Oxidation, Reduction and Redox Equations-NOTES

• What is oxidation defined as?

  Loss of electrons
• What is reduction defined as?

  Gain of electrons
• What are redox reactions?

  • Reactions where oxidation and reduction occur simultaneously
  • One species loses electrons while another gains them
  • Known as reduction-oxidation reactions
• What acronym helps remember the redox rule?

  OILRIG
• What does oxidation number indicate?

  The oxidation state of an element or ionic substance
• What are the rules for determining oxidation states?

  • Oxidation state of an element is zero
  • Oxidation states in a neutral compound add up to zero
  • Oxidation states in a charged compound add up to total the charge
  • Hydrogen has an oxidation state of +1
  • Oxygen has an oxidation state of -2
  • All halogens have an oxidation state of -1
  • Group I metals have an oxidation state of +1
• How do you find the oxidation number of sulfur in a compound that totals zero?

  By solving the equation: \(2 - 8 + x = 0\)
• What does an oxidising agent do?

  Accepts electrons from the species being oxidised
• What happens to the oxidation number of an oxidising agent?

  It decreases (gets more negative)
• What does a reducing agent do?

  Donates electrons to the species being reduced
• What happens to the oxidation number of a reducing agent?

  It increases (gets more positive)
• What are half equations used for?

  • To show separate oxidation and reduction reactions in a redox reaction
  • Must be balanced in terms of species and charges

  
• What is the method for balancing half equations?

  1. Balance all species excluding oxygen and hydrogen
  2. Balance oxygen using \(H_2O\)
  3. Balance hydrogen using \(H^+\) ions
  4. Balance changes using \(e^-\) (electrons)

  
• How can half equations be combined?

  • To determine the overall redox reaction
  • Ensure the number of electrons is the same for both half equations
  • Scale up the number of moles if necessary