Jenni and Aaron’s…

Solubility

• Solubility is the quantity of a particular substance that can dissolve in a particular solvent (yielding a saturated solution)

• A salt can be considered soluble if >1g of salt can be dissolved in 100mL

• Soluble salts are assumed to dissociate completely in aqueous solution

Henry’s Law: Effect of Pressure on Solubility

• The solubility of a gas in a liquid is directly proportional to the gas pressure

Sg = kHPg

• Sg = gas solubility (M)• kH = Henry’s law constant (M/mmHg)• Pg = partial pressure of the gaseous solute

(mmHg)

Le Chatelier’s Principle: Effect of Temperature on Solubility

• The solubility of gas in a liquid is inversely proportional to the gas temperature– Usually, the gas solubility rxn is exothermic so,

• Gas + liquid solvent saturated solution + heat

energy• A change in any of the factors determining an

equilibrium causes the system to shift– In this case, the reaction shifts left

Solubility Product Constant (Ksp)

• Ksp is a measure of the extent of a salt’s dissociation in solution

• The greater the value of the solubility product of a salt, the more soluble the salt is

• For the Reaction:

AaBb(s) a Ab+(aq) +b Ba+(aq)– The solubility expression is:

Ksp = [Ab+]a[Ba-]b

Reaction Quotient (Q)

• For the Reaction:

AaBb(s) a Ab+(aq) +b Ba+(aq)– The solubility expression is:

Q = [Ab+]a[Ba-]b

• What’s the difference between Q and Ksp?– Q is used for a chemical reaction which is not

necessarily at equilibrium

Q vs. Ksp

• If Q = Ksp, the system is at equilibrium and is saturated (no precipitation)

• If Q < Ksp, the system is not at eq. and is not saturated (precipitation)

• If Q > Ksp, the system is not at eq. and is supersaturated (precipitation)

The Common Ion Effect

• Using: Ksp = [Ag+][Cl-] = 1.6x10-10

• We know: (x)(x) = 1.6x10-10

• And: x = [Ag+] = [Cl-] = 1.3 x 10 -5

• So what if we added 0.10 mol of NaCl to 1 liter of this AgCl solution?

• Hmmm…

Common Ion Effect Cont’d

• The NaCl dissociates completely, so that’s the same thing as adding 1 mol Na+ ions and 1 mol Cl- ions to the solution

• We must take into account the new Cl- ions because of this so-called… “common ion effect”

• Let’s take a look at the expression now[Ag+][Cl-] = 1.6x10-10

[Ag+](0.10M) = 1.6x10-10

[Ag+] = 1.6x10-9

• A complex ion is formed by combination of simpler ions or molecules– Example: Co2+ combines with 6 H2O to form

the complex ion Co(H2O)62+.

Complex Ions Cont’d

Hmmm….

(THE END)