4.3 Redox Reactions

• Oxidation and reduction always occur together in a redox reaction.


  True
• In the reaction Fe + O₂ → Fe₂O₃, oxygen acts as the reducing agent.

  False
• In the final step of balancing a redox equation, any common terms such as electrons and H₂O must be canceled out.

  True
• Oxidation and reduction processes in a redox reaction result in a transfer of electrons between substances.


  True
• In a redox reaction, the reducing agent becomes oxidized itself while causing the other substance to become reduced
• An oxidizing agent accepts electrons.


  True
• An oxidizing agent becomes reduced itself during a redox reaction.

  True
• Steps to balance a redox equation using the half-equation method:

  1️⃣ Identify half-equations

  2️⃣ Balance elements except oxygen and hydrogen

  3️⃣ Balance oxygen by adding H₂O

  4️⃣ Balance hydrogen by adding H⁺

  5️⃣ Balance charge by adding electrons (e⁻)

  6️⃣ Equalize electron numbers

  7️⃣ Combine half-equations and check balance
• The balanced redox equation for MnO₄⁻ + Fe²⁺ → Mn²⁺ + Fe³⁺ is 5Fe²⁺ + 8H⁺ + MnO₄⁻ → 5Fe³⁺ + Mn²⁺ + 4H₂O
• Electron transfer involves the gain and loss of electrons between reactants.


  True
• What is the balanced redox equation for the extraction of iron from iron oxide using carbon monoxide?

  Fe₂O₃ + 3CO → 2Fe + 3CO₂
• What is the definition of oxidation in a redox reaction?

  Loss of electrons
• What is the role of a reducing agent in a redox reaction?

  Donates electrons
• How is oxygen balanced in a half-equation?

  By adding H₂O
• What happens to the charge of a substance when it undergoes oxidation?

  Becomes more positive
• What is the role of an oxidizing agent in a redox reaction?

  Accepts electrons
• In a redox reaction, substances act as either oxidizing or reducing agents
• A reducing agent donates electrons
• Match the role in a redox reaction with the corresponding characteristic:

  Oxidizing agent ↔️ Causes reduction of other substances

  Reducing agent ↔️ Causes oxidation of other substances
• What is the balanced redox equation for the reaction MnO₄⁻ + Fe²⁺ → Mn²⁺ + Fe³⁺?

  5Fe²⁺ + 8H⁺ + MnO₄⁻ → 5Fe³⁺ + Mn²⁺ + 4H₂O
• In the reaction 2Na + Cl₂ → 2NaCl, which substance is oxidized?

  Sodium (Na)
• Iron is extracted from iron oxide (Fe₂O₃) by reducing it with carbon monoxide
• The substance that causes oxidation in a redox reaction is called the oxidizing agent
• Steps to balance a redox equation using the half-equation method

  1️⃣ Identify oxidation and reduction half-equations

  2️⃣ Balance each half-equation separately

  3️⃣ Equalize electron numbers

  4️⃣ Combine half-equations

  5️⃣ Check the balance
• In the half-equation Fe²⁺ → Fe³⁺ + e⁻, the charge is balanced by adding electrons
• What happens to oxygen in the reaction O₂ + 4e⁻ → 2O²⁻?

  It gains electrons
• What is an example of an oxidizing agent in rusting?

  Oxygen (O₂)
• What is an example of a reducing agent in rusting?

  Iron (Fe)
• In the half-equation method, oxygen is balanced by adding H₂O.


  True
• In a redox reaction, electron transfer leads to changes in oxidation states.


  True
• What is one benefit of using redox reactions in metal extraction?

  Efficient extraction
• In the extraction of iron, Fe₂O₃ is reduced to Fe by gaining electrons from CO.


  True