4.3 Redox Reactions

• What happens to the oxidation number of a substance during reduction?

  Decreases
• To balance a redox equation, you must first identify the oxidation and reduction half-reactions
• In reduction, the oxidation number of an element decreases.


  True
• Which substance donates electrons in the reaction between iron and copper sulfate?

  Iron
• Copper ions in copper sulfate are reduced to copper metal when they accept electrons from iron.


  True
• The oxidizing agent in a redox reaction oxidizes other substances by accepting their electrons
• Which type of agent is oxidized in a redox reaction?

  Reducing agent
• In a redox reaction, the oxidizing agent is reduced, meaning it gains electrons.
• When balancing half-reactions, hydrogen atoms are balanced by adding H⁺ ions.


  True
• Reduction is defined as the gain of electrons by a substance.
• What is the role of the reducing agent in electron transfer?

  Donates electrons
• In the reaction Fe (s) + CuSO₄ (aq) → FeSO₄ (aq) + Cu (s), what does copper sulfate (CuSO₄) act as?

  Oxidizing agent
• In a redox reaction, what happens to the oxidizing agent?

  It is reduced
• Oxygen atoms are balanced in redox reactions by adding H₂O molecules.


  True
• What is reduction in a redox reaction?

  Gain of electrons
• In a redox reaction, the oxidizing agent gains electrons.


  True
• To balance charges in a half-reaction, electrons must be added
• What is the balanced redox reaction for Fe²⁺ + Cr₂O₇²⁻ → Fe³⁺ + Cr³⁺?

  6Fe²⁺ + Cr₂O₇²⁻ + 14H⁺ → 6Fe³⁺ + 2Cr³⁺ + 7H₂O
• Iron extraction in a blast furnace uses coke as a reducing agent.


  True
• What is the definition of oxidation in a redox reaction?

  Loss of electrons
• Oxidation and reduction always occur together
• Match the terms with their definitions:

  Electron Transfer ↔️ Movement of electrons between reactants

  Oxidizing Agent ↔️ Accepts electrons

  Reducing Agent ↔️ Donates electrons
• An oxidizing agent causes oxidation by accepting electrons
• What does a reducing agent do in a redox reaction?

  Donates electrons
• Match the properties with their agents:

  Oxidizing Agent ↔️ Accepts electrons and causes reduction

  Reducing Agent ↔️ Donates electrons and causes oxidation
• Identifying oxidizing and reducing agents is crucial for understanding electron transfer in redox reactions.


  True
• What is the definition of an oxidizing agent in redox reactions?

  Accepts electrons
• Steps for balancing redox equations using the half-reaction method

  1️⃣ Identify the elements oxidized and reduced

  2️⃣ Write the separate half-reactions for oxidation and reduction

  3️⃣ Balance the half-reactions

  4️⃣ Multiply half-reactions to equalize electron transfer

  5️⃣ Add the balanced half-reactions
• What happens to the oxidation number of an element during oxidation?

  Increases
• Oxidation and reduction always occur together in redox reactions.


  True
• In the reaction Fe (s) + CuSO₄ (aq) → FeSO₄ (aq) + Cu (s), iron (Fe) is the reducing agent.
• The reducing agent donates electrons and causes oxidation.


  True
• Balancing redox equations ensures the number of atoms and charges are equal on both sides.
• What is oxidation in a redox reaction?

  Loss of electrons
• The reducing agent is oxidized when it loses electrons
• Steps for balancing redox equations using the half-reaction method

  1️⃣ Separate the reaction into oxidation and reduction half-reactions

  2️⃣ Balance each half-reaction for atoms other than oxygen and hydrogen

  3️⃣ Balance oxygen by adding H₂O molecules

  4️⃣ Balance hydrogen by adding H⁺ ions

  5️⃣ Balance charges by adding electrons

  6️⃣ Multiply half-reactions to equalize electron transfer

  7️⃣ Add the balanced half-reactions and simplify common terms
• Adding balanced half-reactions involves canceling common terms on both sides.


  True
• In metal extraction, the first stage involves the oxidation of the metal in its ore
• Match the component with its redox process in iron extraction:

  Iron Ore ↔️ Oxidation

  Coke ↔️ Reducing Agent

  Limestone ↔️ Flux
• What is the role of an oxidizing agent in a redox reaction?

  Accepts electrons