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Oxidation-Reduction Reactions “Redox”

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Presentation on theme: "Oxidation-Reduction Reactions “Redox”"— Presentation transcript:

1 Oxidation-Reduction Reactions “Redox”

2 Oxidation and Reduction (Redox)
Electrons are transferred Spontaneous redox rxns can transfer energy Electrons (electricity) Heat Non-spontaneous redox rxns can be made to happen with electricity

3 Oxidation Reduction Reactions (Redox)
Each sodium atom loses one electron: Each chlorine atom gains one electron:

4 LEO says GER : Lose Electrons = Oxidation Sodium is oxidized Gain Electrons = Reduction Chlorine is reduced

5 Not All Reactions are Redox Reactions
Reactions in which there has been no change in oxidation number are not redox rxns. Examples:

6 Rules for Assigning Oxidation Numbers Rules 1 & 2
The oxidation number of any uncombined element is zero 2. The oxidation number of a monatomic ion equals its charge

7 Rules for Assigning Oxidation Numbers Rules 3 & 4
3. The oxidation number of oxygen in compounds is -2 4. The oxidation number of hydrogen in compounds is +1

8 Rules for Assigning Oxidation Number Rule 5
5. The sum of the oxidation numbers in the formula of a compound is 0 2(+1) + (-2) = 0 H O (+2) + 2(-2) + 2(+1) = 0 Ca O H

9 Rules for Assigning Oxidation Numbers Rule 6
6. The sum of the oxidation numbers in the formula of a polyatomic ion is equal to its charge X + 4(-2) = -2 S O X + 3(-2) = -1 N O  X = +5  X = +6

10 The Oxidation Number Rules - SIMPLIFIED
1. The sum of the oxidation numbers in ANYTHING is equal to its charge 2. Hydrogen in compounds is +1 3. Oxygen in compounds is -2

11 Reducing Agents and Oxidizing Agents
The substance reduced is the oxidizing agent The substance oxidized is the reducing agent Sodium is oxidized – it is the reducing agent Chlorine is reduced – it is the oxidizing agent

12 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

13 Redox Reaction Prediction #1
Important Oxidizers Formed in reaction MnO4- (acid solution) MnO4- (basic solution) MnO2 (acid solution) Cr2O72- (acid) CrO42- HNO3, concentrated HNO3, dilute H2SO4, hot conc Metallic Ions Free Halogens HClO4 Na2O2 H2O2 Mn(II) MnO2 Cr(III) NO2 NO SO2 Metallous Ions Halide ions Cl- OH- O2

14 Redox Reaction Prediction #2
Important Reducers Formed in reaction Halide Ions Free Metals Metalous Ions Nitrite Ions Sulfite Ions Free Halogens (dil, basic sol) Free Halogens (conc, basic sol) C2O42- Halogens Metal Ions Metallic ions Nitrate Ions SO42- Hypohalite ions Halate ions CO2

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