Name____________________per____
Ch. 17 Sec. 6 notes
17.6- Precipitation and separation of ions
Up till now we have placed ionic substances in water so it can
dissociate until it saturated and reaches equilibrium.
Write equation here:
Does a precipitate form when 0.050 L of 2.0  102 M NaF is mixed
with 0.010 L of 1.0  102 M Ca(NO3)2
What compound will precipitate?___________Ksp= _____________
In 0.050 L of 2.0  102 M NaF there are:
Equilibrium can also be reached by mixing who solutions containing
the ions to create a ______________________.
By mixing _____________and _____________together will create a
precipitate of ______________ if the product of the of the ion
concentrations, Q = [Ba2+][SO42-], greater than Ksp.
Write equation here:
Q is referred to simply as the ______________________
Will a Precipitate Form?
In a solution,
If Q ___ Ksp, the system is at equilibrium and the solution is
saturated.
If Q ___ Ksp, more solid will dissolve until Q = Ksp.
If Q ___ Ksp, the salt will precipitate until Q = Ksp.
0.010 L of 1.0  102 M Ca(NO3)2 there are:
Molarity
Plug in numbers into Ksp expression
WALK THROUGH THIS EXAMPLE!!!!!!
SAMPLE EXERCISE 17.15- Will a precipitate form when 0.10 L of
8.0  103 M Pb(NO3)2 is added to 0.40 L of 5.0  103 M Na2SO4?
What precipitate COULD be made?_______________________
Look up the Ksp in Appendix D:__________________________
To determine if PbSO4 will precipitate, we have to calculate the ion
product, Q=[Pb+2][SO4-2] and compare it with Ksp.
In 0.10 L of 8.0  103 M Pb(NO3)2 there are:
In 0.40 L of 5.0  103 M Na2SO4 there are:
Selective Precipitation of Ions
Consider a solution containing Ag+ ions and Cu+2 ions then HCl is
added, AgCl precipitate will form and the CuCl2 is soluble and remain
as ions in solution.
Separation of ions in an aquesous solution by using a reagent that
forms a precipatate with one or few of the ions is called selective
precipatation
A solution contains 1.0  102 M Ag+ and 2.0  102 M Pb2+. When
Cl is added, both AgCl (Ksp = 1.8  1010) and PbCl2 (Ksp = 1.7  105
M) can precipitate. What concentration of Cl is necessary to begin
the precipitation of each salt? Which salt precipitates first?
We have to convert the moles in to molarity but use the combined
volume.
We know that both Ag+ and Pb+2 would form a precipitate with Clbut which will form first?
Lets look at Ag+ with Cl-:
Substitute the values into the Ksp expression and solve for Q
Lets look at Pb+2 with Cl-:
Which concentration is smaller?
This means that it will _________ precipitate as such a _________
concentration verses ________________.
A solution consists of 0.050 M Mg2+ and Cu2+. Which ion
precipitates first as OH is added?
What concentration of OH is necessary to begin the precipitation
of each cation? [Ksp = 1.8  1011 for Mg(OH)2, and Ksp = 4.8  1020
for Cu(OH)2.]
Lets look at Mg+2 with OH-:
Lets look at Cu+2 with OH-:
Which concentration is smaller?
This means that it will _________ precipitate as such a _________
concentration verses ________________.