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Oxidation–Reduction Reactions

Electrochemistry-1

By: Dr. Munawar Hussain

Chemistry at Work

Everyday Oxidation-Reduction

Reactions

An oxidation–reduction reaction

provides us with energy from food

provides electrical energy in batteries

occurs when iron rusts

4Fe(s) + 3O2(g) 2Fe2O3(s)

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Transfer of Electrons

An oxidation–reduction reaction

transfers electrons from one reactant to another

Oxidation Is a Loss of electrons (OIL)

Zn(s) Zn2+(aq) + 2e

Reduction Is a Gain of electrons (RIG)

Cu2+(aq) + 2e Cu(s)

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Oxidation and Reduction

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Oxidized or Reduced?

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Zn and Cu2+

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oxidation

Zn(s) Zn2+(aq) + 2e-

Silvery metal

reduction

Cu2+(aq) + 2e- Cu(s)

Electron Transfer from Zn to

Cu2+

Oxidation: electron loss

Reduction: electron gain

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Learning Check

Identify each of the following as:

1) oxidation or 2) reduction

A. Sn(s) Sn4+(aq) + 4e−

B. Fe3+(aq) + 1e− Fe2+(aq)

C. Cl2(g) + 2e− 2Cl−(aq)

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Solution

Identify each of the following as:

1) oxidation or 2) reduction

1 A. Sn(s) Sn4+(aq) + 4e−

2 B. Fe3+(aq) + 1e− Fe2+(aq)

2 C. Cl2(g) + 2e− 2Cl−(aq)

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Writing Oxidation and

Reduction Reactions Write the separate oxidation and reduction reactions

for the following equation.

2Cs(s) + F2(g) 2CsF(s)

Each cesium atom loses an electron to form a cesium ion.

2Cs(s) 2Cs+(s) + 2e− oxidation

Each fluorine atom gains an electron to form a fluoride ion.

F2(s) + 2e– 2F−(s) reduction

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Learning Check

In light-sensitive sunglasses, UV light initiates an

oxidation–reduction reaction.

uv light

Ag+ + Cl− Ag + Cl

A. Which reactant is oxidized?

B. Which reactant is reduced?

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Solution

In light-sensitive sunglasses, UV light initiates an oxidation-reduction reaction.

uv light

Ag+ + Cl− Ag + Cl

A. Which reactant is oxidized?

Cl − Cl− Cl + 1e−

B. Which reactant is reduced?

Ag+ Ag+ + 1e− Ag

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Learning Check

Identify the substances that are oxidized and

reduced in

each of the following reactions:

A. Mg(s) + 2H+(aq) Mg2+(aq) + H2(g)

B. 2Al(s) + 3Br2(g) 2AlBr3(s)

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Solution

Identify the substances that are oxidized and reduced in

each of the following reactions:

A. Mg is oxidized Mg(s) Mg2+(aq) + 2e−

H+ is reduced 2H+ + 2e− H2

B. Al is oxidized 2Al 2Al3+ + 6e−

Br is reduced 2Br + 2e− 2Br−

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Oxidation–Reduction in

Biological Systems

In biological systems, oxidation may involve

the loss of H

the gain of O

In biological systems, reduction may involve

the gain of H

the loss of O

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Oxidation–Reduction in Biological Systems

(continued)

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Summary of Oxidation and

Reduction

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