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Red ox Reactions

Red ox Reactions. Chemical Reactions. There are 3 major classes of chemical reaction: 1. Precipitation 2. Acid-base 3. Redox. Fe + O 2 FeO. Oxidation. Refers to the gain of oxygen in a chemical reaction EXAMPLE: Iron + oxygen. Iron(II) oxide.

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Red ox Reactions

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  1. Redox Reactions

  2. Chemical Reactions • There are 3 major classes of chemical reaction: 1. Precipitation 2. Acid-base 3. Redox

  3. Fe + O2 FeO Oxidation • Refers to the gain of oxygen in a chemical reaction • EXAMPLE: Iron + oxygen Iron(II) oxide Write the chemical equation (unbalanced) The iron has gained oxygen and has been oxidised

  4. Reduction • Is the opposite of oxidation • This means that it involves the lose of oxygen Write a chemical equation for the reduction of calcium oxide. Balance the equation 2 CaO Ca + O2 2

  5. Redox reactions Whenever a chemical is oxidised, another chemical must be reduced, and vise vera EXAMPLE: Mg + CuOMgO + Cu Write a similar equation for the reaction of zinc and iron oxide. Label the oxidation and reaction steps

  6. Introducing electrons Mg + CuOMgO + Cu The oxidation and reduction steps can be written out separately: Mg MgO CuO Cu Mg2+O2- OXIDATION REDUCTION Cu2+O2- Re-write the above two steps, but add charges to the ions involved

  7. In the oxidation step: Mg + O2 Mg2+O2- The magnesium atoms have turned into magnesium ions Have they gained or lost electrons? OXIDATION IS ALWAYS LOSS of electrons O.I.L. Where have the electrons gone to?

  8. 2+ 2- NEUTRAL + Cu2+ Cu 2e + They have been taken by the copper: Cu2+O2- Cu The copper has turned from ions into atoms REDUCTION IS ALWAYS GAIN of electrons R.I.G.

  9. Practice • Write similar ion-electron equations for: Calcium ions turning into calcium atoms Sodium ions turning into sodium atoms Aluminium ions turning into aluminium atoms Potassium atoms turning into potassium ions Nickel atoms turning into nickel(II) ions All of these REDUCTIONS can be found in the data booklet

  10. Writing ion-electron equations • All reductions are found in data booklet • To write the oxidation, reverse the equation Cu2+ + 2e Cu Cu Cu2+ + 2e • Both sides of the equation should be neutral when the charges are added together • REMEMBER: OIL RIG

  11. Problems • Look at the following equation: Zn + Ag2O ZnO + Ag • Which chemical is being oxidised? • Write an ion-electron equation for the oxidation step. • Write an ion-electron equation for the reduction step. 2. Assessment tests 10.3 and 10.4

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