Solubility Constants: Ksp
Ionic Compounds that are water soluble break apart into their ions and create a solubility constant (Ksp).
Ksp is the amount that can be dissolved in a given amount of water – it tells when the solution is saturated The smaller the Ksp, the less soluble the substance
Ksp is written exactly like Keq!
Write the solubility constant for Mg(OH)2
Solubility constants for several compounds are on page 578 in the chemistry book!
Solving for the concentration
The mole to mole ratio of Ag+ and I- are the same, so algebra can be used to solve for the concentration
Calculate the solubility of CuCO3
Write the solubility expression for Mg(OH)2
Solve for OH- and Mg2+
What is [OH-]?
Predicting Precipitates When the concentrations of ions are given, you can solve for the solubility. The number you solve for is called Qsp You can compare your number to the Ksp or the maximum amount that can be disolved
Comparing Qsp and Ksp Qsp < Ksp : the solution is unsaturated and no precipitate will occur Qsp = Ksp : the solution is saturated and no precipitate will occur Qsp > Ksp : the solution is saturated and a precipitate will occur
Predict if a precipitate will form if a PbCl2 solution has a Ksp of 1 Predict if a precipitate will form if a PbCl2 solution has a Ksp of 1.7 x 10-4. The concentration of Cl- is 0.005M and the concentration of Pb2+ is 0.01M.
Answer