Lithia Water Analysis Module
Solubility Equilibria
Assessment Question Set #1
Q1. Write the balanced reaction for the dissolution of iron (III) hydroxide in water.
Q2. Write the equilibrium constant expression for the solubility of iron (III) hydroxide.
Q3. Calculate the molar solubility of iron (III) hydroxide in pure water.
Q4. Calculate the molar solubility of iron (III) hydroxide at pH 6.4, and compare it to the calculated molar
solubility of iron (III) hydroxide in Q3.
Q5. Calculate the molar solubility of iron (III) hydroxide at pH 6.4 when the ionic strength of the solution
is 0.10 mol L-1.
Q6. To prevent precipitation of iron (III) hydroxide in household water systems, hydrogen peroxide is
often added as an oxidizing agent to municipal water sources containing iron (II) ion concentrations
above 0.3 mg L-1. Compare the effectiveness of this treatment at pH 6.4 versus pH 2.0 at a dissolved
iron (i.e. Fe2+) concentration of 0.3 mg L-1.