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Oxidation and Reduction

Edexcel AS-level ChemistryTopic 5 of 2114 lessons

Revision notes for Oxidation and Reduction in Edexcel Chemistry (8CH0). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.

  1. Oxidation and ReductionOxidation can be defined as: • gain of oxygen • loss of hydrogen • loss of electrons • increase in oxidation number.
  2. Oxidising and Reducing AgentsAn oxidising agent is a substance that causes oxidation by accepting electrons thereby decreasing its oxidation state.
  3. DisproportionationDisproportionation is the simultaneous oxidation and reduction of an element in a single reaction.
  4. Oxidation NumberThe oxidation number of an atom is the number of electrons it gains or loses in forming a compound. • the oxidation number of uncombined elements is…
  5. Systematic NamesThe names of compounds include the oxidation state of the element that can have variable oxidation states in Roman numerals.
  6. Example Question 1Question: Work out the oxidation number of (a) manganese in MnO4−, (b) chromium in Cr2O72− and (c) sulfur in S2O32−.
  7. Example Question 2Question: Iron(III) ions react with iodide ions in aqueous solution: 2 Fe3+ (aq) + 2 I− (aq) → 2 Fe2+ (aq) + I2 (aq) (a) Use oxidation numbers to…
  8. Ionic EquationsAny redox reaction is made up of two half-reactions: in one of them electrons are being lost (an oxidation process) and in the other one those…
  9. Exam-style Question 1Question (3 marks): In acidic solution, manganate(VII) ions oxidise iron(II) ions to iron(III) ions.
  10. Exam-style Question 2Question (4 marks): When copper(I) oxide is added to warm dilute sulfuric acid, a pink-brown solid and a blue solution form: Cu2O (s) + H2SO4 (aq) →…
  11. Exam-style Question 3Question (3 marks): In acidic solution, dichromate(VI) ions are reduced to chromium(III) ions.
  12. Exam-style Question 4Question (3 marks): Copper reacts with concentrated nitric acid to give copper(II) nitrate, nitrogen dioxide and water.
  13. Exam-style Question 5Question (4 marks): Hydrogen peroxide oxidises iodide ions in acidic solution: H2O2 (aq) + 2 H+ (aq) + 2 I− (aq) → I2 (aq) + 2 H2O (l) (a) Give the…
  14. Exam-style Question 6Question (4 marks): Sulfur dioxide decolourises bromine water: SO2 (aq) + Br2 (aq) + 2 H2O (l) → SO42− (aq) + 4 H+ (aq) + 2 Br− (aq) (a) Use…

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