and it finally gets there. Once it

establishes equilibrium what is going to be the value

of the standard delta G. Will it increase to get equilibrium?

Will it have decreased to get to equilibrium? Or will it stay the same?

Students often miss this.

So don't feel bad if you didn't you've got to get to the

understanding of why would stay the same. A standard delta G

is a snapshot of where where it would be

if everything were at one atmosphere. So standard delta G never changes.

Its value is the - 190.5 kilojoules per mole for this reaction.

So as a reaction release these one atmosphere conditions

we no longer have a standard state condition

but the standard delta G is the snapshot of what it is when everything is that.

So don't think that your standard delta G is going to change.

Which Delta G without the circle

it certainly will change. So our next question is to think about

what is happening to Delta G. Once

you establish equilibria. Will it be positive will be negative?

Will be equal to 0. Well it you said it would be equal to 0 you are correct and that's exactly what happens.

Delta G equals zero an equilibrium.

Not standard delta G the only way

standard delta G could equal 0

is if when everything was that was at one atmosphere

this thing happened to be at equilibrium. Very, very unlikely.

Very unlikely. Well this reaction certainly isn't it had a negative value

we know it wi'll proceed to the right. We will build up more and more

of these two. We will use up some of this and some this and finally get to equilibrium.

When he gets the equilibrium, at that point

the Delta G for the reaction is no longer standard state conditions

is 0, That is true for every reaction it's Delta G is equal to 0

at equilibrium. So what happened to the Delta G?

The Delta G started out when we were all at one atmosphere

with this number. It gets to equilibrium

Delta G non-standard is equal to 0

so the negative Delta G is increasing

as the reaction keeps working its way closer and closer

to equilibrium. Now we will look at the mathematical relationship between the standard

in a non-standard delta G, there is a connection. So anytime you need in

non-standard delta G

is when you're not in standard state conditions.

We have this equation help us get to a non-standard.

So if we want to know what the reaction was at

going to proceed to the right or proceed to the left and we had conditions other than

standard state conditions

then this is the equation that we would use. The R that we use in this equation

is the 8.314 because it has the

energy unit a joule, and you actually probably have to convert it to

kilojoules before you could add those terms together.

We see that a Kelvin is here in this K and that's what we have to use for the temperature

and our Q is a reaction quotient.

The reaction quotient if we remember for reaction is just like a K

equilibrium constant. Its products and concentrations if there aqueous

pressures if it is

gases, but its products over reactants

raised to the power of their coefficients. So there's some coefficients of the

balanced equation is raised to those powers.

So that's what the reaction quotient is so

we can look at this reaction and say OK at this point in time

there is this much product, there is this much reactant. Let's put those numbers in there

and let obtain a value for a non-standard

delta G. Now if everything were 1 then Q would be 1.

And if Q is one the natural log of Q is 0 and this term goes away

and that make sense.

So we're just gonna think through this equation.

In terms of what how does change in Q affect the Delta G?

So let's start with a standard Delta G that's negative.

This means that the reaction is spontaneous in the forward direction.

if you we in standard state conditions. We put everything in a

reaction chamber

and this is kinda like our little questions that we went through

are standard delta G was negative the reaction spontaneous in the forward direction.

So the question is what would happen, we have to do, in terms of conditions?

What would we have to do in terms of Q here in order to make Delta G positive?

Well if the delta G is positive we know that it's no longer spontaneous in the forward

direction is now spontaneous the reverse direction.

How do we make Delta G positive? Well, the only way we can make delta G positive

is to make this term positive.

Well this term is positive when Q is what? How do we make the natural log of Q

be positive value? Well

if Q is greater than one

it's a value that is bigger than one then the national log of Q is positive.

That is the first thing. As long as Q is greater than 1 then when we take the natural

log it will be positive in this term

that I have circled up there is going to be a positive term. We just gotta make

positive enough.

So anytime that the products are greater than the reactants because remember what Q is?

It is products over reactants.

Remember? Raised to the power of their coefficients.

So anytime products is greater than reactants

then the Q is going to be bigger than 1 and a national log of Q will be a

positive value

and we can get it positive enough to overcome all the negative that we have here.

We can turn a reaction that was spontaneous in the forward

direction to be spontaneous instead

in the reverse direction. Well lets go through that same mathematical logic

in the revers. What if the standard up to G was positive

the reaction is not spontaneous in the forward direction

it is only spontaneous in reverse reaction direction

if everything were under standard state conditions.

So we start everything is standard state conditions. We know the reactions going to proceed

to the left. That is when a positive

means its spontaneous in the reverse direction.

What conditions would we have to have in order to make

this negative. We want this reaction proceed in the forward direction

instead of in the reverse direction. Well lets think about what has to happen to this term.

In order to make this reaction becomes spontaineous the forward direction

this term is going to have to be very negative. It is going to have to be negative enough to

overtake the positive of the standard delta G.

How can we make that term negative?

Well, the only way we can affect that term R cannot change it's always the same.

Temperature is Kelvin and there's no such thing as a negative Kelvin so the only

way we can make this term negative

is to make the natural log of Q negative.

So if Q is less than one, it is a fraction

less than 1. Then anything can you take the natural log of a number less than 1

its negative. So how do we make Q less than one?

Once again we remember that Q is products

over reactants raised to the power their coefficients.

As long as you have a lot of products so this is a big number.

and this is a small number. So products

is an smaller than the reactants and you want to have a number

less than 1 and as long as it is small enough

this natural log of Q would be negative enough that we would

have more negative than we have positive and that would make my

non-standard delta D negative and we can for force this reaction to become spontaneous

in the forward direction. Now you going to

be doing mathematics numbers for this it's not a big deal.

You just gotta watch for signs if you're given a standard delta G

and they want to know a non-standard delta G this is the equation you will pull out.

Watch you units if Delta G which is typically in kilojoules is given to you

and then we're going to have to make sure that this term gets converted

kilojoules before we convert it.

The thing you have to watch is your T and make sure it is in Kelvin.

Then you will be able to easily convert between a standard delta G

and a non-standard delta G.

So this is the enough are learning objective number 9 in which we are

seeing the connection between the Standard delta G and a non-standard delta G.

We see that they're not the same thing we have to understand their differences

and we have an equation that will help us

convert between them.