The value of the solubility product, Ksp, of iron(III) hydroxide, Fe(OH)₃, is given by the following expression. Ksp = [Fe³⁺][OH⁻]³ = 2.0 × 10⁻³⁹ mol⁴ dm⁻¹²

1. (a)(i)Calculate the solubility of Fe(OH)₃ in water. solubility = .............................................. mol dm⁻³ [1][1]
2. (a)(ii)Calculate the solubility of Fe(OH)₃ in 0.010 mol dm⁻³ barium hydroxide, Ba(OH)₂(aq). solubility = .............................................. mol dm⁻³ [2][2]
3. (a)(iii)Fe(OH)₃ is less soluble in Ba(OH)₂(aq) than it is in pure water. Name this effect. [1][1]
4. (b)The numerical value of the Kₐ of HBrO is 2.00 × 10⁻⁹. X is a solution of HBrO which contains 4.00 × 10⁻³ mol of HBrO in 100 cm³ of solution. In this solution the following equilibrium is established in which there are two conjugate acid-base pairs. HBrO + H₂O ⇌ BrO⁻ + H₃O⁺
5. (b)(i)Define conjugate acid-base pair. [1][1]
6. (b)(ii)Identify the two conjugate acid-base pairs shown in the equation above. pair one acid .............................................. base .............................................. pair two acid .............................................. base .............................................. [1][1]
7. (b)(iii)Calculate the pH of solution X. Show all your working. pH = .............................................. [2][2]
8. (b)(iv)A solution containing 2.00 × 10⁻³ mol of NaOH is added to solution X. A buffer solution is formed. Calculate the pH of this buffer solution. pH = .............................................. [1][1]