Oxidizing & ReducingOxidizing & ReducingAgentsAgents

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.

Mg(s) + S(s) Mg S(s)

0 0 +2 -2

Reducing Agent

OxidizingAgent

oxidized reduced

LEOLoses Electrons Oxidation

GERGains Electrons Reduction

rOAROxidizing Agent Reduced

Reference Reference Table JTable 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                   0Reduction: 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 Agents

Reducing Agents

Oxidation State

Decreases Increases

# of Electrons

Gained Lost

Substance is

Reduced Oxidized

Learning Check:

Which are the oxidizing and reducing agents?

Pb + NaNO3 PbO + NaNO2

Pb loses 2e- to become Pb+2, so it is oxidized.N+5 gains 2e- to become N+3, so it is reduced.

0 +1 +5 -2 +2 -2 +1 +3 -2

Calculating PotentialsCalculating PotentialsChart 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 reducesReduces: Cu2+ + 2e- Cu 0.34 VOxidizes: Zn Zn2+ + 2e- 0.76 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+ + 2e- 2.37 VReduction: Cu2+ + 2e- Cu 0.34 V

2.7 V

Mg/Mg2+ and Zn/Zn2+

Oxidation: Mg Mg2+ + 2e- 2.37 VReduction: Zn2+ + 2e- Zn - 0.76 V

1.6 V