For this example we will predict the
products, balance the chemical equation,
then using a solubility table we'll
identify the solubility of each compound,
then we'll find the complete ionic
equation and finally we'll find the net
ionic equation.
Alright, let's predict our products. So
we're given our reactants here and the
concept of the inner with the inner and
outer with the outer, what I mean by that
is the inner elements will combine to
form our product and then so will the
outer elements will combine to form our
other product. So with the inner with the
inner, we'll start off with lead and
chlorine. You always want to put the
positive charge, which is the metal and
then the negative charge which is the
nonmetal, together. So always put the
metal first then the nonmetal. And then
we know that lead is a 2+ charge
and chlorine is a -1
charge. So what will happen is this two
is going to come down and go with our
chlorine because it has to be our
subscript. so our first compound or our
first product will be lead chloride. Next
we're gonna do the outer with the outer
and we'll see that potassium and nitrate
will combine. So you'll note that
potassium has a +1 charge, nitrate
has a -1 charge and then our
charges are completely balanced. So then
our next product would be potassium
nitrate. Let's balance this equation. When
we're balancing chemical equations I
always like to put the elements on
opposite sides, so I'll make one list of
elements on the reactants and one list
of elements on the products. Now whenever
you have like nitrate in this case or
any sort of polyatomic ion, I like to
keep those intact because, we only do
this by the way if we have them the same
on either side. So I'm going to leave
NO3 together because
it makes it so much easier to balance.
Now let's see how much of each element
we have, so for potassium there's only
one chlorine. There's one lead. There's
one and then nitrate there's actually
two and that's due to this little 2
subscript there. So I know there's
actually 2 nitrates. Next moving on to
our products there's only one potassium
and now there are two chlorines and then
next there's one lead and one nitrate.
Okay so it doesn't matter the order as
to which element you want to start
balancing first. I'm going to start off
with chlorine, so since on our product
side there are two chlorine and then on
our reactant there's only one, I'm going
to place a 2 in front of that entire
compound of KCl and then what will
happen it's like you're distributing and
now we have two potassium and two
chlorines but everything else remain the
same. So what's left to balance is that
nitrate. Now I'll put a 2 in front of
potassium nitrate and once again this is
going to distribute. So we'll have two
potassium and two nitrates and then
everything else stays the same. Now we're
completely balanced. Now let's move on to
identifying our solubility of every
single compound. So whenever we're
looking at solubility, we're gonna have
to look at a solubility table. Now what I
like to do when I'm predicting a
solubility of, let's say any sort of
compound, in this specific case of
chlorine of KCl. I like to look at
chlorine first. And I'm gonna see where
is chlorine on my solubility table. Well
that's a halogen and those are typically
soluble with the exception of these
three metals.
Now since potassium is in Group one
that's always going to be soluble so I
know that this compound must be soluble
making it aqueous and then I'll keep going.
So now to our next reactant, I'll look at
the last portion of the compound so that
nitrate. And then nitrate is right here
in our solubility table, it's always
going to be soluble because there are
no exceptions to our rule. So we know
this again would be aqueous. Moving on
we'll see that same sort of case here where we have NO3 and that's
nitrate again. Nitrate has no
exceptions so it's going to be soluble
which means it's aqueous. And then lastly
we'll see we have chlorine again but you
note that lead is one of those
exceptions, so since it is an exception
to that rule that means this must be a
solid. Now that we've identified all of
the solubilities for every single one of
these compounds, let's write our complete
ionic equation which is also known
as our total ionic equation. So whenever
we're looking at a complete ionic
equation, what we're going to do is for
all the compounds that are aqueous and
only the ones that are aqueous, you will
break apart those compounds into their
separate ions. Remember an ion is just an
element with a charge. So anytime we'll
see a solid like in this case you're not
going to do anything to that solid but
leave it alone and leave it intact. So
let's start breaking everything apart.
So our first aqueous compound is KCl and
I'm going to break this apart into its
separate ions. And we'll see there is
actually two potassium and two chlorines
because I want you to think of this as
this two is really distributing into
both. So that's why we have two potassium
and potassium has a plus one charge. we'll
also state that it's aqueous. Next we'll
see that there are two chlorines.
Chlorine has a negative one charge
that's also aqueous. And we'll move on to
our second reactant, so this compound is
still aqueous, that's why we're able to
break it apart into its ions. And we'll
see, okay we have lead that has a two
plus charge and that's also aqueous, but
we'll note that there are two nitrates
here because
of this 2 subscript that we had
initially. So that's why we have 2 NO3's
with that negative one charge
and it's also aqueous. And lastly this is
our last compound that's aqueous that
we'll break apart. So we'll have two
potassium with the positive charge and
it's aqueous and two nitrates with its
negative charge and it's also a aqueous.
Now with this solid we're going to leave
it alone, don't break that apart. So we
never break any solids or liquids and
then for aqueous, aqueous is the only one
that you're going to break apart. Now
let's write our complete ionic equation
by adding all of your reactants together
and adding all of your products together.
So we'll see that our complete ionic
equation would be this big ole long
thing. And what we're gonna do next to
finally get our net ionic equation is,
you're gonna cancel out any like terms
or any like ions,
so these are known as spectator ions. A
spectator ion means we will see that on
the reactant and on the product side.
So our spectator ions in this case would
be potassium, because we have potassium
on our reactants and our product side so
those cancel plus our other spectator
ion would be our nitrate since those
also cancel out. Now let's look at this
okay, so for your net ionic equation
you're always going to have the ions as
your reactants that are needed to form
your solid. So we needed chlorine, two
chlorines to be exact, and we needed lead
to form our final products or that final
solid. So those two must be added
together to give you your net ionic
equation and that would be our final
answer. All right so this was a packed
example I know, if you guys need more
help with solubility and understanding
how to read a solubility table, make sure
to check out my latest video and make
sure to download your
solubility table, the link is in the
description box. Now I know that there's
a lot to all of these concepts and at
times you may feel like giving up but a
lot of times when you feel that way you
are closer to succeeding then you really
think, trust me I've been through it. So
keep moving forward guys and I'll see
you in the next video.
