What does dissociation or dissolution mean

1
What does dissociation or dissolution mean?
2

What does precipitation mean?
3
Write dissociation equations for these salts in
water

• CaCl2 ? Ca2 2Cl-1 Ag2CrO4 ? 2 Ag1 CrO4-2
  MgCO3 ? Mg2 CO3-2

4
What is the solubility product constant
expression?

• The mathematical relationship of reactants at
  equilibrium(Just a simple Keq expression)
  Remember solids are not included in a Keq

5
Why is the concentration of precipitate not
included in the mass-action expression?

• We just said to Remember solids are not included
  in a Keq

6
Write the solubility product expression for

• iron III hydroxide.Ksp Fe3 OH-13 Because
  Fe(OH)3 ? Fe3 3 OH-1
• barium phosphateKsp Ba23 PO4-32

7
How is the value for solubility product calculated

• Find the molar concentration of each ion at
  equilibrium and substitute into the Ksp
  expression

8
What is the value of solubility product constant
(Ksp) for lead II fluoride if 1.9 x 10-3
Moles of lead II fluoride will dissolve in 1
liter of water

• Rules1. Write Equation,
• 2. Write Ksp Expression3. Determine type-(Cal K,
  Cal , will ppt, How much to ppt)

9
What is a net ionic equation?

• an ionic equation with only the ions
  participating in the reaction actually written
  (omit spectators)

10
How do you decide which are ions that
precipitate?

• Look at the solubility table. If it is
  insoluble, it will be the ppt

11
How do you decide which are the spectator ions?

• They are the soluble ones

12
Try a net ionic equation with silver nitrate
ammonium sulfate.

• AgNO3 is soluble so it will dissociate into Ag1
  and NO3-1 (NH4)2SO4 is soluble so it will
  dissociate into NH41 and SO4-2 In a reaction,
  only the positive ions will bond with negative so
  the possibilities are NH4 NO3 and Ag2SO4.

13
Net ionic contd

• Write complete ionic equation first.
• Ag1 NO3-1 NH41 SO4-2 ? NO3-1
  NH41 Ag2SO4

14
Net ionic contd

• Eliminate the spectators
• NO3-1 NH41 are on both the reactants and
  products side so they didnt really participate
  in the rxn. (Equal and opposite cancel)
• Balance what is left and you have the the net
  ionic
• 2Ag1 SO4-2 ? Ag2SO4

15
Another way

• Say the products in words. Ammonium nitrate and
  silver sulfate.
• Look at a solubility table and you will see
  ammonium nitrate is soluble (so it will not
  ppt.spectator, and silver sulfate is slightly
  soluble (which for us means insoluble) so it will
  be a product.

16
Another way contd

• Now write the ions that make silver sulfate (Ag1
  and SO4-2) as the reactants and Ag2SO4 the
  product.
• 2Ag1 SO4-2 ? Ag2SO4

17
What is the common-ion effect?

• When you dissolve a substance in a solution that
  has part of it already there.
• The substance dissolving and the ions in the soln
  already have something in common
• Like dissolving Ag2SO4 in Na2SO4 The sulfate is
  common to both. What this does is essentially
  take up some of the spaces allotted to the
  Ag2SO4 to dissolve. It will always reduce the
  solubility of the dissolving substance

18
Give an example of how it works

• See problem solving

19
What conditions produce a solubility
equilibrium?A pic may help.