Post on 17-Dec-2015
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)