Redox Reactions: Electron Transfer Fundamentals

Year 13 Chemistry Understanding Oxidation and Reduction Taupo-nui-a-Tia College

Learning Intentions

Explain oxidation-reduction in terms of electron transfer Understand oxidation states and numbers Identify oxidising and reducing agents Write and balance redox equations

What happens when iron rusts?

Think about the chemical changes What role does oxygen play? Is this a simple reaction?

What are Redox Reactions?

REDuction + OXidation = REDOX Involve the transfer of electrons One species loses electrons (oxidation) Another species gains electrons (reduction) Always occur together

Oxidation Number Rules

Practice: Assigning Oxidation Numbers

Work in pairs Assign oxidation numbers to: H₂SO₄ CuSO₄ CO₃²⁻ Check your answers with the rules

Defining Oxidation and Reduction

OXIDATION = Loss of electrons OXIDATION = Increase in oxidation number REDUCTION = Gain of electrons REDUCTION = Decrease in oxidation number Remember: OIL RIG (Oxidation Is Loss, Reduction Is Gain)

Oxidation vs Reduction Comparison

{"left":"Loss of electrons\nIncrease in oxidation number\nSubstance is oxidized\nActs as reducing agent","right":"Gain of electrons\nDecrease in oxidation number\nSubstance is reduced\nActs as oxidizing agent"}

Oxidizing and Reducing Agents

Oxidizing agent (oxidant): - Causes oxidation in other substances - Gets reduced itself - Gains electrons Reducing agent (reductant): - Causes reduction in other substances - Gets oxidized itself - Loses electrons

Example: Magnesium Burning in Air

2Mg + O₂ → 2MgO Identify what is oxidized Identify what is reduced Name the oxidizing and reducing agents Show oxidation number changes

Writing Half-Equations

Separate oxidation and reduction processes Show electron transfer explicitly Balance atoms and charge Oxidation half-equation: Mg → Mg²⁺ + 2e⁻ Reduction half-equation: O₂ + 4e⁻ → 2O²⁻

Practice: Iron and Copper Sulfate

Fe + CuSO₄ → FeSO₄ + Cu Write the half-equations Identify oxidation numbers Balance the electrons Combine to form the full equation