4.09 Solubility Equilibria

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来自 University of Kentucky 的课程

高级化学

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University of Kentucky

高级化学

354 个评分

A chemistry course to cover selected topics covered in advanced high school chemistry courses, correlating to the standard topics as established by the American Chemical Society. Prerequisites: Students should have a background in basic chemistry including nomenclature, reactions, stoichiometry, molarity and thermochemistry.

从本节课中

Aqueous Equilibria

This unit continues and expands on the theme of equlibria. You will examine buffers, acid/base titrations and the equilibria of insoluble salts.

4.01 Buffers and the Common Ion Effect10:01

4.02 pH of Buffer Solutions14:04

4.02a Aqueous Equilibria Worked Example 13:58

4.03 Buffer Action25:21

4.03a Aqueous Equilibria Worked Example 25:22

4.03b Aqueous Equilibria Worked Example 35:11

4.04 Buffer: Preparation and Capacity8:45

4.05 Strong Acid - Strong Base Titration17:20

4.06 Titrations Involving Either a Weak Acid or a Weak Base36:45

4.06 Part 1 Aqueous Equilibria Worked Example3:46

4.06 Part 1.a - Aqueous Equilibria Worked Example4:06

4.06 Part 1.b - Aqueous Equilibria Worked Example4:55

4.06 Part 1.c - Aqueous Equilibria Worked Example4:21

4.06 Part 1.f Aqueous Equilibria Worked Example8:01

4.06 Part 1.h Aqueous Equilibria Worked Example3:57

4.06 Part 2.a Aqueous Equilibria Worked Example8:25

4.06 Part 2.b Aqueous Equilibria Worked Example5:53

4.07 Polyprotic Acid Titrations5:53

4.08 Indicators10:19

4.09 Solubility Equilibria4:50

4.10 Molar Solubility and the Solubility Product10:37

4.10.a Aqueous Equilibria Worked Example2:20

4.11 Molar Solubility and the Common Ion Effect7:20

4.11 2.b - Aqueous Equilibria Worked Example4:42

4.11 2.c Aqueous Equilibria Worked Example3:45

4.12 The Effect of pH on Solubility7:07

4.12.b Aqueous Equilibria Worked Example3:42

4.12c Aqueous Equilibria Worked Example3:30

4.13 Precipitation Reaction and Selective Precipitation15:03

4.13a Aqueous Equilibria Worked Example9:05

与讲师见面

Dr. Allison Soult
Lecturer
Chemistry
Dr. Kim Woodrum
Sr. Lecturer
Chemistry

With this learning objective, we are going to be learning a whole new world

of heterogeneous equilibria.

We are leaving behind the acid/base equilibria we have done

all the way through the previous unit with Dr. Solt.

And the first several learning objectives of this unit.

We are now ready to enter

a world of where there will be a solid

in an aqueous solution, both combined.

And we are going to be studying

the world of insoluble salts.

We are going to learn how to write

the reaction for the dissociation of these insoluble salts. We are going to learn how to write

the reaction for the dissociation of these insoluble salts.

We call it a solubility equilibria.

We are going to write an equilibria constant expression for

these reaction, which we call the law of mass action.

So lets begin by

talking about insoluble salts.

Earlier, now when I say earlier I would mean before you talking about insoluble salts.

Earlier, now when I say earlier I would mean before you

ever even began working through the lessons with us

you would have learned about insoluble salts

it is how some salts are insoluble.

You learned law or rules to help govern

which salts are soluble and which salts are insoluble.

But when you have these insoluble salts

it does not mean, that nothing dissolves But when you have these insoluble salts

it does not mean, that nothing dissolves

in solution. It means that just a very very

tiny amount will dissolve.

So we are going to have an equilibrium

exist between the undissolved salt

and the small amount of salt that does

dissolve, and that is what we are going to be considering.

In this learning objective and the next

several through the rest of this unit.

So here is an example of an insoluble salt.

It is silver chloride.

When it dissolves in water

we are going to be able to write this reaction. When it dissolves in water

we are going to be able to write this reaction.

We have, and this is the way we always will write it,

we will put the solid on the left

as a reactant,

and we will put the ions it breaks apart into as a reactant,

and we will put the ions it breaks apart into

on the right, as products.

Now this is a reversible reaction so it

could be written the other direction. Now this is a reversible reaction so it

could be written the other direction.

But we never will, because when we

start studying this

process, we are going to be using equilibrium constants that we are

going to look up in tables and they always apply to the reaction written

in this fashion.

So if we have this reaction written up at the top

you should be able to write the equilibrium constant expression

or the law of mass action, for this reaction.

So choose the right answer.

Well if you selected answer B, then you are correct.

We would not include the silver chloride

in this because it is a solid and you never

include the solids when you write these expressions.

This equilibrium constant we are going to give a

subscript of SP. So we have seen K_a's

K_b's, K_w's

we have seen K_c's and K_p's

this is K_sp and _sp stands for solubility product.

Because it is a product

of the ions that have dissolved into the solution.

There is a table, a solubility folder

of solubility product, provided for you in your resource folder

for this MOOC, and you will be able to

look up values when they are needed.

So once you have one of these equilibrium constant expressions

we can do all the same types of calculations we have done with any other

equilibria problem that we have seen.

Throughout the units we have been covering on equilibria.

So lets try one.

No, no lets not try one, lets work on this guy

practice writing out expressions.

Here is a reaction is Magnesium Chloride.

The first thing you need to be able to write

is the reaction itself.

So remember you put the solid on the left and the ions

it breaks apart into on the right, you give it a try.

Did you write this?

Did you remember that there are two

Chlorides and not write it as Cl_2?

It is It is not the element, it is the

they are the ions. The mono-atomic ion.

So you have 2 of the Cl-'s.

So once you have that, you would be able to write So you have 2 of the Cl-'s.

So once you have that, you would be able to write

this expression.

The law of mass action for this reaction.

Hopefully, you tried it out and wrote this.

It has the _sp for the solubility product.

And we have the magnesium to the first power

and because there is a 2 here we would have

the chloride to the second power.

So this is the ends of our learning objective

number 9, it was a very short lesson.

But I would like you to be able to take

any insoluble salt

and write the reaction, as we did here in this problem

and also write the equilibrium constant expression or the law of

mass action for that.

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