Solving Ksp Problems:
Part One - s2Solving Ksp Problems:
Part Two - 4s3Solving Ksp Problems:
Part Three - 27s4Solving Ksp Problems:
Part Four - 108s5Back to Equilibrium Menu
The generic problem is:
Calculate the molar solubility (in mol/L) of a saturated solution of the substance.
I'm going to assume you've gone through the other files first, so the presentations here will be a bit abbreviated.
Example #1: The Ksp of Sn(OH)4 has been determined to be 1 x 10¯57. Calculate its molar solubility.
Solution:
1) Write the dissociation equation for Sn(OH)4 and its Ksp expression:
Sn(OH)4 ⇌ Sn4+ + 4OH¯
Ksp = [Sn4+] [OH¯]4
2) Substitute into the Ksp expression and solve:
1 x 10¯57 = (s) (4s)4256s5 = 1 x 10¯57
s = 1 x 10¯12 M (to one significant figure)
The value for s is the molar solubility of the tin(IV) ion. Since every Sn(IV) ion comes from a dissolved Sn(OH)4 formula unit, the value for s is the molar solubility of Sn(OH)4.
Example #2: Given that the Ksp of Ti(OH)4 is 7 x 10¯53, determine its solubility in grams per liter of saturated solution.
Solution:
1) Write the dissociation equation for Ti(OH)4 and its Ksp expression:
Ti(OH)4 ⇌ Ti4+ + 4OH¯
Ksp = [Ti4+] [OH¯]4
2) Substitute into the Ksp expression and solve:
7 x 10¯53 = (s) (4s)4256s5 = 7 x 10¯53
s = 1.222845571 x 10¯11 M
The value for s is the molar solubility of the titanium(IV) ion. Since every Ti(IV) ion comes from a dissolved Ti(OH)4 formula unit, the value for s is the molar solubility of Ti(OH)4.
3) Determine concentration in grams per liter:
(1.222845571 x 10¯11 mol/L) (115.8946 g/mol) = 1 x 10¯9 g/L (to one sig fig)
Example #3: The log Ksp for thorium(IV) hydroxide has been determined to be -50.52 ± 0.08. What is the molar solubility for Th(OH)4?
Solution:
1) Write the dissociation equation for Th(OH)4 and its Ksp expression:
Th(OH)4 ⇌ Th4+ + 4OH¯
Ksp = [Th4+] [OH¯]4
2) Substitute into the Ksp expression and solve:
Ksp = 10¯50.52 = 3.0 x 10¯513.0 x 10¯51 = (s) (4s)4
256s5 = 3.0 x 10¯51
s = 2.6 x 10¯11 M
Solving Ksp Problems:
Part One - s2Solving Ksp Problems:
Part Two - 4s3Solving Ksp Problems:
Part Three - 27s4Solving Ksp Problems:
Part Four - 108s5Back to Equilibrium Menu