• For solids dissolving to form aqueous solutions

         ○ Ksp = solubility product constant =

                    ■ Ksp value depends on ion concentration → more cations & anions = higher value

                    ■ Solids not included in equilibrium expression because their concentration do not change

                    ■ Only affected by temp

  • Solubility = s = concentration of solid that dissolves

          ○ Solubility has the same units as molarity (moles/liters)

         ○ Solubility can vary with different factors → can speed or slow down the attainment of equilibrium but not its value

                 ■ Ex: Speed up by increasing surface area (grinding up the solid or stirring the solution); decrease as with common ion effect

Solubility Product Practice

  • Type 1: Given solubility → calculate Ksp value

            1. Write out balanced equation & ICE table

                 ○ S instead of x → solubility is our s that will plug in 

  • Type 2: Given Ksp → calculate solubility:

           2. Write out balanced equation and ICE table

             ○ Solve for s

Relative Solubilities

  • In questions, will be given salts and must be able to decide which one is more soluble/greater molar solubility
  • Ksp will only allow us to compare the solubility of salts that fall apart into the same number of ions

            ○ Bigger Ksp value = more soluble 

            Ex: same number of ions so can compare

             Ex:  diff number ions so can’t use Ksp to compare

                    ■ Will have to solve for solubility (s) and compare those → bigger s value = more soluble

Calculations Involving Precipitation/Will a Precipitate Form?

  • Must calculate Q and compare it to Ksp


  • Focus on the compound whose Ksp value has been given and write balanced equation for how it breaks up
  • Steps: 
  1. Set up Q using FINAL Molarity (if not given use M1V1 = M2V2)

               ■ Do M1V1 = M2V2 for both solutions → plug in the 2 M2 into Q

                     Note: V2 = volume of the 2 solutions combined; M2 = concentration of the ion

  • Q > Ksp → Precipitation
  • Q < Ksp → No precipitate
  • Q = Ksp → Equilibrium