Given: Solubility of Cu(OH)2 is 3.42 X 10-7 mol/L
Required: Calculate the Ksp for Cu(OH)2
Solution:
1. Write Equation: Cu(OH)2 (s) Û Cu2+ (aq) + 2 OH-(aq)
2. Prepare chart Initial Conc. - 0 0
Change - +3.42 X 10-7 +2(3.42 X 10-7)
Equilibrium - 3.42 X 10-7 6.84 X 10-7
3. Calculate Ksp
Ksp = [Cu2+][OH-]2
Ksp = [3.42 X 10-7][6.84 X 10-7]2
Ksp = 1.6 X 10-19
Your turn
Given: solubility of Fe(OH)3 is 9.9 X 10-11 mol/L
Required: calculate the Ksp of Fe(OH)3
1. Write equation Fe(OH) (s) Û
2. Prepare chart Initial Conc.
Change
Equilibrium
3. Calculate Ksp
Calculating Solubility from Ksp
Given: Ksp of AgCl = 1.8 X 10-10
Required: solubility of AgCl in pure water
Solution:
1. Let the solubility of AgCl (s) be x mol/L
2. Write equation AgCl (s) Û Ag+ (aq) + Cl- (aq)
3. Prepare chart Initial
Change
Equilibrium
4. Fill in chart
Ksp = [Ag+][Cl-]
1.8 X 10-10 =
x =
Therefore the solubility of AgCl (s) in pure water is ___________ mol/L
Therefore, ______ mol of AgCl dissolves in 1 L of solution, and the equilibrium concentration of the Ag+ ions = ________ mol/l and the equilibrium concentration of the Cl- ions is _______ mol/L.
Problems p. 491 #1-3
For 2 (b) mol X g = g = mg
L mol L mL
I.e. g X 1000 mg X 1 L = mg
L 1 g 1000 mL mL