today I'd like to talk to you about oxidation
reduction
reactions these reactions involve either loss
or gain in fact both loss and gain of electrons in the chemical
the oxidation reaction reduction reaction is important
it provides us with
energy for our bodies to operate on its
that's one thing it also provides us with energy for
batteries and it's the basis for electricity
and it also is
a very important reaction for us
because it is the reaction which causes
iron to rust and reaction
is illustrated here and you'll note
that in this reaction that we have, we have a
several different things that are taking place that will talk about
the most important thing to remember about an oxidation-reduction reaction is
that
both of these have to take place at essentially the same time
if you have a loss of electrons you also have to have
them being gained by another species when we look at a reaction
like zinc
plus copper chloride
giving us
zinc chloride
plus copper
there are actually two separate things occurring
in this process the first thing is that zinc
is going from an oxidation state
of zero which is its natural state to zinc +2
one of the things that we need to remember when we write these reactions
this is called a
half reaction because it illustrates half
of the process and the reactions have to be balanced
electrically in other words the charge has to be the same on both sides of
the reaction
we have a zero charge on the left hand side we have a positive
two charge on the next side that tells us that we will need to have
two negative charges to balance that and
since we know that our electrons
have a negative charge that means that
zinc 0 going to zinc +2
is losing two electrons they're on the product side here
so zinc 0 gives zinc +2
plus 2 electrons conversely
our copper
is +2 on this
the left hand side copper is going
to copper
zero and so the question would be
where will the electrons go in this reaction well think about it
you have no charge here positive two here
electrons are going to go on the more positive side
we need two electrons to be
added here in order to get the charge balance
so we add our electrons
to the reactants
this these are examples of half reactions that we can
will look at
when we look at these two processes we have oxidation
and reduction
oxidation and reduction oxidation
is the loss of electrons reduction is the gain of electrons
you can remember this easy enough by saying
LEO
goes GER
Leo the Lion loss of
electrons oxidation, gain of electrons
reduction okay oxidation-reduction
so when we look at the previous example
zinc giving zinc +2 plus 2 electrons
this zinc is losing two electrons
so that would be loss of electrons
this is oxidation
copper +2
and two electrons gives copper
zero in this instance
the copper +2 is gaining electrons
this is reduction
now
oxidation-reduction reactions can be very slow
they can occur very quickly and one of the reactions which a lot of people
don't
really think about as being an oxidation-reduction reaction
is combustion and
if you take carbon and oxygen
and react them
carbon is going from carbon
0 to carbon +4
oxygen is going from 0 to -2
when we do this reaction
we have a lot of heat and energy that are
that are given off by the reaction and but we do have been electrons being
gained and lost
we're going from carbons going from 0
to +4 meaning it's losing electrons oxygen is going from zero
to -2 meaning it's gaining electrons so the carbon side of the reaction
is oxidation the oxygen side will be
reduction there's another form
of this that is called
spontaneous combustion
spontaneous combustion can do the same sort of things that you have here
but it occurs at a much much slower rate
but it's an equally important reaction depending
where you are oxidation-reduction reactions are
important in chemistry they're important in life
as we move forward into the further
regions of this century we'll find that we're going to be using these
reactions a whole lot more in order to
obtain energy and other things thank you