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Chapter 6, Activity 8. “Oxidation-Reduction Reactions”. LEO SAYS GER. Activity 8 The Meaning of Oxidation and Reduction (called “ redox ”). OBJECTIVES Define oxidation and reduction in terms of the loss or gain of oxygen, and the loss or gain of electrons.

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Chapter 6, Activity 8

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Chapter 6 activity 8

Chapter 6, Activity 8

“Oxidation-Reduction Reactions”


Activity 8 the meaning of oxidation and reduction called redox

Activity 8The Meaning of Oxidation and Reduction (called “redox”)


    • Define oxidation and reduction in terms of the loss or gain of oxygen, and the loss or gain of electrons.

Activity 8 the meaning of oxidation and reduction redox

Activity 8The Meaning of Oxidation and Reduction (Redox)


    • State the characteristics of a redox reaction and identify the oxidizing agent and reducing agent.

Activity 8 the meaning of oxidation and reduction redox1

Activity 8The Meaning of Oxidation and Reduction (Redox)


    • Describe what happens to iron and other metals when they corrode.

Oxidation and reduction redox

Oxidation and Reduction (Redox)

  • Early chemists saw “oxidation” reactions only as the combination of a material with oxygen to produce an oxide.

    • For example, when methane burns in air, it oxidizes and forms oxides of carbon and hydrogen

Oxidation and reduction redox1

Oxidation and Reduction (Redox)

  • But, not all oxidation processes that use oxygen involve burning:

    • Elemental iron slowly oxidizes to compounds such as iron (III) oxide, commonly called “rust”

    • Hydrogen peroxide also releases oxygen when it decomposes

Oxidation and reduction redox2

Oxidation and Reduction (Redox)

  • A process called “reduction” is the opposite of oxidation, and originally meant the loss of oxygen from a compound

  • Oxidation and reduction always occur simultaneously

  • The substance gaining oxygen (or losing electrons) is oxidized, while the substance losing oxygen (or gaining electrons) is reduced.

Memory aids


  • LEO the lion goes GER

    • Loss of electrons is oxidation

    • Gain of electrons is reduction


    • Oxidation is loss

    • Reduction is gain

Oxidation and reduction redox3

Oxidation and Reduction (Redox)

Each sodium atom loses one electron:

Each chlorine atom gains one electron:

Leo says ger

LEO says GER :

Lose Electrons = Oxidation

Sodium is oxidized

Gain Electrons = Reduction

Chlorine is reduced

Leo says ger1

LEO says GER :

- Losing electrons is oxidation, and the substance that loses the electrons is called the reducing agent.

- Gaining electrons is reduction, and the substance that gains the electrons is called the oxidizing agent.

Mg(s) + S(s) → MgS(s)

Mg is oxidized: loses e-, becomes a Mg2+ ion

Mg is the reducing agent

S is the oxidizing agent

S is reduced: gains e- = S2- ion

Not all reactions are redox reactions

Not All Reactions are Redox Reactions

- Reactions in which there has been no change in oxidation number are NOT redox reactions.




  • Damage done to metal is costly to prevent and repair

  • Iron, a common construction metal often used in forming steel alloys, corrodes by being oxidized to ions of iron by oxygen.

    • This corrosion is even faster in the presence of salts and acids, because these materials make electrically conductive solutions that make electron transfer easy



  • Luckily, not all metals corrode easily

    • Gold and platinum are called noble metals because they are resistant to losing their electrons by corrosion

    • Other metals may lose their electrons easily, but are protected from corrosion by the oxide coating on their surface, such as aluminum

    • Iron has an oxide coating, but it is not tightly packed, so water and air can penetrate it easily



  • Serious problems can result if bridges, storage tanks, or hulls of ships corrode

    • Can be prevented by a coating of oil, paint, plastic, or another metal

    • If this surface is scratched or worn away, the protection is lost

  • Other methods of prevention involve the “sacrifice” of one metal to save the second

    • Magnesium, chromium, or even zinc (called galvanized) coatings can be applied

Trends in oxidation and reduction

Trends in Oxidation and Reduction

  • Active metals:

    • Lose electrons easily

    • Are easily oxidized

    • Are strong reducing agents

  • Active nonmetals:

    • Gain electrons easily

    • Are easily reduced

    • Are strong oxidizing agents

Identifying redox equations

Identifying Redox Equations

  • In general, all chemical reactions can be assigned to one of two classes:

    • oxidation-reduction, in which electrons are transferred:

      • Single-replacement, synthesis, decomposition, and combustion

    • this second class has no electron transfer, and includes all others:

      • Double-replacement and acid-base reactions

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