CHEM 1312 Lecture Notes - Lecture 8: Hydrolysis, Stoichiometry, Lead
Chapter 17 pt 2: Acid-Base Equilibria
and Solubility Equilibria
• solubility rules introduced in chapter 9:
• view presented in chapter 9 a little too simplistic
-- the most soluble compounds can be made
insoluble if you put enough solute in
-- the most insoluble compounds can be made
soluble if you put little enough solute in
• better view: gradient of solubilities
• use concept of equilibrium to get the gradient
ClO4–
O2–
Ca2+, Sr2+
SO32–
TABLE 9.2
TABLE 9.3
Solubility Equilibria:
AgCl (s) Ag+ (aq) + Cl– (aq) (saturated salt
solution)
• write equilibrium expression:
Kc = [Ag+][Cl–] = Ksp (solubility product)
Ag2CrO4 (s) 2 Ag+ (aq) + CrO4
– (aq)
Ksp = [Ag+]2 [CrO4
–]
• in general: MXn (s) Mn+ (aq) + nX− (aq)
• important points:
-- Solids not included in Ksp
-- always write Ksp expression with solid on left
-- have to pay attention to stoichiometry again!
• Molar solubility – number of moles of solute in 1 L of a
saturated solution (mol L–1)
• Solubility - number of grams of solute in 1 L of a saturated
solution (g L–1)
• Ksp can be used to determine molar solubility (and solubility)
-- handle as an equilibrium problem
-- Use ICE table
Larger Ksp values indicate more soluble compounds
• Molar solubility can be used to determine the value of the Ksp
nn
K]][X[M -
sp
+
=
Document Summary
Chapter 17 pt 2: acid-base equilibria and solubility equilibria: solubility rules introduced in chapter 9: Ca2+, sr2: view presented in chapter 9 a little too simplistic. - the most soluble compounds can be made insoluble if you put enough solute in. - the most insoluble compounds can be made soluble if you put little enough solute in: better view: gradient of solubilities, use concept of equilibrium to get the gradient. Ag+ (aq) + cl (aq) (saturated salt solution: write equilibrium expression: Mn+ (aq) + nx (aq: important points: - always write ksp expression with solid on left. Larger ksp values indicate more soluble compounds: molar solubility can be used to determine the value of the ksp. Determine the ksp for agbr if you can dissolve 8. 8x10 7 moles into water to form 1 l of solution: The molar solubility of ag2cro4 is 6. 7x10 5 m at 25 c. At 25 c, what is the molar solubility of pbi2 (ksp =