My beginner's guide for balancing equations. The first thing that I want to
let you know is that there's no magic to balancing equations. There's no secret that you can
somehow pick up and all of a sudden become a guru. The reason I made this video is that
some students just seem to struggle with how do I even do that or the concept behind it.
And so if you're really have troubles, hopefully I can kind of clear some of that up. And if
you're not, this is probably not the video for you. I would just go google balancing
equations practice and you'll find some really hard ones out there that you can try your
hand at. So let's get started. The first one we're going to talk about is the combustion
of hydrogen. This is the Hindenburg explosion and after this we quit putting hydrogen gas
into blimps for obvious reasons. But essentially what happens is hydrogen combines with oxygen.
Okay, so if we look at the equation down here at the bottom, the equation as it is
H2 + O2 yields water or H2O and we're going to get a lot of energy out of there as well.
Now the first thing we need to talk about is what these numbers actually mean. So this
2 down here is a subscript and that means that it tells you how many atoms of hydrogen
are in a molecule. And so this is what the molecule of hydrogen would look like. We're
going to have two atoms of hydrogen. The thing that you need to remember is you can never
change the subscript. Subscripts have to remain the same. Because if you change it, you're
changing what that molecule actually is. And so this would be H2, this would be O2, so
we have two oxygen molecules attached together, then finally we have H2O. H2O is one oxygen
and two hydrogens on either side. And so when I look at this, a lot of people will just
try to go and answer this but maybe we need to step back a little bit and actually look
graphically at what's going on here. And so when I look at this I can see here's reactants
before the reaction and products. And so just looking at it when these are graphically shown
you can see that I have two of these red oxygen atoms on the left side and only one on the
right. And so the first thing you might want to do is kind of double that. And so let me
do that. Okay, so now visually we've got two water molecules and so I've got two reds on
the right side and two reds on the left side. You'll also notice, so that's balanced, that
the hydrogens are changed. And so I have four hydrogens on the right side but I only have
two on the left side. So now let me click it again and we've got a balanced equation.
In other words, I can never change the subscripts, I can never change what these molecules are
but when you're balancing equations what you're trying to do is add more of the molecules
so you can see that reactants and products will be balanced. Okay. Now how do we actually
write that out? So we can put in front of here what are called coefficients. And coefficients
are numbers in front of the molecule that tells you how many there are. And so there
is one oxygen and we never write the coefficient of one. And so you don't want to write one
as a coefficient. If it's a coefficient of one you just leave it blank. But let's go
over here to H2. You've got this H2, that H2 and so you have 2 H2. So that would be
on the left side. If we go onto the right side you have this molecule of water, this
molecule of water and so we have two molecules of water on the right side. And so if we step
through this, this means we have two molecules of H2, so that would be 4 hydrogens on the
left side. After you balance an equation you want to go back and look at it to make sure
it's balanced. Over here we have 2 H2s as well so we have 4 hydrogens. We have 2 oxygens
on the left side, and we have 2, this coefficient multiplies this whole thing, so we have 2
oxygens on the right side as well. And so we would call that a balanced equation. And
so hopefully just by looking at it graphically that might help a little bit. Let's go to
the next one. The next one in a chemistry lab is, you see it all the time, this is a
Bunsen burner. And these are some flames from a Bunsen burner. And so a Bunsen burner works
using a gas called methane. And methane is CH4. So if we took a look at methane, methane
looks like this right here. It's got one carbon molecule and then it's got four hydrogens
attached around the outside. And when we burn methane, what that really means is that we're
combining methane with oxygen and we're creating these two things in complete combustion. We're
creating some carbon dioxide (CO2) gas, that's one carbon, two oxygens and then we're creating
a little bit of water (H2O). The other thing we're going to produce is going to be energy.
Okay. So if you look at this just graphically on the left side and on the right side, the
first thing, at least to me that jumps out is that there is way more hydrogen on the
left side then the right side. So the first thing I could do would be to add another water
on the right side. So if I add another water on the right side, the yellow balls on the
right now match the yellow balls on the left. The carbon, there's only one on the left,
matches the one on the right. So we must be getting really close. But I've got four reds
on the right and only have two. And so I have to add that as a whole molecule, so if I made
one more molecule of oxygen, now we have a balanced equation. So how do we write that
out? So methane on the left side, I have one methane but I'm not going to right the number
one. How many molecules of oxygen do we have? We have two. So I'm going to put a 2 as a
coefficient right here. Now on the right side we only have one carbon dioxide, so I'm not
going to put a one. But there should be in your mind a 1 there. Then how much water do
we have? We have just two waters. So I'm going to put 2 right here. Now we could go through
the whole thing. So how many carbons do we have? One on the left, one on the right. How
many hydrogen do we have? Four on the left. And this 2 is multiplied by the subscript,
so we've got 4 on the right and 4 on the left. And then if we look at oxygen, we've got 4
on the left and then we've got 2 oxygen here and we have 2 oxygen there. And so when I'm
solving and trying to balance equations, I'm not really seeing these, but if that helps
you visualize it then it will help you do better at that. So let's try it. So the only
way to get better at this is to just practice. And so let's try a few and I will show you
how I would think through this in my mind. So if we look at the first one, this H2O2
which is hydrogen peroxide. It breaks down into hydrogen gas and oxygen gas. Okay. So
how would I set this up. Well on the left side we've got H2. So if I want to write it
out I could. So I've got 2 hydrogens on the left and as far as oxygens on the left I've
got 2 oxygens as well. And so on the right side how many hydrogens do I have? I have
2 on the right and I have 2 on the left as well. And so this already is a balanced equation.
And so what do you do if you find a balanced equation that's already balanced? You don't
do anything to it. In other words we'd write a 1 in front of each of those but we never
write ones so I'm going to leave that one the way it is. Let's go to the next one. On
the left side we've got sodium (Na), we've got chlorine gas (Cl2) and then we're making
table salt. And so if you want to write this out you could. We've got Na and I've got 1
of those. I've got chlorine on the left side and I've got 2 of those. So that's on the
left side. That's on the reactant side. Now let's go to the product side. How many sodium
do we have? We only have one sodium. And how many chlorine do we have on the right side?
Well, we only have 1 chlorine so that's a problem because on the product side we only
have 1 atom of chlorine and on there reactant side we actually have 2. So how could I fix
that? Well, let's try to go back. Let's say I've got too few chlorine on this side, so
let me just try and add the next step which is to add a 2 on the right side. So by adding
a 2 on the right side I've taken care of my chlorine, so on the right side now I have
2 sodium and 2 chlorine. But I've set up another problem. In other words I have 2 sodium on
the right side so now I have to balance that over here. And so I'm going to come back over
here and write a 2 over here which makes this a 2. Okay so now we've got 2, 2, 2, 2 and
that's balanced. And so the right answer for that one is to put a 2 in front of the sodium
(Na) and then a 2 in front of the sodium chloride (NaCl). And that's a balanced equation. Remember
you can never change the subscript. Alright. Let's do another one. And so these are getting
progressively harder and so I'll give you some tips as far as that goes. The first tip
would be this. If we look at this one we've got silver sulfide (Ag2S), Silver (Ag) and
Sulfur (S8). So this 8 jumps out right away. So on the right side I've got 8 sulfur atoms.
If we look on the left side I've only got 1. And so as a bare minimum I'm going to try
writing an 8 right here and let's see what that does. Well now we have 8 sulfur on the
left side, 8 sulfur on the right side, but our silvers aren't matching. So on the left
side we actually have 16 silver but on the right side we only have 1. And so let me trying
just writing a 16 down. So now that's a balanced equation. So we could go through. 16 silver,
16 silver, 8 sulfur, 8 sulfur and that's going to be a balanced equation. The nice thing
about balancing equations is you can always check it at the end and you know that you
are right. It's not like maybe you're right, you absolutely are right as long as you're
just adding the coefficients. Alright. So here's the ones that are more likely that
you're going to find. And so let's work through this and always be patient remembering that
if you get frustrated you can just erase them all. Start over again. You should be able
to figure them all out. It's just kind of a guess and check. But let me show how I would
think this one out. So I've got water (H2O), carbon dioxide (CO2), got a hydrocarbon (C7H8)
here and then we've got an oxygen (O2). And so on the right side, the thing that jumps
out to me right away is we've got 7 carbons on the right side and so what I'm going to
try to do is put a 7 over here. Okay. So what does that do for me? Now I've got my 7 carbons
taken care of. The other thing that jumps out right away is on the right side I have
8 hydrogens and water is the only thing on the left side that actually has hydrogens.
And so there's an 8 here and let me try putting a 4 over here. Okay, so what that does is
give me hydrogen on the left is going to get me 8. Hydrogen on the right side is going
to get me 8 as well. Now I love it when I solve these and I get down to just like one
thing left and it has one atom in it. And so I think carbons and hydrogens are good
on either side but let me take a look at the oxygen. On the left side we have 4 oxygens.
So in this molecule of 4 waters. And then we have 14 here. So I've got 14 total oxygen,
14 here and 4 then over here, and so how do I get to, so again I've got 18 total, and
so if I were to put a 9 over here, that would give me on the right side 18 total oxygens.
On the left side 18 total oxygens as well. So that would be a perfectly balanced equation.
And so that's kind of my starter's guide on how to balance equations. Remember you can
only add the coefficient. You can never change the subscripts. And if you get confused, start
imagining them as molecules and even draw them out if you have to and that might help
a little bit. So I hope that's helpful and have a great day.\
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