3.2.5.4 Redox Reactions

• What is a redox reaction defined as?

  Change in oxidation number
• In the reaction `Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂(aq) + 2Ag(s)`, copper is oxidized
• What is the definition of oxidation in redox reactions?

  Loss of electrons
• Where are electrons added to balance the charge in a reducing half-equation?

  Left side
• What does a reducing half-equation show in terms of electron transfer?

  Gain of electrons
• The half-equation Fe²⁺(aq) → Fe³⁺(aq) represents oxidation.


  True
• In basic conditions, OH⁻ ions are added to neutralize excess H⁺
• Match the half-equation type with its characteristic:

  Oxidizing Half-Equation ↔️ Electrons appear on the right side

  Reducing Half-Equation ↔️ Electrons appear on the left side
• Where are electrons located in a reducing half-equation?

  Left side
• Redox reactions involve the transfer of electrons.


  True
• Oxidation involves the loss of electrons and an increase in oxidation number.


  True
• What happens to the oxidation number of silver ions (Ag⁺) during the reaction?

  Decreases from +1 to 0
• Reduction involves the gain of electrons and a decrease in oxidation number
• Multiplying half-equations by appropriate factors ensures the number of electrons is equal.


  True
• In an oxidizing half-equation, a species loses electrons.

  True
• What is added to the left side of the reduction half-equation in acidic conditions to balance oxygen atoms?

  H₂O
• What happens to the oxidation number during reduction?

  It decreases
• When balancing atoms in a half-equation, oxygen and hydrogen are balanced last.


  True
• Oxidation is defined as an increase in oxidation number.
• Match the concept with its definition:

  Oxidation ↔️ Increase in oxidation number, loss of electrons

  Reduction ↔️ Decrease in oxidation number, gain of electrons
• What happens to the oxidation number during oxidation?

  It increases
• When balancing atoms in half-equations, oxygen and hydrogen are balanced last.

  True
• Steps in the half-equation method for balancing redox equations

  1️⃣ Write the unbalanced redox equation

  2️⃣ Separate into half-equations

  3️⃣ Balance the atoms except oxygen and hydrogen

  4️⃣ Balance oxygen and hydrogen

  5️⃣ Balance the charge

  6️⃣ Equate the number of electrons

  7️⃣ Combine and simplify
• Why is it necessary to equate the number of electrons in half-equations?

  To combine the equations
• Hydrogen is balanced by adding H⁺ to the opposite side where H₂O was added.


  True
• Steps to balance the reduction half-equation in the example reaction `MnO₄⁻(aq) → Mn²⁺(aq)`

  1️⃣ Balance Mn atoms

  2️⃣ Balance oxygen by adding H₂O

  3️⃣ Balance hydrogen by adding H⁺

  4️⃣ Balance the charge with electrons
• In acidic solutions, hydrogen is balanced by adding H⁺ ions.


  True
• The oxidation half-equation for iron(II) to iron(III) is Fe²⁺
• How many hydrogen ions are added to balance hydrogen in the reduction half-equation for permanganate?

  8
• What method is used to balance complex redox equations by separating them into oxidation and reduction half-equations?

  Half-equation method
• Hydrogen ions (H⁺) are added to balance hydrogen in acidic conditions.

  True
• Transition metal ions can act as either oxidizing or reducing agents due to their variable oxidation states.


  True
• What is the half-equation for the oxidation of a metal ion M²⁺ to M³⁺?

  M^{2+}(aq) \rightarrow M^{3+}(aq) + e^{-}</latex>
• In the reaction Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂(aq) + 2Ag(s), which substance is oxidized?

  Copper
• In a redox reaction, reduction involves the gain of electrons
• Combining the half-equations involves canceling out common species
• The half-equation method is a systematic way to balance complex redox equations.

  True
• What is the unbalanced redox equation in the example given?

  MnO₄⁻(aq) + Fe²⁺(aq) → Mn²⁺(aq) + Fe³⁺(aq)
• Match the half-equation type with its definition:

  Oxidizing Half-Equation ↔️ Shows the loss of electrons

  Reducing Half-Equation ↔️ Shows the gain of electrons
• In the reaction between Fe²⁺ and MnO₄⁻, Fe²⁺ acts as the reducing agent.


  True