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Redox Reactions

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Redox Reactions Chemical Reactions ... a similar equation for the reaction of zinc and iron oxide. ... atoms Potassium atoms turning into potassium ions Nickel atoms ... – PowerPoint PPT presentation

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Title: Redox Reactions


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

3
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
CaO Ca O2
2
2
5
Redox reactions
Whenever a chemical is oxidised, another chemical
must be reduced, and vise vera EXAMPLE
Mg CuO MgO Cu
  • Write a similar equation for the reaction of zinc
    and iron oxide.
  • Label the oxidation and reaction steps

6
Introducing electrons
  • Mg CuO MgO Cu
  • The oxidation and reduction steps can be written
    out separately
  • Mg MgO
  • CuO Cu

Mg2O2-
OXIDATION
REDUCTION
Cu2O2-
Re-write the above two steps, but add charges to
the ions involved
7
  • In the oxidation step
  • Mg O2 Mg2O2-
  • 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
  • They have been taken by the copper
  • Cu2O2- 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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