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Chapter 15 Oxidation-Reduction: Transfer of Electrons

15.1 Oxidation and Reduction

Rust forms on a set of tools when oxygen reacts with iron.

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Oxidation and Reduction

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) Rust forms on a set of tools when oxygen reacts with iron.

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In an oxidation-reduction reaction, one reactant loses electrons and another reactant gains electrons.• electrons are transferred from one reactant to

another• oxidation is a loss of electrons (oil)

Zn(s) Zn2+(aq)+ 2 e (loss of electrons)• reduction is a gain of electrons (rig)

Cu2+(aq) + 2 e Cu(s) (gain of electrons)

Electron Loss and Gain

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Examples of Oxidized and Reduced Substances

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Zn and Cu2+

In a single replacement reaction,• Zn(s) is oxidized to Zn2+(aq)

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

• Cu2+(aq) is reduced to Cu(s) Cu2+(aq) + 2 e Cu(s)• The overall equation is written Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s)

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Electron Transfer from Zn to Cu2+

Oxidation of Zn: electron loss

Reduction of Cu2+: electron gain

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Identify each of the following as (O) oxidation or (R) reduction:

__A. Sn(s) Sn4+(aq) + 4 e

__B. Fe3+(aq) + 1 e Fe2+(aq)

__C. Cl2(g) + 2 e 2Cl(aq)

Learning Check

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Solution

O A. Sn(s) Sn4+(aq) + 4 e

R B. Fe3+(aq) + 1 e Fe2+(aq)

R C. Cl2(g) + 2 e 2Cl(aq)

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Write the oxidation reaction and the reduction reaction for the following: 2Cs(s) + F2(g) 2CsF(aq)

Learning Check

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Write the oxidation reaction and the reduction reaction for the following:2Cs (s) + F2(g) 2CsF(aq)

oxidation Cs(s) Cs+(aq) + 1 e reduction F2(g) + 2 e 2F−(aq)

Solution

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In light-sensitive sunglasses, light initiatesan oxidation-reduction reaction. light

Ag+(aq) + Cl−(aq) Ag(s) + Cl(s)

A. Which reactant is oxidized?

B. Which reactant is reduced?

Learning Check

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In light-sensitive sunglasses, light initiatesan oxidation-reduction reaction. light

Ag+(aq) + Cl−(aq) Ag(s) + Cl(s)

A. Which reactant is oxidized? Cl−(aq) Cl(s) + 1 e

B. Which reactant is reduced? Ag+(aq) + 1 e− Ag(s)

Solution