|Equilibrium Applications - Solubility|
|Equilibria In Saturated Solutions of Slightly Soluble Substances|
|This unit does not deal with substances that dissolve
water or other solvents. Anything that dissolves at least 1 g/100 mL of
solvent is considered to be soluble. This unit deals with substances
are slightly soluble to those that are considered to be insoluble
to dissolve easily in a solvent). There are also some questions related
to precipitates (slightly soluble substances) that are of interest to
|Some of these questions are:
1) How can the approximate solubility of a precipitate be calculated?
2) How can we predict whether or not a precipitate forms when two solutions are mixed?
3) Which reagents or methods can be used to dissolve precipitates?
|The Solubility Product and Precipitate Formation|
|Consider a saturated solution of silver chloride.
The equilibrium can be represented by: AgCl(s) <=====> Ag+(aq) + Cl-(aq)
|The equilibrium law expression is: Ksp =
|eg. Calculate the [Ag+] and [Cl-] in
solution of the salt at 25oC. What is the approximate
of AgCl in mol/L at this temperature?
|The ions Ag+ and Cl- react
together on a 1:1
basis therefore any AgCl that does dissolve will product 'x' amount of
each of the ions.
|AgCl(s) <======> Ag+(aq) + Cl-(aq)
|Ksp = [Ag+][Cl-]
1.8 x 10-10 = (x)(x)
1.8 x 10-10 = x2
x = 1.3 x 10-5 mol/L
|Therefore 1.3 x 10-5 moles of AgCl dissolves in
1 L of
H2O. The equilibrium 's of Ag+ and Cl-
are each 1.3 x 10-5 mol/L. Since we are dealing with
we can automatically substitute in the units of concentration,
|Determine the solubility of AgI, Ag2CrO4,
and Zn2[Fe(CN)6] in
a) moles/L and b) g/L at 25oC. You will have to refer to the Ksp tables in your databook.