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hi it's mr. Andersen and this is

chemistry essentials video 70 it's on

Hi. It's Mr.Andersen and this is chemistry essentials video 70. It's on solubility. You've

solubility you've probably noticed that if we add salt to water it will dissolve but if we add more salt and more salt

probably noticed that if we add salt to water it will dissolve. But if we add more salt

and more salt eventually it doesn't dissolve any more

and more salt and more salt eventually it doesn't dissolve anymore. And so what's going

and so what's going on well if we look down at the atomic level we're adding a salt grain and that's made up of all

on? Well if we look down at the atomic level we're adding a salt grain. And that's made

these ionic bonds sodium and chloride

up of all of these ionic bonds, sodium and chloride. And they're going to break apart

and they're going to break apart into their aqueous ions they're going to be assured away by the water that's going

into their aqueous ions. They're going to be ushered away by the water. That's going

to increase the concentration of those ions in solution and so if we increase increase increase the amount of ions

to increase the concentration of those ions in solution. And so if we increase, increase,

eventually no more ions can be added and

increase the amount of ions, eventually no more ions can be added. And so that's going

so that's going to push it back to this more solid form of salt and so if we

to push it back to this more solid form of salt. And so if we look at a solution, remember,

look at a solution remember we're dissolving a solute in a solvent and so you can think of that solute as a solid

we're dissolving a solute in a solvent. And so you can think of that solute as a solid.

if it's all chemically bonded together and if we can break it apart into its

If it's all chemically bonded together and if we can break it apart into its ions then

ions then its dissolved in solution and so if we think of on the left side of

it's dissolved in solution. And so if we think of on the left side of our equation we have

our equation we have the solid form and on the right side we have it broken apart into its ions and so really in a

the solid form and on the right side we have it broken apart into its ions. And so really

solution we have a reversible reaction it's going to have its own equilibrium

is a solution we have a reversible reaction. It's going to have its own equilibrium constant.

constant and we'll call that KSP which is essentially the solubility product

And we'll call that Ksp which is essentially the solubility product constant. And that's

constant and that's a way to measure the solubility of any kind of a salt and so

a way to measure the solubility of any kind of a salt. And so there are a few things that

there are a few things that are going to affect the solubility one of the big ones is going to be Delta G in other

are going to affect the solubility. One of the big ones is going to be delta G. In other

words it's going to be the enthalpy it's going to be the entropy of the system

words it's going to be the enthalpy. It's going to be the entropy of the system. Let's

let's say that they're really intense bonds between these in the solid form

say that they're really intense bonds between these in the solid form, it's going to be

it's going to be hard for those to break apart into their ions likewise as we change what is in the solvent if we add

hard for those to break apart into their ions. Likewise as we change what is in the solvent,

more ions to it it's harder for more ions to be added we could also change

if we add more ions to it, it's harder for more ions to be added. We could also change

the pH and that's going to affect what can be dissolved as well now there are a

the pH. And that's going to affect what can be dissolved as well. Now there are a few

few things that dissolve readily in water that you should simply know those

things that dissolve readily in water that you should simply know. Those are going to

are going to be the ammonium ions potassium ions sodium ions and then also the nitrate anion as well and so if we

be the ammonium ions, potassium ions, sodium ions. And then also the nitrate anion as well.

look at sodium chloride breaking down in water as a reversible reaction on the

And so if we look at sodium chloride breaking down in water as a reversible reaction, on

left side we're going to have the solid

the left side we're going to have the solid form. On the right side we're going to have

form on the right side we're going to have the two ions that are in aqueous environment remember we're breaking those apart a

the two ions that are in aqueous environment. Remember we're breaking those apart. A wonderful

wonderful simulation to look at this is the pH et on salts and solubility and so

simulation to look at this is the PHET on salts and solubility. And so I'll put a link

I'll put a link down below but basically I'm going to add a little bit of salt

down below. But basically I'm going to add a little bit of salt and we're going to look

and we're going to look at this at the atomic level and so what's going to happen is the waters assuring those ions

at this at the atomic level. And so what's going to happen is the water is ushering those

away and so we're going to break it apart into its cation and its anion

ions away. And so we're going to break it apart into its cation and its anion. Let's

let's say a radically increase the number of ions what's going to happen

say I radically increase the number of ions, what's going to happen? Well you can see that

well you can see that most of them are going to be in solution but some are going to go back to that solid form

most of them are going to be in solution. But some are going to go back to that solid

there's simply too many ions out there and so we've pushed it more towards the

form. There's simply too many ions out there. And so we've pushed it more towards the right

right side of this reversible reaction now let's look at a different salt so

side of this reversible reaction. Now let's look at a different salt. So now we've got

now we've got silver bromide if I were to add 200 of the cations to this we're

silver bromide. If I were to add 200 of the cations to this we're going to see a different

going to see a different kind of an effect what's happening is that they're all going back to that solid form so if

kind of an effect. What's happening is that they're all going back to that solid form.

we were to look at this equation up here it's shifting it back more towards the

So if we were to look at this equation up here, it's shifting it back more towards the

left and so how do we measure does a reaction go to the right or does it go

left. And so how do we measure, does the reaction go to the right or does it go to the left?

to the left remember that's going to be our equilibrium constant and so if we

Remember that's going to be our equilibrium constant. And so if we were to look at the

look at the equilibrium constant of sodium chloride being dissolved in water we could set it up like this where it's

equilibrium constant of sodium chloride being dissolved in water we could set it up like

going to be the concentration remember of the two products over the

this, where it's going to be the concentration remember of the two products over the concentration

concentration of that reactant now we can get rid of that reactant since it's a solid so our KSP value is going to be

of that reactant. Now we can get rid of that reactant since it's a solid. So our Ksp value

thirty seven point three what does that mean since it's much greater than one

is going to be 37.3. What does that mean? Since it's much greater than 1 that's going

that's going to shift it way towards the right we're going to have way more of those ions if we compare that to the

to shift it way towards the right. We're going to have way more of those ions. If we compare

silver bromide what's our KSP value here it's going to be much less than one what does that

that to the silver bromide, what's our Ksp value here? It's going to be much less than

mean our equation is going to be shifted way towards the left and so we're going

1. What does that mean? Our equation is going to be shifted way towards the left. And so

to have more of that solid form and so the neat thing about this simulation is

we're going to have more of that solid form. And so the neat thing about this simulation

you can play around with the KSP values now I've got a theoretical salt with

is you can play around with the Ksp values. Now I've got a theoretical salt with cations

cations and anions and I'm simply going to lower the KSP value you can see as I

and anions and I'm simply going to lower the Ksp value. You can see as I lower it it's

lower it it's starting to move back more towards the left it's moving back more towards that solid form so if you have a

starting to move back more towards the left. It's moving back more towards that solid form.

really low KSP value it's going to be

So if you have a really low Ksp value it's going to be shifted towards the left. If I

shifted towards the left if I radically increase KSP and it goes way back more towards the right or in aqueous solution

radically increase Ksp and it goes way back more towards the right or in aqueous solution.

and so that's what what KSP effects but you should be thinking like why does it

And so that's what Ksp affects. But you should be thinking why does it affect that? What

affect that what effects KSP well it's mostly going to be Delta G so changes in

affects Ksp? Well it's mostly going to be delta G. So changes in enthalpy and changes

enthalpy and changes in entropy and so if we look at the solid form remember

in entropy. And so if we were to look at the solid form, remember there are going to be

they're going to be ionic bonds between all of these and the greater those bonds

ionic bonds between all of these, and the greater those bonds are it's harder to break

are it's harder to break them apart and then move it away into solution and so also they're going to be interactions

them apart and then move it away into solution. And so also they're going to be interactions.

once it does get broken away it's going to interact with the solvent itself and

Once it does get broken away it's going to interact with a solvent itself. And let's

let's say there are already a lot of ions in solution it's harder to be added

say there are already a lot of ions in solution, it's harder to be added. And we could also

and we could also change for example the pH of that solution increase or decrease

change, for example, the pH of that solution, increase or decrease the number of protons,

in the number of protons and that's also going to change how it interacts with the solvent now we basically just talked

and that's also going to change how it interacts with the solvent. Now we basically just talked

about enthalpy remember entropy is going to be an important part of this as well

about enthalpy. Remember entropy is going to be an important part of this as well. And

and that's why it's better to look at the whole Delta G and so what are some

that's why it's better to look at the whole delta G. And so what are some applications

applications of this well let's say we have sea water and fresh water and we're

of this? Well let's say we have sea water and fresh water. And we're going to try to

going to try to dissolve salts in each of those it's going to be different because in seawater we're going to have

dissolve salt in each of those. It's going to be different. Because in sea water we're

all of these ions already present sodium chloride sulfate magnesium all of these

going to have all of these ions already present. Sodium, chloride, sulfate, magnesium. All

are already there and so it's hard for us to add more of those salts into

of these are already there. And so it's hard for us to add more of those salts into solution.

solution what's another application of this acid mine drainage so how did this get so nasty well there was probably a

What's another application of this? Acid mine drainage. So how did this get so nasty? Well

coal mine at some point that had a lot

there was probably a coal mine at some point that had a lot of sulfur in it, which combined

of sulfur in it which combined with water and made sulfuric acid and as it drained through this area that decrease

with water and made sulfuric acid. And as it drained through this area that decreased

the pH and so there's all of a sudden a lot of ions in solution mostly iron hydroxide what happens as it's now

the pH and so there is all of a sudden a lot of ions in solution. Mostly iron hydroxide.

settled out is we're adding more fresh water to it it's increasing the pH at

What happens as it now settled out is we're adding more fresh water to it. It's increasing

this point we can't hold those in solution and now all of these ions all

the pH at this point. We can't hold those in solution and now all of these ions, all

this nasty iron is coming out of solution or we could look at acid rain

this nasty iron is coming out of solution. Or we could look at acid rain. What's happening

what's going to happen in there is we're decreasing the pH and that changes the

there is we're decreasing the pH and that changes the amount of carbonate that we can

amount of carbonate that we can actually dissolve and so did you learn to predict the solubility of assault or ranked its

actually dissolve. And so did you learn to predict the solubility of a salt or rank its

solubility given the KSP values remember the lower it is the more likely its be

solubility given the Ksp values? Remember the lower it is the more likely it will be

in the solid form or shifted more towards the left the greater it is and

in the solid form or shifted more towards the left. The greater it is the more it's

more it's shifting towards the right also could you interpret data based on a

shifting toward the right. Also could you interpret data based on a Ksp value? How is

KSP value how is that going to behave and then finally can you look at what's going on inside the solid and inside the

that going to behave? And then finally, can you look at what's going on inside the solid and inside the ions in relation to the solvent to predict our Ksp values? I hope so. And

ions in relation to the solvent to predict our KSP values I hope so and I

hope that was helpful

I hope that was helpful.