>> host: Welcome back
to Unit 10 and the third video
on the playlist
for our unit on equilibrium.
Since the expression for Keq
is the ratio of products
over reactants, if there are
fewer products than reactants,
Keq will be less than one.
And of course, if there is
less product than reactant,
Keq will be greater than one.
You might be wondering about
a situation when products
and reactants are about equal
and Keq is close to one.
The concentrations of reactants
and products could be equal
with a value of Keq
that's not exactly equal
to one because of
differing exponents.
But in general,
if an equilibrium value
is approximately one,
the concentrations
of reactants and products
are considered to be
approximately equal.
With that understanding in mind,
let's return to our classroom
where our students are about
to summarize what they now know
about Keq.
>> professor: So,
let's finish up our discussion
about equilibrium constants
by developing a statement
that describes the relationship
of the equilibrium constant
to the relative amounts
of the reactants
and the products.
So write your statements
on a whiteboard and then
we'll share them shortly.
>> student: So we need to
describe a large Keq
and a small Keq mean
in terms of reactants
and products.
>> student: Well, Keq
is products over reactants,
so if there are
a lot of products,
then Keq is large, right?
>> professor: Alright,
let's see what you came up with.
Who would like to share
their work?
>> student: We will.
We just said that if Keq
is large, then there are
more products than reactants.
And if Keq is small,
there are more reactants
than products.
>> professor: Good!
Well What did you guys
come up with?
>> student: That's pretty much
what we said.
We just added values
to our statement.
>> student: Right. We said
that if Keq is less than 1,
reactants are at a higher
concentration at equilibrium.
If Keq is greater than 1,
products are at a higher
concentration at equilibrium.
And if Keq is close to 1,
then the concentrations
of reactants and products
are about equal.
>> professor: Good job.
So let's summarize
what we've learned so far
about equilibrium.
Now what I'd like to do
is just go around the table
and each person mention
one thing that they've learned.
So Danica, why don't we start
with you.
>> student: Sure. A reaction
has to be reversible
to reach equilibrium.
>> student: On the rate of
the forward reaction has to be
the exact same as the rate
of the reverse reaction
to be at equilibrium.
>> student: We can find out
if a reaction makes
more products or more reactants
from the equilibrium constant,
Keq.
>> student: Keq is a constant
as long as the temperature
doesn't change.
>> professor: Very good.
Nice summary, everyone.
Now I have a question that
I like to ask
all of my students.
And it is why do you think
that equilibrium is even
relevant in our daily lives.
And so I'd like you to think
about it.
Why is equilibrium
so important?
>> host: Another great question!
Why is equilibrium important?
And I'm betting you already
have some ideas in mind.
So let's take a break
and give you a chance
to write down some examples
of systems in everyday life
that are in
chemical equilibrium.
Remember our three key words.
Think of systems
that are stable, balanced
or unchanging.
When you're ready,
and you've come up with
three everyday examples
of chemical equilibrium,
go to the next video
on the Unit 10 playlist.
I'll see you there.