Chemistry Redox Reactions Quiz

Oxidation & Reduction

• Oxidation Reaction: A chemical reaction involving the addition of oxygen to a substance, the removal of hydrogen from a substance, or the loss of electrons from an atom.
• Reduction Reaction: A chemical reaction involving the removal of oxygen from a substance, the addition of hydrogen to a substance, or the gain of electrons by an atom.
• Redox Reaction: A reaction where oxidation and reduction occur simultaneously, involving the transfer of electrons between substances. Reactions involving the loss or gain of electrons are considered redox reactions.

Example of Oxidation

• 2Cu + O₂ → 2CuO: Addition of oxygen to copper.
• H₂S + Cl₂ → 2HCl + S: Removal of hydrogen from H₂S and addition of hydrogen to chlorine. Loss of electrons from H₂S and gain of electrons from chlorine.
• 2FeCl₂ + Cl₂ → 2FeCl₃: Gain of electrons by chlorine; transfer of electrons from Fe²⁺ to Cl₂.

Example of Reduction

• CuO + H₂ → Cu + H₂O: Removal of oxygen from CuO to form Cu and addition of hydrogen to CuO to form H₂O.
• Cl₂ + H₂S → 2HCl + S: Addition of hydrogen to chlorine, gain of electrons to form HCl; oxidation of hydrogen sulfide to form sulfur with loss of electrons.
• 2FeCl₃ + SO₂ + 2H₂O → 2FeCl₂ + 2HCl + H₂SO₄: Gain of electrons to become Fe²⁺ .

Oxidizing Agents

• Substances that lose oxygen or gain hydrogen or accept electrons.
• Examples include O₂, Cl₂, H₂O₂, conc. H₂SO₄, conc. HNO₃, MnO₂, PbO₂, Pb₃O₄, KNO₃.

Reducing Agents

• Substances that gain oxygen or lose hydrogen or donate electrons.
• Examples include H₂, CO, SO₂, H₂S, NH₃, HCl, metals (e.g., K, Na).
• The substance that gets reduced acts as an oxidizing agent, while the substance that gets oxidized acts as a reducing agent.