizes: Zn  Zn2+ + 2e0.76 V
1.10 V
** Positive voltage = spontaneous
Learning Check:
Using the table of standard potentials (p. 469),
calculate the theoretical voltage.
Cu/Cu2+ and Mg/Mg2+
Oxidation: Mg  Mg2+ + 2eReduction: Cu2+ + 2e-  Cu
Mg/Mg2+ and Zn/Zn2+
Oxidation: Mg  Mg2+ + 2eReduction: Zn2+ + 2e-  Zn
2.37 V
0.34 V
2.7 V
2.37 V
- 0.76 V
1.6 V