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Redox Reactions (Oxford AQA IGCSE Chemistry): Revision Note

Exam code: 9202

Philippa Platt

Written by: Philippa Platt

Reviewed by: Stewart Hird

Updated on

Redox Reactions

  • When oxidation and reduction are happening at the same time this is known as a redox reaction

  • For example

zinc + copper sulphate → zinc sulphate + copper

Zn + CuSO4 → ZnSO4 + Cu

  • The ions present (with state symbols) in the equation are:

Zn (s) + Cu2+ (aq) + SO42- (aq) →Zn2+ (aq) + SO42- (aq) + Cu (s)

  • The spectator ions (those that do not change) are SO42-(aq) and are removed

Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)

  • We can split the reaction into two half equations

Zn (s) → Zn2+ (aq) + 2e-

Cu2+ (aq) + 2e- → Cu (s)

  • Zinc has been oxidised as it has lost electrons 

  • Copper ions have been reduced as they have gained electrons

Worked Example

When iron reacts with bromine to form iron(II) bromide, a redox reaction reaction occurs:

Fe + Br2 →  FeBr2

What has been reduced in the reaction?

Answer:

Step 1 - Write half equations to work out what has gained/lost electrons

Fe → Fe2+ + 2e-

Br2 + 2e- → 2Br-

Fe loses electrons; Br2 gains electrons

Step 2 - Deduce what has been oxidised/reduced (remember OIL RIG)

Fe has been oxidised as it has lost electrons

Br2 has been reduced as it has gained electrons

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    Author
    Reviewer
    Philippa Platt

    Author: Philippa Platt

    Expertise: Chemistry Content Creator

    Philippa has worked as a GCSE and A level chemistry teacher and tutor for over thirteen years. She studied chemistry and sport science at Loughborough University graduating in 2007 having also completed her PGCE in science. Throughout her time as a teacher she was incharge of a boarding house for five years and coached many teams in a variety of sports. When not producing resources with the chemistry team, Philippa enjoys being active outside with her young family and is a very keen gardener

    Stewart Hird

    Reviewer: Stewart Hird

    Expertise: Chemistry Content Creator

    Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.