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Wize University Chemistry Textbook > Chemical Reactions

Reduction-Oxidation (Redox) Reactions

Oxidation StatesPrevious Section
Balancing Redox Reactions [half-reaction method]Next Section
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Redox Reactions

OIL RIG! Oxidation Is Loss of electrons, Reduction Is Gain of electrons
OR
LEO GER! Loss of Electrons is Oxidation, Gain of Electrons is Reduction

OXIDATION (lose e-) REDUCTION (gain e−)

_____________

Reducing agent reduces others and is itself Oxidizing agent oxidizes others and is itself
oxidized. reduced.

Oxidation number increases. Oxidation number is reduced.


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Keep in mind that in organic chemistry the definitions of oxidation and reduction are different:
  • For reduction, we would look for more bonds to H and less bonds to O
  • For oxidation, we would look for less bonds to H and more bonds to O!


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How can you recognize if a redox reaction is occuring?

1. Can check oxidation #s of each element to see if they change from reactants to products (most important for now!)

2. Familiarize yourself with common oxidizing and reducing agents (you'll learn more about this in orgo!)
  • Oxidizing agents: O2, halogens, HNO3, Cr2O72-, MnO4-
  • Reducing agents: H2, metals, C



Practice: Oxidation vs Reduction

Consider the following balanced redox equation:
16H(aq)++2MnO4(aq)−+10Cl(aq)−→2Mn(aq)2++5Cl2(g)+8H2O(l)16H^+_{(aq)}+2MnO^-_{4(aq)}+10Cl^-_{(aq)} \to 2Mn^{2+}_{(aq)}+5Cl_{2(g)}+8H_2O_{(l)}
Which species is being oxidized?

Practice: Oxidizing vs Reducing Agent

Consider the following balanced redox equation:
16H(aq)++2MnO4(aq)−+10Cl(aq)−→2Mn(aq)2++5Cl2(g)+8H2O(l)16H^+_{(aq)}+2MnO^-_{4(aq)}+10Cl^-_{(aq)} \to 2Mn^{2+}_{(aq)}+5Cl_{2(g)}+8H_2O_{(l)}
Which species is the reducing agent?

Practice: Oxidizing vs Reducing Agents

What is the reducing agent in the following chemical reaction?

NO + Au+ → NO3- + Au
Extra Practice
Consider the following balanced redox equation:
16H(aq)++2MnO4(aq)−+10Cl(aq)−→2Mn(aq)2++5Cl2(g)+8H2O(l)16H^+_{(aq)}+2MnO^-_{4(aq)}+10Cl^-_{(aq)} \to 2Mn^{2+}_{(aq)}+5Cl_{2(g)}+8H_2O_{(l)}
Which species is the reducing agent?
Consider the following balanced redox equation:
16H(aq)++2MnO4(aq)−+10Cl(aq)−→2Mn(aq)2++5Cl2(g)+8H2O(l)16H^+_{(aq)}+2MnO^-_{4(aq)}+10Cl^-_{(aq)} \to 2Mn^{2+}_{(aq)}+5Cl_{2(g)}+8H_2O_{(l)}
Which species is the oxidizing agent?
Consider the following balanced redox equation:
16H(aq)++2MnO4(aq)−+10Cl(aq)−→2Mn(aq)2++5Cl2(g)+8H2O(l)16H^+_{(aq)}+2MnO^-_{4(aq)}+10Cl^-_{(aq)} \to 2Mn^{2+}_{(aq)}+5Cl_{2(g)}+8H_2O_{(l)}
Which species is being oxidized?
Electrochemistry: Galvanic Cells
The cell pictured below is prepared under standard conditions. In this cell, what will be the anode?
𝐶𝑢2+(𝑎𝑞)+𝐻2(𝑔)⇌𝐶𝑢(𝑠)+2𝐻+(𝑎𝑞)𝐸°=0.339𝑉𝐶𝑢^{2+} (𝑎𝑞)+𝐻_2 (𝑔)\rightleftharpoons 𝐶𝑢 (𝑠)+2 𝐻^+ (𝑎𝑞) \qquad𝐸°=0.339 𝑉
Electrochemistry: Redox
Consider the following balanced redox equation:
16H(aq)++2MnO4(aq)−+10Cl(aq)−→2Mn(aq)2++5Cl2(g)+8H2O(l)16H^+_{(aq)}+2MnO^-_{4(aq)}+10Cl^-_{(aq)} \to 2Mn^{2+}_{(aq)}+5Cl_{2(g)}+8H_2O_{(l)}
Which species is the reducing agent?
What is the oxidizing agent in the following reaction?
2 As(s) + 3 Cl2(g) --> 2 AsCl3
What is being oxidized in the following reaction?
Cr+ + Sn4+ --> Cr3+ + Sn2+
Oxidation is the __________ of __________
Reduction is the __________ of __________