Redox

• What are redox reactions?

  Electron transfer reactions involving oxidation and reduction
• What occurs simultaneously in redox reactions?

  Oxidation and reduction
• How do you determine oxidation states from a balanced equation?

  Write oxidation states above known elements
• What is the first step in balancing redox equations?

  Write half equations for the reaction
• What is the process to balance charges in redox equations?

  Add electrons to balance charges
• What is the final step in balancing redox equations?

  Cancel out the electrons on both sides
• What is the focus of this AQA revision video?

  Oxidation reduction and Redux reactions
• What acronym helps to remember oxidation and reduction?

  Oil rig
• What does oxidation refer to in terms of electrons?

  Loss of electrons
• What does reduction refer to in terms of electrons?

  Gain of electrons
• How do you determine which element is oxidised or reduced in a balanced equation?

  By comparing oxidation numbers
• What is a reducing agent?

  A substance that loses electrons
• What is an oxidizing agent?

  A substance that gains electrons
• What is the oxidation number of uncombined elements?

  Always zero
• What should you do if atoms don’t balance in half equations?

  Add H⁺ ions or H₂O molecules
• What is the oxidation number of H ions?

  Same as the charge on the ion
• What are the steps to derive half equations from a balanced equation?

  1. Put oxidation numbers above every element
  2. Identify increase in oxidation number (oxidised)
  3. Identify decrease in oxidation number (reduced)
  4. Write equations for oxidised and reduced elements
  5. Add electrons to balance
• What are the differences between reducing agents and oxidizing agents?

  • Reducing agents: lose electrons, oxidized themselves
  • Oxidizing agents: gain electrons, reduced themselves
• What is the significance of oxidation states in chemical reactions?

  • Helps determine electron transfer
  • Essential for balancing redox reactions
  • Indicates oxidation and reduction processes
• Why do we use Roman numerals in naming compounds like iron(III) oxide?

  To indicate the oxidation state of the ion
• What does oxidation refer to in terms of oxidation number?

  Increase in oxidation number
• What does reduction refer to in terms of oxidation number?

  Decrease in oxidation number
• What is a reducing agent?

  A substance that donates electrons
• What is an oxidizing agent?

  A substance that accepts electrons
• What are the steps to balance half equations?

  1. Write species before and after reaction
  2. Balance atoms except oxygen and hydrogen
  3. Balance oxygen with H2O
  4. Balance hydrogen with H+ ions
  5. Balance charges with electrons
• How do you balance the oxygen in the half equation MnO_4^{-} \rightarrow Mn^{2+}\?


  Add four $H_2O$ to the right side
• How do you balance the hydrogen in the half equation after adding water?

  Add eight $H^+$ to the left side
• What is the total charge on the left side after balancing the half equation $MnO_4^{-} +$$8H^+$$+$$5e^- \rightarrow Mn^{2+} +$ 4H_2O\?


  +7
• What is the total charge on the right side after balancing the half equation $MnO_4^{-} +$$8H^+$$+$$5e^- \rightarrow Mn^{2+} +$ 4H_2O\?


  +2
• What is the significance of balancing half equations?

  • Ensures conservation of mass
  • Maintains charge balance
  • Essential for accurate chemical equations
• What is the overall process when combining half equations?

  It shows both reduction and oxidation
• What are the key points to remember about oxidation and reduction?

  • Oxidation: increase in oxidation state
  • Reduction: decrease in oxidation state
  • Agents: reducing agent donates electrons, oxidizing agent accepts electrons