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REDOX
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STARTER: W hat happens when we burnM agnesium in air?
Try include the following
ideas in your answer!
Activation energy
Balanced equation
Movement of molecules
Rate of reaction
Gain of oxygen
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Oxidation is the addition of oxygen to a substance and
reduction is the removal of oxygen from a substance.
leadoxide
+ carbon lead carbonmonoxide
+
oxygen removed
reduction
oxygen added
oxidation
Reduction and oxidation always take place together.
Why is this type of reaction called a redox reaction?
redox = reduction and oxidation
Which substances are oxidized and reduced in this reaction?
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Oxidation is gain of oxygen
When magnesium reacts with oxygen inthe air:
2Mg + 2 2Mg
It is easy to see that the magnesium has
gained oxygen and an oxidation reaction has occurred.
The magnesium has been "#"$%#.
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Reduction is oss of oxygen
When lead is extracted from lead (II) oxide, car&on is used to remove the oxygen
2'& + ( 2'& + (2
The oxygen has been removed from the
lead (II) oxide
The lead (II) oxide has been R%#)(%#.
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!ets oo" at this further#
What actually happens when themagnesium joins with oxygen
The magnesium atom *$%$%*%(TR$ to become a magnesium ion
We can write what happens li!e this:
Mg Mg2+ + 2e,
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Oxidation and eectron ossWhen magnesium burns in oxygen to form magnesium oxide,
what happens to magnesium and its electrons?
Oxidation is the loss of electrons.
oxidized
(electrons lost)
Mg Mg2+ O2-O+
The magnesium has been oxidized. The Mg atom has lost 2 electrons to form a Mg2+ ion.
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Oxidation is oss of eectrons
"o, when magnesium ta!es part in anoxidation reaction it loses electrons.
When magnesium reacts with chlorineit also loses electrons.
Mg + (l2Mg(l2
This is an oxidation reaction too#
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Reduction is gain of eectrons
In the compound lead (II) oxide thelead is an ion, $b%&
In order to form lead the $b%& ion has toGA" % electrons
We can write this as follows:
'&2+ + 2e, '&
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Redox and eectronsMagnesium burns in oxygen
to form magnesium oxide.
redox reaction can also
be explained in terms of the
gain or loss of electrons.
magnesium + oxygen magnesium oxide
2Mg (s) O2 (g) 2MgO (s)+
What happens to the atoms and electrons in this reaction?
!t is ob"ious that the
magnesium has been
oxidized, but what has
happened to the oxygen?
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Reduction and eectron gainWhen magnesium burns in oxygen to form magnesium oxide,
what happens to oxygen and its electrons?
Reduction is the gain of electrons.
reduced
(electrons gained)
Mg Mg2+ O2-O+
The oxygen has been reduced. The # atom has gained 2 electrons to form a O2-
ion.
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Redox
'ou may hae noticed that when themagnesium loses its electrons they are gained by the oxygen
xidation (loss of electrons) andreduction (gain of electrons)happen simultaneously.
We call these R%# reactions
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!et$s act it out%
ae a loo! at the elements*ions
Which need to lose electrons to gain+oble gas conguration
Which gain electrons to get to +oblegas conguration
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&sing O'!R'(What does O!R" stand for in terms of redox reactions?
Oxidation
s
!oss of electrons
Reduction
s
"ain of electrons
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W hat is a haf)e*uation?$edox reactions in"ol"e the transfer of electrons.
oxidation# Mg Mg2+ + 2e-
magnesium + oxygen magnesium oxide
2Mg (s) O2 (g) 2MgO (s)+
reduction# O2 + $e- 2O2-
%&uations written to show what happens to the electronsduring oxidation and reduction are called %alf-e&uations.
What are the half'e&uations for the oxidation and reduction
processes in this reaction?
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(RO&+ +RO,!EM :
In the reactions below, which element isbeing oxidised and which reduced
-. %a & /% %a/
%. +a0r & l% +al & 0r%
1. %2l & 3e%/1 %3e & 2l%/1
.an you write half e4uations for thereactions ta!ing place