Oxidation and Reduction

Oxidation The chemical process by which an element or compound gains oxygen. Example: 2Mg(s) + O 2  2MgO Example: 2Mg(s) + O 2  2MgO Oxidation naturally happens to every metal except platinum and gold. Oxidation naturally happens to every metal except platinum and gold. Oxidation can also be applied to any element or compound which gives up electrons in order to form a covalent or ionic compounds. Oxidation can also be applied to any element or compound which gives up electrons in order to form a covalent or ionic compounds. Example: Cu(s)  Cu e- Example: Cu(s)  Cu e-

Fe + O 2  Fe 2 O 3 Ag + O 2  Ag 2 O

Oxygen cause food to spoil by oxidation!

Reduction The chemical process by which an element or compound loses oxygen. The chemical process by which an element or compound loses oxygen. This is how metal is refined. The oxygen is removed in order to “reduce” metals to their elemental form. This is how metal is refined. The oxygen is removed in order to “reduce” metals to their elemental form. Example: 2 ZnO  2 Zn + O 2 Example: 2 ZnO  2 Zn + O 2 Reduction is also applied to any element or compound which gains electrons in order to form a covalent or ionic compounds. Reduction is also applied to any element or compound which gains electrons in order to form a covalent or ionic compounds. Example: Fe e-  Fe Example: Fe e-  Fe

Redox This is the name given to any reaction that involves a gain of electrons by one compound and loss of electrons by another. This is the name given to any reaction that involves a gain of electrons by one compound and loss of electrons by another. An easy way to remember which is to think of LEO the Lion: An easy way to remember which is to think of LEO the Lion: LEO the lion says “GER” LEO the lion says “GER” Lose Electrons— Oxidation Lose Electrons— Oxidation Gain Electrons— Reduction Gain Electrons— Reduction You can recognize a redox reaction by assigning oxidation numbers to each element in each compound and look to see if they change from the reactant side to the product side.

Example 1: Example 1: Assign oxidation numbers first! Assign oxidation numbers first! CuCl 2 + Zn  ZnCl 2 + Cu CuCl 2 + Zn  ZnCl 2 + Cu Species oxidized? ______ Species oxidized? ______ –Loses electrons - Zn 0 to Zn 2+ Species reduced? ______ Species reduced? ______ –Gains electrons - Cu 2+ to Cu 0 Zn Cu 2+

Example 2: Example 2: CuO + C  Cu + CO 2 2CuO + C  Cu + CO 2 Species oxidized? ______ Species oxidized? ______ –Loses electrons - C 0 to C +4 Species reduced? ______ Species reduced? ______ –Gains electrons – Cu +2 to Cu 0 C Cu 2+

Oxidizing Agent Oxidizing Agent a substance that can cause another substance to be oxidized (lose electrons) a substance that can cause another substance to be oxidized (lose electrons) Strong oxidizing agents are those that want to gain electrons the most, such as Fluorine, oxygen and Chlorine. (they are electron hungry!) Strong oxidizing agents are those that want to gain electrons the most, such as Fluorine, oxygen and Chlorine. (they are electron hungry!) They are the substance that gets reduced! They are the substance that gets reduced! Reducing Agent Reducing Agent a substance that can cause another substance to be reduced (gain electrons) a substance that can cause another substance to be reduced (gain electrons) Strong reducing agents are those that easily give up electrons, such as Na, Li and K Strong reducing agents are those that easily give up electrons, such as Na, Li and K They are the substance that gets oxidized! They are the substance that gets oxidized!

Example Cl 2 + 2Br 1- (aq)  2Cl 1- (aq) + Br 2 Cl 2 + 2Br 1- (aq)  2Cl 1- (aq) + Br 2 Species Oxidized = Species Oxidized = Species Reduced = Species Reduced = Oxidizing agent = Oxidizing agent = Reducing agent = Reducing agent = Loses electrons = Br 1- Gains electrons = Cl 2 Cl 2 Br 1-