Catalyst

•It is found that 1.1 x 10-2 g of SrF2

dissolves per 100 mL of solution. Calculate the solubility product of SrF2.

End

Acetate

Lecture 8.2 – Application of Ksp

Today’s Learning Targets

•LT 8.4 – I can hypothesize about which slightly soluble compound will precipirate first through utilization of the Ksp

Predicting Precipitation

•Recall, the reaction quotient (Q) can be used to determine the direction an equilibrium needs to shift in order to achieve equilibrium:

Q > Ksp: Shift left and precipitate more

Q < Ksp: Shift right and dissolve more

Q = Ksp: Solution is at equilibrium•Therefore, we can predict whether more or

less solid will precipitate based on this answer

Class Example•Does a precipitate form when 0.10 L of 8.0

x 10-3 M Pb(NO3)2 is added to 0.40 L of 5.0 x 10-3 M Na2SO4? Note – the Ksp of PbSO4 is 6.3 x 10-7

Table Talk•Doe a precipitate form when 0.050 L of

2.0 x 10-2 M NaF is mixed with 0.010 L of 1.0 x 10-2 M Ca(NO3)2. KSP (CaF2) = 3.9 x 10^-11

Selective Precipitation•Oftentimes, we have solutions

that contain multiple solubility equilibriums.

•We can selectively precipirate some of the compounds, but not all, by utilizing Ksp

•The smaller the Ksp of an ion, the more likely it will precipitate from solution first.

Class Example•A solution contains 1.0 x 10-2 M Ag+ and

2.0 x 10-2 M Pb2+. When Cl- is added, both AgCl (Ksp = 1.8 x 10-10) and PbCl2 (Ksp = 1.7 x 10-5) can pre. What concentration of Cl- is necessary to begin precipitation of each salt? Which salt precipitates first?

Table Talk•A solutions consists of 0.050 M Mg2+ and

Cu2+. Which ion precipitates first when OH- is added? What concentration of [OH-] is needed to begin to precipitation of each cation? NOTE – Ksp of Mg(OH)2 is 1.8 x 10-

11 and Ksp of Cu(OH)2 is 4.8 x 10-20.

Drill Baby Drill

•Drill – Calculating Molar Solubilities

•Drill – Predicting Precipitation

•Integrated Practice – Connecting Ksp to past Units

•Read 17.1, 17.4, 17.5, 17.6, and 17.7•Homework: Drills and Integrated Practice•Exam Debrief – Thursday or Friday 3:30 –

4

Closing Time