full helpful papers (electrolysis)

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REDOX



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



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?



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 "#"$%#.



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%#)(%#.



!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,



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.



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#



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, '&



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?



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.



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



!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



&sing O'!R'(What does O!R" stand for in terms of redox reactions?

Oxidation

s

!oss of electrons

Reduction

s

"ain of electrons



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?



(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

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