Redox o h

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Redox o h

  1. 1. Redox Reactions What is the meaning of REDOX? R E D O X Ox idation Red uction
  2. 2. Examples of Redox Reactions which occur in daily life <ul><li>Combustion </li></ul><ul><li>Corrosion/Rusting </li></ul><ul><li>Photosynthesis </li></ul><ul><li>Respiration </li></ul>
  3. 4. Defn 1 (In terms of oxygen) Oxidation = addition/gain of oxygen A substance that gains oxygen is said to be oxidised. Reduction = removal/loss of oxygen. A substance that loses oxygen is said to be reduced.
  4. 5. Example based on Defn 1 (In terms of oxygen) <ul><li>Zn + PbO -> ZnO + Pb </li></ul><ul><li>Zinc (Zn) is oxidised because it gains oxygen to form zinc oxide . </li></ul><ul><li>Lead (II) oxide (PbO) is reduced because it loses oxygen to form lead . </li></ul><ul><li> </li></ul>When one substance is oxidised, another substance must be reduced. Oxidation and reduction take place at the same time. Such reactions are called REDOX reactions.
  5. 6. Example based on Defn 1 (In terms of oxygen) 2. Fe 2 O 3 + 3CO -> 2Fe + 3CO 2 Carbon monoxide (CO) is oxidised. Iron (III) oxide (Fe 2 O 3 ) is reduced.
  6. 7. Defn 2 (In terms of hydrogen) Oxidation = removal/loss of hydrogen A substance that loses hydrogen is said to be oxidised. Reduction = addition/gain of hydrogen. A substance that gains hydrogen is said to be reduced.
  7. 8. <ul><li>H 2 S + Cl 2 -> 2HCl + S </li></ul><ul><li>The substance oxidised is </li></ul><ul><li>h ydrogen sulfide (H 2 S) because it loses hydrogen to form sulfur . </li></ul><ul><li>The substance reduced is </li></ul><ul><li>c hlorine (Cl 2 ) because it gains hydrogen to form hydrogen chloride . </li></ul><ul><li>2. CH 4 + Cl 2 -> CH 3 Cl + HCl </li></ul><ul><li>Substance oxidised is methane (CH 4 ). </li></ul><ul><li>Substance reduced is chlorine (Cl 2 ). </li></ul><ul><li> </li></ul>Example based on Defn 2 (In terms of hydrogen)

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