1. Aqueous Systems Ks and Solubility expressions

2. So far we have recalled…  Definitions of equilibrium reactions  Factors that can affect the position of an equilibrium – concentration, temperature and temperature and the speed of an equilibrium – catalyst.  How to calculate the reaction quotient Q using concentration of a solution  Definition of a saturated solution.  What Q s and K s mean….  G:\TGHS\Year 13 Chemistry\3.6 aqueous\soluble-salts_en.jar G:\TGHS\Year 13 Chemistry\3.6 aqueous\soluble-salts_en.jar

3. “K s ” vs “s”  Ks is called the solubility product  Tells us the equilibrium position for a saturated solution.  A large K s means the compound is highly soluble as there are many aqueous ions in the solution.  A small K s means the compound is not very soluble in water. We call these solids “sparingly soluble” eg: Ca (OH) 2 – limewater is an example of a sparingly soluble compound.  K s is a constant value for a particular salt at 25 o C  s is the opposite of K s and refers to the solubility of a salt expressed in mol L -1. It is the maximum concentration of a compound at 25 o C that can exist (ie: the concentration required to make a saturated solution).  The good news is…we have some shortcut formulae to calculate both Ks and s.

4. K s formulae  For an AB type salt:  K s = s 2  For an A 2 B or an AB 2 type salt:  K s = 4s 3  (where s is the maximum concentration in molL -1 )  To convert gL -1 to molL -1 simply divide gL -1 by the molar mass.

5. Practice Time

6. “s” formulae

7. Practice time

8. Get practising  Pg 224 Q 1-7