Lecture Equilibrium

everybody welcome Teoh Our decision on equilibrium ums running the

time out what equilibrium means some examples on and then

also how we affect equilibrium.

Eso What we're talking about is dynamic equilibrium is supposed

to static equilibrium.

So essentially what that means dynamic means that things they're

still moving.

So feeling of this kind of like a real world

example If you have ever tried to walk the wrong

way on an escalator, I'm sure you guys never done

that. But if you have and if you're successful in

getting just the right speed of you walking to match

the escalator so it kind of looks like you're standing

still. That's a good example of dynamic equilibrium.

So if someone would you just look at just you,

it looks like you're not moving.

But in all reality, you and the escalator are both

moving. But just at the same rate in opposite directions,

I'm so that's basically what we're looking at with dynamic

equilibrium. So we're gonna be looking at chemical equilibrium.

So as in chemical reactions, unusually, most chemical reactions are

reversible, meaning they can go forward and reverse.

So there's some that aren't like combustion, you know, I'm

burned something.

But most other reactions are reversible.

Scathing about, like forming and decomposing water.

We did both of those with the electrolysis and the

experiment. So those air reversible reactions think you can do

them and take the products and turn them back into

reactive. Um, so when a reaction is reversible, instead of

just using a forward arrow like we do in a

normal chemical reaction, we use a double headed arrow to

show that both reactions are happening forward and reverse at

the same time.

So if you look at this example, if we have

nitrogen los hydrogen making ammonia that's exo thermic releases 92

killer jewels the reverse of that would be taking those

92 killer jewels and ammonia to make nitrogen and hydrogen.

So who put that together?

We just We usually write it as the forward reaction,

but then you stick the reverse arrow in there to

show that it's reversible.

So some properties of equilibrium.

So again, we're kind of focusing on chemical equilibrium at

this point.

But the big thing about any system in equilibrium is

it has to be a closed system, meaning nothing can

get in or out.

Um, so if you think about a good example of

this is like a water bottle, if you have a

water bottle really partially filled and you see old, it's

always been of the same amount of water and some

of it may evaporate and be up the water bottle.

So making dents on the sides you'll see those droplets,

Um, but yourself, the same amount of water going in

back and forth between liquid and gas.

If you leave a water bottle open on the table

eventually, it will not have any good water in it

anymore. Because of all referee eso.

In order for something to be able to achieve that

equilibrium, it has to be sealed off.

It has to be quote, um, one of the big

things about equilibrium in these next two things are probably

the most important part.

Um, so initially, in a reversible reaction, you're just going

to have reactive.

You start with a whole reactive, um, and they're gonna

be starting to be used up and create products normal

forward reaction.

So starting with the reactant, you're gonna go forward until

you make products eventually ease.

There's gonna be enough products that they can start reacting

with themselves and so start going back.

So eventually the reverse reaction is are increasing.

Um, so you're still making taking reactant making products with

the forward reaction, taking some products, making captains.

Eventually you're going to get to a point where you

have they're gonna be going back and forth at the

same rate.

So every time a reactive gets made a product, let's

put back into a reactive reacting is made product.

It's turned back into a reactive eso.

Eventually, the rates are gonna end up being the same

again. Think about yes later.

Initially, you're like president of the escalating really fast, and

then eventually, like, gets just the right speed, and you

and the escalator are going at the same.

Great. So that's what's going on in this graph here.

The forward rate initially is going pretty fast.

Is all you have is reactive sits in a start,

slowing down as use it up reactive.

The reverse rates gonna start zero.

You know how many products, but it's gonna start speeding

up until they get the same rate.

And when that happens, if you rates are the same,

the amounts of reactions and products.

They're going to stay constant, not necessarily equal, but constant

because every time you use up a reactive A product

is gonna get turned back into a real.

So you're concentrations end up staying constant.

Um, because the there being used up justus fasters, they're

being made or vice versa.

Um, so you start with just reactive, because this usually

what you start with all reactive, you're gonna slowly decrease

the amount of reactive.

And still, until it levels off products, they're gonna start

a zero increase until they level off.

So this flatline and the concentrations is a very strong

indicator that you delivery of has been achieved cause the

concentrations are not doing anymore because your rates are equal

to each other.

All right, um, so those air chemical reaction equilibrium a

couple others that want to mention just really briefly one

is phase equilibrium.

So that's kind of like the water bottle situation that

I talked about.

Normally, phase equilibrium happens at a face change temperature.

So if you have water boiling at 100 degrees in

a closed system, um, the rate that the water is

boiling actually equals the read that water is, um, convincing

back down.

So you end up with this equilibrium, and that can

happen at any phase.

Change temperatures if you keep water at 100 degrees, just

like set.

Um, you'll have ah, phase equilibrium.

If you had water s a zero degrees.

Then, um, you would have this situation eso as your

degrees for water if you could hold water as your

degrees. The rate that the solid water is melting actually

ends up equaling the rate that the liquid water is

freezing against.

You end up with this phase equilibrium.

That would be true for any substance at its melting

or boiling point, you can get a phase equilibrium.

Um, solution.

Equilibrium is the other thing.

We'll talk more about solutions in the next two weeks.

So but this is table Jay Ritter.

Sorry. Table G in the reference table.

Um, so a saturated solution, meaning it has, like the

perfect amount of stuff dissolved is gonna have an equilibrium

as well.

So the rate of it saturated means it's perfect amount

seem they have a little bit like left over at

the bottom, and they rate that the left over in

the bottom is dissolving into the solution equals the rate

that some of the stuff is precipitating back out.

So you end up with the same amount of stuff

dissolved. But this kind of constant back and forth, I'm

so looks kind of like that.

So the solid eventually isn't start dissolving, and then you'll

get to the point where the dissolving and reforming the

solid each other Great.

So once you have an equilibrium, this is baseless.

And half of this topic months, you haven't equilibrium.

You can start bumping it and shifting it.

The thing about systems equilibrium, they like to stay at

equilibrium. So if you apply some sort of stress to

it, too, mess up the equilibrium, going to try to

give back to that equilibrium date.

Um, so when you shift an equilibrium, it's going to

temporarily favor either the Florida reverse reaction to try to

get itself back to thank you.

That equilibrium state.

Okay, um so kind of Ah, really like simple, straightforward

guideline before we look at an example, if you add

something, it shifts away from that side.

Um, so at a bunch of whatever, it's gonna try

and shift away from that to use it up.

If you take something away, it's gonna shift towards that

to try to fill it back in.

So add away from it.

Take gonna go towards him.

No, look, it s so this is just another way

of looking at that forward shift.

So when I say something shifts to the right or

for reaction shift, that means you're making more products you're

using a pre actives reverse shift or left shift means

you're using a products to make more reactive.

Oh, just so your remember forward is like your normal

reaction if Mr Products reverse is first products factory.

All right, so we're gonna look at this example.

This is the same one I gave earlier in the

presentation. So nitrogen plus two hydrogen makes to ammonia, and

that's in equilibrium.

And the four reaction is Axl Thurman.

So he is a product of the forward reaction.

You're gonna look a bunch of different things you can

do with it.

So if we were to add reacted so either hydrogen

or nitrogen adding reactive means you have too much for

here. Let reactive there's extra on this side of the

equation. So if it's too much over here, the reactions

in a trip shift to use it up, so too

much reactive shift forward to try.

Use up that access.

I'm gonna shift right extra reactant shift right?

So if it's shifting right that for reaction is gonna

use up reactive is to make more products.

So are re other reacting.

Concentrations are going to go down, and our product concentration

is going to go up so the nitrogen and hydrogen

perspectively will decrease as shifts and uses up the reactions.

But the products are going to increase.

Make more ammonia, so adding reactive or a reaction favored

shift to the right.

Adding products does the exact opposite.

Now, in this case, heat is considered a product.

It's produced by the forward reaction, so adding ammonia or

adding heat does the exact same thing.

So now you have way too much over on this

side of your reaction way too much product.

It's gonna try to use up on a trip backwards

or reverse to try to use it.

The excess product so adding product shifts, reverse favorite or

shifts the left, so we're gonna make more reactive.

So the hydrogen and nature's entering an increase isn't a

use up any of that ammonia that you add it

So adding products shifts left, use it up.

I'm removing does the opposite.

So if we remove reactive is take away nitrogen or

take away hydrogen Now there's essentially, like a void in

the reaction.

So if you remove reactions is gonna go, you have

to try to fill it back in.

So moving reckons shifts back to the left to try

to make more reactive and fix what you messed up.

Um, essentially.

So when you shift that left, it's gonna use up

on the ammonia that you had.

So the ammonia concentrations going to decrease, But it's gonna

feel back in the nitrogen and hydrogen, those air gonna

increase. So removing reactive reverse reaction is favored shifts to

the left.

Ruling products will do the exact opposite.

So if you take products away again, there's gonna be

kind of a gap there, so it's gonna shift forward

to try a fill in those reacted products back in.

So move products forward reaction is favored.

So you're gonna use up your reactive so your nitrogen

and hydrogen are gonna decrease.

You produce some more ammonia or some more energy that

you took away it so bad shift to use it

up. Move.

It's gonna shift to fellow HVAC units if you removed

products shift or were to fill it back in, remove

reactive. Just reverse to fill that back it pressure is

a little bit different.

Eso pressure only affects their first of all on and

it's usually done by changing the volume.

So if you remember back from gas laws, if you

decrease the volume of a gas, that's going to increase

the pressure.

If you expand the volume, then it relieves the pressure

decreases the pressure.

Um, And if you think about gas molecules, they don't

like being ALS motion together.

Gas molecules like being spread out, they need space.

They have a lot of kinetic energy.

So if you compress a gas or you increase the

pressure, it's gonna try to shift to relieve that pressure

by getting less gas monkey fuels.

Okay, so if you're looking of all together, they're gonna

trash if they have less gas molecules, if there's less

things in there, then they each have more space.

So in this case, if we look at this reaction

on the reactive side.

We have nitrogen and 200 ins.

We have three gas molecules on the reactant cyber willing

to ammonia on the product side.

So if you're smushed into a tiny space, you'd rather

be with just another person, then to other people.

So their mouth the reaction is going to shift this

way to try to make less gas molecules as you

smush the men and increased that pressure.

Okay, decreasing the pressure would do the opposite.

I'm so view.

Increase the pressure.

It compresses the gas molecules into a smaller space.

They're gonna try to relieve that stress by shifting to

the side with fewer gas molecules.

If you decrease the pressure, they can expand back out,

shift back to the side with more gas molecules.

So pressure you really you're just counting molecules last one

to mention really quick, because it doesn't really do anything

in kinetics.

We talked about a catalyst because it lowers the activation

energy that's gonna lower both activation energies.

So there's not actually a shift at all when you

add a catalyst because it's just making both reactions go

fast. So there's equilibrium.

Let me know what you guys have for questions, and

I will talk to you later

Lecture Equilibrium

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